Particles doi: 10.3390/particles9020049

Authors: Ivan D. Markozov Alexander Y. Potekhin Alexander D. Kaminker Alexander A. Mushtukov

Radiation of X-ray pulsars is powered by accretion on the neutron star surface from a binary companion under the influence of a strong magnetic field. We study the beaming of this radiation in the case of subcritical X-ray pulsars, where it is formed in the accretion channel close to the neutron star surface. We solve equations of the hydrodynamics and radiative transfer of two coupled polarization modes in the accretion channel numerically, taking into account resonant Compton scattering and vacuum polarization. The beaming patterns are obtained for different accretion rates, photon energies, and polarizations, as well as for different models of the neutron star surface radiation. The calculated beaming patterns are converted into light curves for both the intensity and polarization, taking into account the effects of General Relativity. These beaming patterns and light curves are found to be strongly affected by the resonant Compton scattering for photon energies comparable with the electron cyclotron energy. In particular, the angular redistribution of radiation near the cyclotron resonance may reduce the light-curve modulation amplitude, which is consistent with observational indications of a suppressed pulsed fraction at these energies.

Particles doi: 10.3390/particles9020048

Authors: Cheng Yin Chengjian Lin Lei Yang Feng Yang Huiming Jia Nanru Ma Peiwei Wen Tianpeng Luo

The reaction dynamics of weakly-bound nuclear systems at near-barrier energies is a compelling topic in nuclear physics. This review summarizes decades of experimental work by the Nuclear Reaction Group at the China Institute of Atomic Energy. Using transfer reactions with the distorted wave born approximation and asymptotic normalization coefficient analyses, we confirm the first excited neutron halo (13C) on the β-stability line and identified new halo states in 12B. Total reaction cross-section measurements revealed proton halo nuclei 27P and 29S, with core enlargement observed in 27P and 28P. We established conditions for halo formation and delineated the proton halo existence region. In two-proton emission studies, we observed 2He cluster emission from highly excited 17,18Ne and 28,29S, with 29S being the second such case internationally. In β-delayed decay, we discovered β2p emission in 22Si and determined its mass, observing isospin-symmetry breaking in 20Mg, 22Si, and 27S. Decay schemes for 27S and 26P addressed the 26Al abundance problem. For nuclear interactions, we investigated the 6He optical potential, finding the dispersion relation inapplicable for 6He + 209Bi, and developed notch and Bayesian methods to constrain uncertainties. For unstable nuclei, the proton drip-line systems 8B and 17F have been intensively studied via complete kinematics measurements of the 8B + 120Sn and 17F + 58Ni reactions, respectively. The results show that elastic breakup dominates for proton-halo 8B, while inelastic breakup prevails for 17F, with proton-rich nuclei exhibiting lower breakup probabilities than neutron-halo nuclei due to Coulomb effects. Fusion studies revealed sub-barrier enhancement in 17F + 58Ni from continuum couplings. We propose direct fusion–evaporation measurements with deflection systems integrated with breakup detection to disentangle complete and incomplete fusion channels.

Particles doi: 10.3390/particles9020047

Authors: Dimitar Tonev Galina D. Dimitrova Anguel Demerdjiev Giovanni De Gregorio Giacomo de Angelis Elena Geleva Nikolay Goutev Nikolay N. Petrov Ivaylo Pantaleev Lilianna Panteleev-Simeonova

Advanced Doppler-shift methods for the calculation of the γ-ray lineshape registered in recoil-distance Doppler-shift and Doppler-shift attenuation methods are presented, emphasizing the case using a gate set on the shifted part of a direct feeding transition. For the precise description of the γ-ray lineshape, the process of evaporation of light particles from the compound nucleus has to be taken into account in the case of heavy ion-induced fusion-evaporation reactions. In addition, the impact of different approaches for calculating stopping powers is investigated in the process of the lifetime determinations. In the RDDS experiments, the γ-emission during the slowing down in the stopper is discussed in detail. Applications of the new procedures are demonstrated in two experiments: the first one is a plunger experiment performed in order to check for chirality in the 134Pr nucleus and the second one is a DSAM experiment conducted to test the isospin symmetry in 31P and 31S mirror nuclei.

Particles doi: 10.3390/particles9020046

Authors: Feng-Kun Guo Christoph Hanhart Alexey Nefediev

Radiative decays of hadronic states provide an essential source of information that can facilitate deciphering their nature and properties. However, a lot of confusion concerning radiative decays of hadronic molecules and their interpretation can be found in the literature. In this paper, we briefly review several types of such decays and pinpoint similarities and essential differences between them. In particular, we emphasise the crucial role played by the hierarchy of the scales relevant to the studied system and the resulting necessity of employing an approach that considers them appropriately. We illustrate the situation with several instructive examples.

Particles doi: 10.3390/particles9020045

Authors: Laura Xiomara Gutiérrez-Guerrero Roger José Hernández-Pinto

We present an updated overview of the symmetry-preserving contact interaction model in hadronic physics, which was developed a little over a decade ago to describe the mass spectrum and internal structure of mesons and diquarks composed of light and heavy quarks. Over the years, the contact interaction model has evolved into a framework capable of treating both ground and excited states, providing a simple yet consistent approach to nonperturbative QCD. In this review, we examine the mass spectrum and elastic form factors of forty mesons with different spins and parities, together with their corresponding diquark partners. Importantly, we update the comparison of contact interaction predictions using recent results from the literature, offering a fresh perspective on the model’s performance, strengths, and limitations. The analysis presented here refines previous conclusions and supports the contact interaction model as a practical tool for hadron structure studies, with potential applications to baryons and multiquark states. We also present comparisons with other theoretical models and approaches, including lattice quantum chromodynamics, and comment on future prospects in view of ongoing and planned experimental programs regarding hadron structure. In particular, forthcoming measurements at FAIR together with future studies at Jefferson Lab and the Electron Ion Collider are expected to provide key insights into hadron structure, with FAIR offering indirect constraints via hadron spectroscopy, hadronic interactions, and in-medium properties; high-precision data on meson structure and form factors from Jefferson Lab and the Electron Ion Collider will provide valuable benchmarks with which to confront predictions based on the contact interaction model.

Particles doi: 10.3390/particles9020044

Authors: Mihail Chizhov Emanuil Chizhov Daniela Kirilova Momchil Naydenov

We present a short review dedicated to low-lying meson states. We present all meson nonets, which consist from up, down and strange light quarks. We consider the scalar nonet as a basic nonet. We work in the framework of the massless Nambu–Jona-Lasinio UR(3)×UL(3) quark model. The collective meson states are described through initially bare quark–antiquark pairs, whose condensates lead simultaneously to spontaneous breaking of the chiral and the flavour symmetry. After quantisation and the spontaneous breaking of the chiral symmetry, when quarks obtain constituent nonzero masses, they become dressed. We present an explanation of the inverse mass hierarchy of the low-lying nonet of the scalar mesons. The proposed explanation is based on symmetry principles. It is shown that, due to the flavour symmetry breaking, two isodoublets of K0*(700) mesons play the role of Goldstone bosons. It is also proven that there exists a solution with almost degenerate masses of the a0(980) and f0(980) mesons and a zero mass of the f0(500) meson. Short description of the physical properties of other meson nonets is provided. In particular unique mass relations among the different nonets, which are experimentally confirmed, are presented.

Particles doi: 10.3390/particles9020043

Authors: Thomas Riedel

We report a curious numerical observation: If atomic nuclei are modelled as connect-sums of threefoil knots with alternating chirality, the ropelength of the composite knot—a purely geometric quantity requiring no quantum mechanics—tracks the experimental binding-energy curve from hydrogen to uranium. A two-parameter fit to 50 nuclei gives R2=0.9998 (coefficient of determination; 1 = perfect fit) and RMS=6.9MeV (root-mean-square deviation between model and experiment), comparable to the five-parameter Bethe–Weizsäcker formula (RMS=8.3MeV) at less than half the parameter count. Out-of-sample predictions for Pu244 and Cf252, not used in the fit, are accurate to 0.4MeV and 8.4MeV, respectively. What makes the observation worth reporting is not the fit itself, but the range of nuclear phenomenology that emerges uninstructed from the topology: saturation, surface energy, isospin pairing, odd-even staggering, and geometric analogues of nuclear isomers all appear as consequences of the connect-sum construction, without additional assumptions. We catalogue these correspondences, assess which are structural and which may be coincidental, and identify concrete numerical tests that would distinguish the two possibilities.

Particles doi: 10.3390/particles9020042

Authors: Alexandre Deur Stanley J. Brodsky Craig D. Roberts Balša Terzić

In quantum field theory, the vacuum is popularly considered to be a complex medium populated with virtual particle + antiparticle pairs. To an observer experiencing uniform acceleration, it is generally held that these virtual particles become real, appearing as a gas at a temperature that grows with the acceleration. This is the Unruh effect. However, it has been shown that vacuum complexity is an artifact produced by treating quantum field theory in a manner that does not manifestly enforce causality. Choosing a quantization approach that patently enforces causality, the quantum field theory vacuum is barren, bereft even of virtual particles. We show that acceleration has no effect on a trivial vacuum; hence, there is no Unruh effect in such a treatment of quantum field theory. Since the standard calculations suggesting an Unruh effect are formally consistent, insofar as they have been completed, there must be a canceling contribution that is omitted in the usual analyses. We argue that it is the dynamical action of conventional Lorentz transformations on the structure of an Unruh detector.

Particles doi: 10.3390/particles9020041

Authors: Bhupendra Kumar Shukla Deger Sofuoğlu Aroonkumar Beesham Rishi Kumar Tiwari Mfanafuthi Siyabonga Msweli

The evolution of the deceleration parameter q(z) plays a crucial role in understanding the dynamics of dark energy within the framework of modern cosmology. In this study, we perform a parametric reconstruction of q(z) in a spatially flat Friedmann–Robertson–Walker (FLRW) Universe composed of radiation, pressureless dark matter, and dark energy. We consider a physically motivated form of q(z) that effectively describes the transition of the Universe from a decelerating to an accelerating expansion phase. This parametrization is incorporated into the Friedmann equations to derive the corresponding Hubble parameter, which is then confronted with a comprehensive set of observational data, including Hubble parameter measurements H(z), Type Ia supernovae (SNIa), and Baryon Acoustic Oscillations (BAO) data. Employing the Markov Chain Monte Carlo (MCMC) approach, we constrain the model parameters using the combined H(z)+SNIa+BAO dataset. The best-fit parameters are subsequently used to reconstruct the cosmographic quantities, such as the deceleration, jerk, and snap parameters, which provide deeper insight into the expansion history of the Universe. Finally, a comparative analysis with the standard ΛCDM model is carried out to assess the compatibility and effectiveness of the proposed parametrization.

Particles doi: 10.3390/particles9020040

Authors: Qiang Wang You-Bao Wang Jun Su Zhi-Yu Han B. Alex Brown Li-Hua Chen Zi-Qiang Chen Bao-Qun Cui Bo Dai Tao Ge Xin-Yue Li Yun-Ju Li Zhi-Hong Li Gang Lian Yin-Long Lyu Rui-Gang Ma Tian-Li Ma Xie Ma Ying-Jun Ma Yi Su Bing Tang Chun-Guang Wang Hong-Yi Wu Fu-Rong Xu Sheng-Quan Yan Sheng Zeng Hao Zhang Yun Zheng Chao Zhou Yang-Ping Shen Bing Guo Tian-Jue Zhang Wei-Ping Liu

20Na is a well-known β-delayed α emitter, owing to the large decay energy of 20Na above the α + 16O threshold in the A=5α daughter nucleus 20Ne. In this work, the decay property of 20Na is investigated in detail via the β-γ β-α and β-γ-α coincidence spectroscopy. As the day-one experiment of the Beijing Rare Isotope Facility (BRIF), the intense 20Na beam was produced using the Isotope Separator On Line (ISOL) technique through the 100 MeV proton bombarding a stack of MgO as a thick target. Specific interest was focused on the exotic decay mode of 20Na; the previously reported low-energy α lines at 713 and 846 keV were confirmed, and several weak β-γ-α decay sequences were clearly identified for the first time, thanks to the strong resolving power of α-γ coincidence spectroscopy. The decay properties of 20Na are compared to the shell model calculation, which agree reasonably well with the allowed β transition strengths and subsequent electro-magnetic transitions with the use of the sd shell-model space with the USDB interaction.

Particles doi: 10.3390/particles9020039

Authors: Felix Karbstein

In this article, we show that the well-known leading low-temperature correction to the Heisenberg–Euler Lagrangian in a constant electromagnetic field arising at two loops can be efficiently extracted from its one-loop zero-temperature analogue. Resorting to the real-time formalism of equilibrium quantum field theory that explicitly separates out the zero-temperature contribution from the finite-temperature corrections, the determination becomes essentially trivial. In essence, it only requires taking derivatives of the Heisenberg–Euler Lagrangian at one loop and zero temperature for the field strength. As a bonus, we then effectively dress the low-temperature contribution at two loops by one-particle reducible tadpole structures. This generates a subset of higher-loop contributions to the Heisenberg–Euler Lagrangian in the limit of low temperatures. We extract their leading strong-field behavior at a given loop order, and finally resum these to all loop orders.

Particles doi: 10.3390/particles9020038

Authors: Li-Sheng Geng Jun-Xu Lu Qing-Yu Zhai Zhi-Wei Liu Shi-Hang Shen

The nuclear force is central to our understanding of complex nuclear phenomena and to the applications of nuclear techniques. The non-perturbative nature of low-energy strong interaction and color confinement have provided an ab initio understanding of nuclear force, a challenge for almost a century, since the pioneering work of Yukawa. Since 1990, chiral effective field theory (ChEFT) has become the de facto standard for describing nuclear interactions; most prior studies employed heavy-baryon chiral perturbation theory. Only recently, there have been successful attempts to construct a chiral nuclear force employing covariant baryon chiral perturbation theory. In this work, we review recent developments and applications of relativistic chiral nuclear forces. We first elaborate on the necessity of relativistic/covariant theories, then present the construction of the first high-precision relativistic chiral nuclear force up to next-to-next-to-leading order (NNLO), and discuss the ongoing progress in higher-order nucleon–nucleon (NN) and n-d scattering, as well as their applications in nuclear matter, finite nuclei, and hypernuclear systems. Finally, we summarize the achievements and outline the future outlook of this research field.

Particles doi: 10.3390/particles9020037

Authors: Dragana Pilipović

The derivations presented in this paper suggest an intimate relationship between geometry and the electroweak sector at the Planck scale. A Lorentz-invariant maximally symmetric stochastically perturbed spacetime transformed to spherical coordinates reveals an emergent Schwarzschild metric, entirely a statistical structure of stochastic spacetime. Similarly, the transition from a maximally symmetric universe with a complex SU(2) scalar doublet ϕ, comprising four independent real scalar fields with a zero vacuum expectation value (VEV), to spherical coordinates at the Planck scale reveals the spontaneously broken electroweak (EW) sector. Working in the unitarity gauge, the resulting EW potential can be simultaneously mapped in space at the Planck scale and across the EW sector. In space, the resulting EW potential includes a deep well within the Schwarzschild sphere and a shallow well just outside corresponding to an accretion disk. The same potential mapped in the EW space provides an entire family of possible sombrero hat potentials with fourth-order coupling specific to a point in space. At the minimum points of the potential in space, inside the Schwarzschild sphere and at the accretion disk, the λ corresponding to the Standard Model (SM) fourth-order coupling is instead derived as λ5. The factor of 15 is a simple consequence of the conservation of the EW VEV and the fact that the SM formulation of the EW potential does not account for situations where the perturbations in ϕ dominate. A more general formulation of the EW potential restores the SM quartic coupling and preserves λ in space. An emergent Higgs field inside the Schwarzschild black hole is found to directly relate to the stochastic spacetime fields normalized by the Schwarzschild radius. The corresponding Higgs vacuum has both a ground and excited state and the possibility of both positive and negative vacuum entropy. Finally, the scalar-field VEV degeneracy in EW space of the metastable Higgs vacuum appears instead differentiated in space with possible probability, tunneling, and entropy implications.

Particles doi: 10.3390/particles9020035

Authors: Yuheng Wu Linkai Li Yuheng Xing Xinxing Wu Yue Tan

Experimentally, the 1+ state X(3872) was first discovered, and subsequently, its partner state Y(4260), with the same quark content (cq¯qc¯) and quantum number 1− was also observed. Inspired by this pattern, we systematically investigate the newly discovered 1+ state Tcc and its possible 1− partner, the TDD1 system with the same quark content (cq¯cq¯). Within the framework of the chiral quark model, we perform a comprehensive study of the bound and resonance states of TDD1 using the Gaussian expansion method (GEM). Two quark configurations, the molecular structure and the diquark structure, are considered in our calculations. Our results indicate the existence of a shallow bound state dominated by the DD1* channel, which is analogous to the experimentally observed Tcc, as well as two compact resonant states with narrow widths around 4.5 GeV. To avoid the influence of model parameters on the results, we additionally fitted a new set of parameters and obtained consistent conclusions. According to our calculation results, although the color-octet and diquark configurations have relatively high energies, the channel-coupling effects induced by them play a crucial role in the formation of these stable states. We strongly encourage experimental efforts to search for the stable states predicted in the TDD1 system.

Particles doi: 10.3390/particles9020036

Authors: Kaiyuan Zhang Ling Li Jie Yan Guixiang Ye Xinhui Wu Jia-Lin An Shi-Sheng Zhang Cong Pan Xiang-Xiang Sun

The experimental exploration of halo nuclei over the past four decades has established ground-state halo phenomena in about twenty nuclei, providing important benchmarks for modern nuclear theories. The deformed relativistic Hartree–Bogoliubov theory in continuum (DRHBc) has been successfully applied to describe known halo nuclei and to predict new candidates during the last dozen years. In this work, the possible two-neutron halo nuclei F29 and F31 are investigated within the DRHBc framework. In the spherical limit, an inversion between the 2p3/2 and 1f7/2 orbitals is obtained relative to the conventional single-particle ordering, which plays a crucial role in the formation of deformed halos in these nuclei. Assuming a prolate deformation with β2≈0.4, as suggested in previous studies, a deformed two-neutron halo in F29 is reproduced. For F31, a well-deformed ground state with β2≈0.24 and a more pronounced two-neutron halo emerge self-consistently.

Particles doi: 10.3390/particles9020034

Authors: Oscar Adriani Eugenio Berti Pietro Betti Lorenzo Bonechi Massimo Bongi Raffaello D’Alessandro Sebastiano Detti Elena Gensini Elena Geraci Maurice Haguenauer Vlera Hajdini Cigdem Issever Yoshitaka Itow Katsuaki Kasahara Haruka Kobayashi Clara Leitgeb Yutaka Matsubara Hiroaki Menjo Yasushi Muraki Andrea Paccagnella Paolo Papini Giuseppe Piparo Sergio Bruno Ricciarini Takashi Sako Nobuyuki Sakurai Monica Scaringella Yuki Shimizu Tadashi Tamura Alessio Tiberio Shoji Torii Alessia Tricomi Bill Turner Kenji Yoshida

The Large Hadron Collider forward (LHCf) experiment studies the production of neutral particles in the very forward region of high-energy hadronic collisions at the LHC. These measurements provide essential calibration data for hadronic interaction models used in simulations of extensive air showers initiated by ultra-high-energy cosmic rays. The LHCf experiment measures forward-produced neutral particles, such as neutrons, photons, π0, and η mesons, which play a key role in the development of extensive air showers. Proton–proton collisions at the LHC reach center-of-mass energies up to 13.6 TeV, corresponding in the fixed-target frame to cosmic-ray interactions at energies close to 1017 eV in the Earth’s atmosphere. LHCf has collected data in proton–proton collisions at several energies, as well as in proton–lead collisions, enabling detailed comparisons between experimental results and predictions of hadronic interaction models. This contribution reviews the most significant LHCf results, with emphasis on Run II proton–proton data at s=13TeV, including measurements of forward neutron, photon, and η meson production. Finally, future prospects are discussed, focusing on ongoing analyses of Run III proton–proton data at s=13.6TeV and on the final LHCf operation in proton-oxygen collisions at sNN=9.6TeV, which best reproduces cosmic-ray interactions with nuclei of the Earth’s atmosphere.

Particles doi: 10.3390/particles9020033

Authors: Constantino Tsallis

On the basis of the correlations of distant—in time and/or in space—elements of a many-element system, we propose the hard core of a mathematical definition of what may be referred to as complexity. This definition consistently leads to the concept of degree of complexity.

Particles doi: 10.3390/particles9020032

Authors: Lei Ni Yu Jin Hui Hua Zhihuan Li

Experimental studies on the spontaneous nucleon emission in nuclei around the drip line enable us to explore new isotopes or resonant states, and to reveal exotic structures and decay properties of nuclei located far from the β stability line; consequently, they are of critical importance for probing limits of nuclear stability and understanding nucleon–nucleon interactions under extreme conditions of isospin asymmetry. With the radioactive isotope beam 20Mg provided by the National Superconducting Cyclotron Laboratory at Michigan State University, we studied the proton decays of nuclei around the proton drip line at A∼20 mass region. Complete-kinematics measurements were performed for proton decays of one-proton resonant states in 18Na, two-proton resonant states in 20Mg, three-proton resonant states in 21Al, and four-proton resonant states in 18Mg, yielding decay energy spectra for all four nuclei. With the invariant mass method, the ground state of 18Na was firmly identified, clarifying previous ambiguities of its position. The isotope 18Mg, which is located two neutrons beyond the proton drip line, was experimentally observed for the first time. Multi-body correlation analysis of emitted protons from 20Mg, 21Al, and 18Mg, combined with Monte Carlo simulations, reveals that the identified resonant states in 20Mg and 21Al predominantly decay via two and three sequential steps of 1p emission, respectively, whereas the 18Mg ground state decays mainly through a two-step cascade of prompt 2p emission.

Particles doi: 10.3390/particles9020031

Authors: Takayuki Yamaguchi Yoshitaka Yamaguchi Tetsuya Ohnishi Daisuke Nagae Yury A. Litvinov

Heavy radioactive ion beams produced by in-flight techniques often involve long-lived excited states (isomers). This presents a challenge for reaction studies because none of the existing fragment separators worldwide can resolve isomers in-flight. Here, we propose a novel scheme to produce tagged cocktail beams or pure isomer beams using an ion storage ring. The mass resolving powers of storage rings enable us to identify and separate ions of the isomeric state from the corresponding ground state in a secondary beam. For short-lived isomers, the Rare-RI Ring (R3) facility at the RI Beam Factory (RIBF) will be available, while for long-lived isomers the Experimental Storage Ring (ESR) at the GSI/FAIR facility will be utilized. Isomers often have spins and deformations significantly different from the ground states. Studying isomer structures will provide unique insight into their specific interactions, opening a new frontier in reaction studies with radioactive ion beams in the coming years.

Particles doi: 10.3390/particles9020030

Authors: Fabio Muleri Stefano Cesare Enrico Costa Walter Cugno Klaus Desch Alessandro Di Marco Sergio Fabiani Riccardo Ferrazzoli Markus Gruber Daniel Heuchel Saba Imtiaz Jochen Kaminski Dawoon Edwin Kim Alessandro Lacerenza Carlo Lefevre Hemanth Manikantan Vladislavs Plesanovs John Rankin Ajay Ratheesh Alda Rubini Paolo Soffitta

The successful detection of X-ray polarization from many celestial sources belonging to different classes by the IXPE mission has opened a new window in X-ray astronomy. While an impressive number of scientific topics have already been addressed by IXPE, many of them would benefit from a new class of instrumentation that could be launched on a relatively short time scale. In this contribution, we present the development activities of a focal-plane polarimeter whose goal is to extend the energy range of IXPE up to tens of keV, with better sensitivity and lower background. Our design is based on the use of multilayer mirrors and stacked instrumentation, comprising either a low- or medium-energy imaging photoelectric polarimeter and an active Compton polarimeter. Such an approach relies on hardware with flight heritage and—although still under development for the specific application in X-ray polarimetry—it has the potential to answer compelling scientific questions and to soon become competitive from the point of view of feasibility for space applications.

Particles doi: 10.3390/particles9010029

Authors: Huang-Jing Zheng Sheng-Qin Feng

Relativistic heavy-ion collisions generate ultra-strong magnetic fields that interact with the quark–gluon plasma (QGP), a key focus of high-energy physics research. This study investigates QGP energy density evolution under time-dependent magnetic fields within a (1 + 1)D relativistic magnetohydrodynamic (RMHD) framework integrated with Bjorken flow. Three magnetic field temporal evolution models (Type-1, Type-2, Type-3) are analyzed for two different equations of state: (1) p=cs2e (simplified ultra-relativistic), and (2) p=cs2e−2MB (magnetized conformal), incorporating a temperature-dependent magnetic susceptibility derived from lattice QCD. Results show that stronger magnetic fields consistently suppress QGP energy density decay, with suppression magnitude dependent on the magnetic field’s temporal profile. Ultra-relativistic fluids exhibit slowed energy decay due to magnetic pressure counteracting hydrodynamic expansion. In contrast, magnetized conformal fluids display faster energy dissipation under identical conditions, arising from the synergistic effect of enhanced magnetic fluid coupling, increased energy dissipation during interaction, and QGP’s perfect fluid expansion at elevated temperatures. Temperature-dependent magnetic susceptibility reveals a transition from diamagnetic (confined phase) to paramagnetic (deconfined QGP phase) behavior, introducing a feedback mechanism that strengthens energy retention at higher temperatures. This work clarifies the interplay between magnetic field dynamics, QCD phase structure, and hydrodynamic expansion, providing key observational signatures for distinguishing fluid types in heavy-ion collisions and advancing realistic modeling of magnetized QGP.

Particles doi: 10.3390/particles9010028

Authors: Tamás Biró

We report on laser fusion research with nanotechnology-improved targets embedded in special polymers. The results of the last three years are reviewed here, including laser matter interaction craters, laser infrared breakdown spectroscopy, and Raman spectroscopy results, as well as a selected Thomson parabola image showing protons accelerated up to 300 keV. In this paper, we focus on proton acceleration and plasmonic enhancement mechanisms rather than on the direct demonstration of sustained fusion reactions.

Particles doi: 10.3390/particles9010027

Authors: Zheyang Lin Zaihong Yang

This review summarizes recent experimental progress in the structure and correlations of light neutron-rich nuclei. We first highlight achievements based on quasi-free scattering reactions in inverse kinematics at the Radioactive Isotope Beam Factory (RIBF), including investigations of the single-particle composition of halo systems—for example, revealing the minimal s-wave component in the “weak-halo” nucleus 17B—and the mapping of universal, surface-localized dineutron correlations in Borromean nuclei such as 11Li, 14Be and 17B. We then discuss recent advances in the study of multineutron correlations and cluster states, addressing both experimental challenges and major breakthroughs. These include the observation of a candidate 4n resonance, the absence of a resonant state in the 3n system, the characterization of direct two-neutron decay in 16Be, and evidence for a condensate-like α+n2+n2 cluster structure in the He8(02+) state. Finally, we discuss prospects for extending such investigations to heavier halo candidates and more complex multineutron systems, and outline the development of next-generation neutron detector arrays that will drive future progress in this field.

Particles doi: 10.3390/particles9010026

Authors: Yuwen Chen Wei Nan Bing Guo Chengjian Lin Bing Tang Danyang Pang Lei Yang Dongxi Wang Guo Yang Yangping Shen Qiwen Fan Yiwen Bao Lei Cao Lihua Chen Baoqun Cui Yueming Hu Qinghua Huang Huiming Jia Chaoxin Kan Kangning Li Yaoqian Li Yunju Li Zhihong Li Gang Lian Junhui Liao Zhenwei Liu Tianpeng Luo Nanru Ma Ruigang Ma Xie Ma Yingjun Ma Guofang Song Lei Wang Xiaofei Wang Youbao Wang Yuheng Wang Peiwei Wen Shengquan Yan Feng Yang Sheng Zeng Yifan Zhang Tianjue Zhang Weiping Liu

Present and future rare isotope accelerator facilities provide new opportunities to explore the structure of unstable nuclei. We report the measurements of the elastic scattering angular distributions of 21Na and 22Na on the doubly magic 40Ca above the Coulomb barrier energies, using high-purity post-accelerated ISOL beams from Beijing Radioactive Ion Beam Facility (BRIF). Angular distributions were measured with a silicon detector telescope array, and relative cross sections were determined with a CaF2 target on Au backing. The data were well reproduced by optical model calculations with Woods–Saxon and USNP potentials, the latter giving better agreement. These results confirm the stable operation and performance of the BRIF ISOL production and post-acceleration system, demonstrate its capability to provide radioactive beams of useful intensity and purity for future investigations of reaction dynamics and astrophysically relevant processes involving proton-rich nuclei, and simultaneously extend proton-rich elastic scattering studies to heavier systems.

Particles doi: 10.3390/particles9010025

Authors: Shihang Shen Serdar Elhatisari Dean Lee Ulf-G. Meißner Zhengxue Ren

We present an ab initio study on the one-neutron halo nucleus 11Be using nuclear lattice effective field theory with high-fidelity chiral interactions at N3LO. By employing the wavefunction matching method to mitigate the sign problem and the pinhole algorithm to sample many-body correlations, we successfully reproduce the ground-state parity inversion and the extended matter radius characteristic of the halo structure. We analyze the intrinsic density distributions and geometric shapes of 11Be in comparison with the core nucleus 10Be. Our results reveal a prominent two-cluster structure in both nuclei and the occupation of the σ molecular orbital by the valence neutron in 11Be. It enhances the prolate deformation as well as the diffuse neutron tail, distinct from the π-orbital occupation observed in the 10Be ground state.

Particles doi: 10.3390/particles9010024

Authors: Arisa Wada

With the conclusion of proton–proton collision data-taking in 2025, the ATLAS experiment has now integrated a luminosity exceeding 300 fb−1 during the Run 3 period, which began in July 2022 following Long Shutdown 2 (LS2). During LS2, a series of detector upgrades were implemented, including the installation of the New Small Wheel (NSW) in the innermost stations of the Muon Spectrometer end-caps. The ATLAS Muon Spectrometer, the largest muon system ever built at a collider, now comprises both established gaseous detectors—Monitored Drift Tubes, Thin Gap Chambers, and Resistive Plate Chambers—and newer detectors like Micromegas and small-strip TGCs in the NSW. These new systems are now in stable operation following an extensive phase of construction and commissioning, providing enhanced muon tracking and trigger capabilities. This presentation covers the performance of the muon system, focusing on the stability of the established detectors over time, their ability to handle increasing luminosity and associated irradiation levels, and studies on detector aging. Emphasis will be placed on the NSW upgrade, including the strategies adopted for alignment, track reconstruction, and trigger. The performance results presented in this contribution are based on Run 3 data collected up to 2024.

Particles doi: 10.3390/particles9010023

Authors: Francesco Giovanni Celiberto

We examine the leading-power fragmentation of fully heavy pentaquarks in high-energy hadronic collisions. To this end, we complete the release of the hadron structure-oriented PQ5Q1.0 fragmentation functions by discussing the P5c set and delivering the P5b one. These functions incorporate an improved computation of the initial-scale input for the constituent heavy-quark fragmentation channel, making them particularly suitable for describing both the direct formation of a compact multicharm state and the hadronization from a diquark–antiquark–diquark configuration. For phenomenological applications, we employ the data-validated (sym)Jethad framework to compute and analyze NLL/NLO+ semi-inclusive production rates of pentaquark-plus-jet systems at the upcoming HL-LHC and the future FCC. This study marks a further step toward connecting hadronic structure, precision QCD, and the emerging physics of exotic matter.

Particles doi: 10.3390/particles9010022

Authors: Giorgio Almirante

The geometric contribution to superfluid density has been found to be of great importance in the inner crust of neutron stars. In this work we clarify how this contribution arises in the context of a band theory for neutrons. Specifically, we derive the dependence of the superfluid density on the magnitude of the pairing gap when the system has many bands cutting the Fermi energy, as is the case for neutrons in the inner crust. Also, in the perturbation theory framework, we find that it is essential to account for corrections to (Bogoliubov) quasi-particle states in order to obtain the geometric contribution. Accounting only for the corrections to (Hartree–Fock) single-particle states leads to the conventional contribution only.

Particles doi: 10.3390/particles9010021

Authors: Lorenzo Fortunato

Short-lived nuclear systems with light to medium masses are showing halo phenomena in regions of the nuclear chart that were still unexplored when halo nuclei were discovered 40 years ago. We study these exotic systems with three-body models, including nucleon–nucleon correlations, with the aim of reproducing measurable properties like radii and electromagnetic transition strengths. On the nucleon-rich side, drip-line fluorine isotopes are showing clear signs of a halo structure. Recently, we proposed that F29 is a moderate two-neutron halo nucleus with a large radius and a strong B(E1) response to the continuum. The three-body model places it at the borders of the island of inversion, which is corroborated by new data. According to our models, the next interesting isotope, F31, also has large spatial extension due to p-wave components and enhanced B(E1) response, pointing to a speculative halo structure. On the proton-rich side, we have studied the Sb102 system, composed of a Sn100 core plus a proton–neutron-correlated subsystem. We find that the weakening of the proton–neutron correlations with respect to the bare deuteron indicates that this is a one-proton emitter. We propose that the presence of a resonant state and its decay might provide a crucial benchmark for this system.

Particles doi: 10.3390/particles9010020

Authors: Leonardo Rodrigues Miguel Felizardo

Superheated liquid detectors (SLDs) exhibit strong sensitivity to fast neutrons and intrinsic insensitivity to gamma radiation, making them promising candidates for detecting shielded nuclear materials in security and non-proliferation applications. This work evaluates the feasibility of octafluoropropane-based superheated droplet detectors (SDDs) for identifying neutron-emitting materials concealed behind common attenuators. A combined acoustic and optical readout system was implemented, including a validated pulse-shape analysis method and a machine-learning-based bubble detection algorithm using YOLOv5. The optical system achieved a detection precision of approximately 80% within the defined region of interest. While the acoustic system remains the primary and more mature detection channel, the optical approach demonstrates feasibility but is not yet operationally ready for field deployment. Experiments with an AmBe neutron source and various shielding materials demonstrate that SDDs reliably detect fast neutrons under realistic inspection conditions while remaining insensitive to gamma radiation. These results support the feasibility of SLD-based systems as low-cost, passive tools for detecting shielded nuclear materials in field environments.

Particles doi: 10.3390/particles9010019

Authors: Giuseppe Osteria Johannes Eser Angela Olinto

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is a proposed dual-satellite mission to observe Ultra-High-Energy Cosmic Rays (UHECRs), increase the statistics at the highest energies, and observe Very-High-Energy Neutrinos (VHENs) following multi-messenger alerts of astrophysical transient events, such as gamma-ray bursts and gravitational wave events, throughout the universe. POEMMA–Balloon with radio (PBR) is a small-scale version of the POEMMA design, adapted to be flown as a payload on one of NASA’s suborbital Super Pressure Balloons (SPBs) circling over the Southern Ocean for more than 20 days after a launch from Wanaka, New Zealand. The main science objectives of PBR are: (1) to observe UHECRs via the fluorescence technique from suborbital space; (2) to observe horizontal high-altitude air showers (HAHAs) with energies above the cosmic ray knee (E > 3PeV) using optical and radio detection for the first time; and (3) to follow astrophysical event alerts in the search of VHENs. The PBR instrument consists of a 1.1 m aperture Schmidt telescope similar to the POEMMA design, with two cameras on its focal surface: a Fluorescence Camera (FC) and a Cherenkov Camera (CC). In addition, PBR has a Radio Instrument (RI) optimized for detecting EASs (covering the 60–660 Mhz range). The FC observes UHECR-induced EASs in the ultraviolet (UV) spectrum using an array of 9216-pixel Multi-Anode Photo-Multiplier Tubes (MAPMTs) imaged every 1 μs. The CC uses a 2048-pixel Silicon Photo-Multiplier (SiPM) imager to observe cosmic-ray-induced HAHAs and search for neutrino-induced upward-going EASs. The CC covers a spectral range of 320–900 nm, with an integration time of 10 ns. This contribution provides an overview of PBR instruments and their current status.

Particles doi: 10.3390/particles9010018

Authors: Zacharias Roupas

In this paper, we review our semi-analytic model of stellar black hole (BH) mass growth via gas accretion in gas-rich stellar clusters during their birthstage within the first ∼10Myr after the first stellar formation event. Such proto-stellar clusters are massive and compact, with typical masses ∼106M⊙ and sizes ∼1pc, as suggested by recent James Webb Space Telescope (JWST) observations. We find that by the end of the gas depletion process, BH masses are shifted to values within and above the BH mass gap, well within the range of components of the recent gravitational-wave (GW) signal GW231123, and up to masses ∼103M⊙.

Particles doi: 10.3390/particles9010017

Authors: Imene Benabdelghani Miklós Ákos Kedves Ádám Inger Márk Aladi

We present a systematic study on the optical response of plasma mirrors generated in polymer foils under ultrashort laser pulse irradiation within the non-relativistic intensity regime, reaching up to 2×1017 W/cm2. Using a Ti:sapphire system that delivers 50 fs pulses, we simultaneously measured reflection, transmission, and diffuse scattering with three energy meters for single-shot laser energies of 5, 10, 15, and 20 mJ as a function of the laser spot size on the target. The results reveal intensity-dependent variations in reflectivity, accompanied by simultaneous changes in transmission and scattering, allowing to estimate laser energy absorption by the polymer. Morphological analysis of the plasma surface suggests a significant role in modifying energy absorption, with implications for the efficiency of processes such as laser particle acceleration, nuclear fusion, and attosecond pulse generation. These findings provide critical insights into plasma mirror formation, absorption dynamics in polymers, and the potential of nanostructured polymer targets in high-intensity laser–matter interaction applications.

Particles doi: 10.3390/particles9010016

Authors: Andrea Di Salvo Emanuele Trossarello Micol Maria Bargelli Federico Reynaud Matteo Abrate Richard Wheadon Marco Mignone Angelo Rivetti Sara Garbolino Mario Edoardo Bertaina

This work describes the development of the Multi-channel Integrated Zone-sampling Analogue-memory based Readout (MIZAR) ASIC. This 64-channel chip was designed as part of NASA’s POEMMA Balloon with RADIO (PBR) mission, which aims to detect Ultra-High-Energy Cosmic Rays (UHECRs) and τ showers produced by the interaction of Cosmic Neutrinos (CNs) in the crust. The ASIC was implemented to read out a tile of 8 × 8 Silicon Photomultipliers (SiPMs) used to acquire the optical Cherenkov signals generated by Extensive Air Showers (EASs). A channel is partitioned into 256 cells where each one integrates an analogue memory, a Wilkinson Analog-to-Digital Converter (ADC) and a digital memory operating at the nominal sampling rate of 200 MS/s (with a 5 ns integration time). The signal is digitized on-chip, then the converted data is read out by an FPGA. The MIZAR also provides a 64-bit hitmap as a first-level trigger which can be elaborated by an external firmware. This ASIC can also be configured to further segment the channels into units of 32 or 64 cells each and the ADC resolution can be set to a range between 8 and 12 bits. The chip was designed in a commercial 65 nm CMOS technology node and it was submitted for production in December 2024. The ASICs were delivered in March 2025.

Particles doi: 10.3390/particles9010015

Authors: Konstantin M. Belotsky Maksim L. Solovev

In this work we test the possibility of accounting for the positron anomaly with annihilating dark matter particles without contradicting the gamma-ray constraints due to their unconventional space distribution. To achieve that, we consider two-component dark matter, whose major constituent is inert and forms the halo of the Galaxy, while the second, minor, component consists of annihilating particles that could form some different structure. This work is the next logical step after our previous “dark disk model” where an active DM component was considered to form a disk, allowing good suppression of accompanying gamma-radiation. Nowadays that model is not enough to avoid the contradiction, so we are testing a new, more complex one with a spiral spatial distribution like the one of baryons. We have previously tested two simplified toy models of ring-like density profiles and one simple spiral density profile that have shown good improvement compared to the disk case. In this work, we take things further and consider a more physically grounded density profile constructed on the base of a modern model of the baryon density of our Galaxy. Contrary to our expectations, this advanced model shows much worse agreement with the data than previous toy models.

Particles doi: 10.3390/particles9010014

Authors: Gaia De Palma Marco Cecca Leonardo Di Venere Francesco Licciulli Mario Nicola Mazziotta Elisabetta Bissaldi James Buckley Blake Bal Richard Bose Adrian Zink

The Advanced Particle–astrophysics Telescope (APT) is a mission concept for a future space-based MeV-TeV observatory, designed to combine a Compton and e+e− pair telescope, aiming to improve the sensitivity of the instruments to γ rays in the MeV-GeV range by at least one order of magnitude. To validate and study the technologies that will be employed on the observatory, a small-scale prototype, the Antarctic Demonstrator for APT (ADAPT), is currently being developed to fly on a balloon in Antarctica during the local 2026–2027 flight season. Among its subdetectors there is an Imaging CsI calorimeter (ICC), consisting of 4 layers of CsI(Na) crystals with crossed WLS fibers, coupled to Silicon Photomultipliers (SiPMs). A key element of the design is the multichannel front-end electronics, based on the SMART (SiPM Multichannel ASIC for high-Resolution Cherenkov Telescopes) ASIC, which combines compactness, cost-effectiveness, and a high level of integration. This work reports the results of quality-control tests performed on the custom readout boards for the ICC, and provides an overview of the present status of the mission.

Particles doi: 10.3390/particles9010013

Authors: Nathan Franel Vincent Tatischeff David Murphy Alexey Ulyanov Caimin McKenna Lorraine Hanlon Prerna Baranwal Christophe Beigbeder Arnaud Claret Ion Cojocari Nicolas de Séréville Nicolas Dosme Eric Doumayrou Mariya Georgieva Clarisse Hamadache Sally Hankache Jimmy Jeglot Mózsi Kiss Beng-Yun Ky Vincent Lafage Philippe Laurent Christine Le Galliard Joseph Mangan Aline Meuris Mark Pearce Jean Peyré Arjun Poitaya Diana Renaud Arnaud Saussac Varun Varun Matias Vecchio Colin Wade

COMCUBE-S (Compton Telescope CubeSat Swarm) is a proposed mission aimed at understanding the radiation mechanisms of ultra-relativistic jets from Gamma-Ray Bursts (GRBs). It consists of a swarm of 16U CubeSats carrying a state-of-the-art Compton polarimeter and a bismuth germanium oxide (BGO) spectrometer to perform timing, spectroscopic and polarimetric measurements of the prompt emission from GRBs. The mission is currently in a feasibility study phase (Phase A) with the European Space Agency to prepare an in-orbit demonstration. Here, we present the simulation work used to optimise the design and operational concept of the microsatellite constellation, as well as estimate the mission performance in terms of GRB detection rate and polarimetry. We used the MEGAlib software to simulate the response function of the gamma-ray instruments, together with a detailed model for the background particle and radiation fluxes in low-Earth orbit. We also developed a synthetic GRB population model to best estimate the detection rate. These simulations show that COMCUBE-S will detect about 2 GRBs per day, which is significantly higher than that of all past and current GRB missions. Furthermore, simulated performance for linear polarisation measurements shows that COMCUBE-S will be able to uniquely distinguish between competing models of the GRB prompt emission, thereby shedding new light on some of the most fundamental aspects of GRB physics.

Particles doi: 10.3390/particles9010012

Authors: Maxim Krasnov Valery Nikulin

We investigate primordial black hole (PBH) production via the collapse of supercritical domain walls in a quadratic f(R)-gravity model with tensor extensions. The effective field theory for an extra space’s scalar curvature provides a foundation for the formation of these dense walls. In our work, domain walls are found to be supercritical. Their properties were extensively studied in the literature, where it was demonstrated that they create wormholes and escape into baby universes through them. Closure of the wormhole leads to black hole creation, providing a mechanism for the production of primordial black holes in our model. We calculate the mass spectrum of such black holes and mass distribution within clusters of them. When accretion is accounted for, the black holes produced under this mechanism present viable dark matter candidates.

Particles doi: 10.3390/particles9010011

Authors: Andrea Addazi Giuseppe Meluccio

The microscopic origin of the de Sitter entropy remains a central puzzle in quantum gravity that is related to the cosmological constant problem. Within the paradigm of Holographic Naturalness, we propose that this entropy is carried by a vast number of light, coherent degrees of freedom—called “hairons”—which emerge as the moduli of gravitational instantons on orbifolds. Starting from the Euclidean de Sitter instanton (S4), we construct a new class of orbifold gravitational instantons, S4/ZN, where N corresponds to the de Sitter entropy. We demonstrate that the dimension of the moduli space of these instantons scales linearly with N, and we identify these moduli with the hairon fields. A ZN symmetry, derived from Wilson loops in the instanton background, ensures the distinguishability of these modes, leading to the correct entropy count. The hairons acquire a mass of the order of the Hubble scale and exhibit negligible mutual interactions, suggesting that the de Sitter vacuum is a coherent state, or Bose–Einstein condensate, of these fundamental excitations. Then, we present a novel framework which unifies neutrino mass generation with the cosmological constant through gravitational topology and holography. The small neutrino mass scale emerges naturally from first principles, without requiring new physics beyond the Standard Model and Gravity. The gravitational Chern–Simons structure and its anomaly with neutrinos force a topological Higgs mechanism, leading to neutrino condensation via S4/ZN gravitational instantons. The number of topological degrees of freedom N∼MP2/Λ∼10120 provides both the holographic counting of the de Sitter entropy and a 1/Ninformation see-saw mechanism for neutrino masses. Our framework makes the following predictions: (i) a neutrino superfluid condensation forming Cooper pairs below meV energies, as a viable candidate for cold dark matter; (ii) a possible resolution of the strong CP problem through a QCD composite axion state; (iii) time-varying neutrino masses which track the evolution of dark energy; and (iv) several distinctive signatures in astroparticle physics, ultra-high-energy cosmic rays and high magnetic field experiments.

Particles doi: 10.3390/particles9010010

Authors: Jindrich Jelinek Benedikt Bergmann Petr Smolyanskiy

This work presents a simulation study of a Timepix3 telescope composed of nine detectors for use as a Compton scatter polarimeter in the energy range of 35–100 keV. Four detectors carry 1 mm thick silicon (Si) sensors and five detectors carry 1 mm thick cadmium telluride (CdTe) sensors. The modulation factor for 100% linearly polarized X-ray beams was found to be μ100>70% in the energy range of 55–80 keV. The quality factor of the polarimeter has its maximum 12.8% at the energy 75 keV. The comparison of quality factors and the calculations of a hypothetical observation of the Crab nebula show that this multilayer Timepix3 approach is competitive with contemporary X-ray polarimeters.

Particles doi: 10.3390/particles9010009

Authors: David Maurin Fiorenza Donato Saverio Mariani

The interpretation of high-precision Galactic cosmic-ray data from AMS-02, CALET, DAMPE, etc., is fundamentally limited by nuclear cross-sections uncertainties. This proceeding highlights the results presented at the XSCRC2024 workshop, which aims at bringing together the cosmic-ray, nuclear, and particle physics communities, with the goal of improving cross-section measurements across various domains, from nuclei production for constraining cosmic-ray transport parameters, to antiproton and anti-deuteron production for dark matter searches. This workshop lead to a comprehensive roadmap for new cross-section measurements in the next decade, as well as other outcomes.

Particles doi: 10.3390/particles9010008

Authors: Nuha Felemban

Identified-hadron production (p, π±, K±) in π++Be at plab=60GeV/c (s≃10.6GeV) is investigated using Pythia 8.315 (Monash tune) with the Angantyr extension. Differential multiplicities d2n/(dpdθ) are confronted with NA61/SHINE measurements across standard θ bins. Within the fluctuating-radii Double-Strikman (DS) scheme, two unsuppressed opacity mappings are compared to quantify systematics. In addition, a minimal extension is introduced: a flat, post-classification, channel-wise acceptance applied after ND/SD/DD/EL tagging. It acts on primary and secondary πN pairs, keeps hadronization fixed (Lund string), and leaves the internal event generation of each admitted subcollision unchanged. Opacity-mapping variations alone induce only percent-level differences and do not resolve the soft/forward tensions. By contrast, the flat acceptance—interpretable as a reduced effective ND weight—improves agreement across species and angles. It hardens the forward π+ spectra and lowers large-θ yields, produces milder charge-asymmetric changes for π− consistent with the weaker leading feed, suppresses proton yields at all angles (with a residual ∼30% forward high-p deficit), and improves K±, with a stronger effect for K+ than K−. These results show that a geometry-blind reweighting of the subcollision mixture suffices to capture the main NA61/SHINE trends for π++Be at SPS energies without modifying hadronization. The approach provides a controlled baseline for subsequent, channel-balanced refinements and broader π+A tuning.

Particles doi: 10.3390/particles9010007

Authors: Smiriti Srivastava Evgeny Demenev Claudio Labanti Lorenzo Amati Riccardo Campana Giuseppe Baldazzi Edoardo Borciani Paolo Calabretto Francesco Ficorella Ezequiel J. Marchesini Giulia Mattioli Ajay Sharma David Novel Giancarlo Pepponi Enrico Virgilli

This paper presents the procedures employed for experimental functional and performance characterization of a 2 × 2 pixel prototype detection system tailored specifically for the X and Gamma-ray Imaging Spectrometer (XGIS) instrument onboard the THESEUS mission. The XGIS system comprises of two coded masked wide field cameras integrated with monolithic SDDs (Silicon Drift Detectors) and CsI:Tl (Thallium doped-Cesium Iodide) scintillators, contributing to its broad X and γ-ray detection range. Given the space instrumentation complexity, thorough requirement qualification and testing procedures are essential. This work focuses on working principle, the testing setup utilized, and observed performance for the small scale four-pixel XGIS prototype. Furthermore, the alignment of light output performance of the four-pixel SDD and scintillator prototype detection system with the XGIS instrument requirements is emphasized.

Particles doi: 10.3390/particles9010006

Authors: Simona Bartocci Roberto Battiston Stefania Beolè Franco Benotto Piero Cipollone Silvia Coli Andrea Contin Marco Cristoforetti Cinzia De Donato Cristian De Santis Andrea Di Luca Floarea Dumitrache Francesco Maria Follega Simone Garrafa Botta Giuseppe Gebbia Roberto Iuppa Alessandro Lega Mauro Lolli Giuseppe Masciantonio Matteo Mergè Marco Mese Riccardo Nicolaidis Francesco Nozzoli Alberto Oliva Giuseppe Osteria Francesco Palma Federico Palmonari Beatrice Panico Stefania Perciballi Francesco Perfetto Piergiorgio Picozza Michele Pozzato Marco Ricci Ester Ricci Sergio Bruno Ricciarini Zouleikha Sahnoun Umberto Savino Valentina Scotti Enrico Serra Alessandro Sotgiu Roberta Sparvoli Pietro Ubertini Veronica Vilona Simona Zoffoli Paolo Zuccon

The accurate simulation of sub-GeV particle detectors is essential for interpreting experimental data and optimizing detector design. This work identifies and addresses several critical aspects in modeling such detectors, taking as a case study the High-Energy Particle Detector (HEPD-02), a space-borne instrument developed within the CSES-02 mission to measure electrons in the ∼3–100 MeV range, protons and light nuclei in the ∼30–200 MeV/n. The HEPD-02 instrument consists of a silicon tracker, plastic and LYSO scintillator calorimeters, and anticoincidence systems, making it a representative example of a complex low-energy particle detector operating in Low Earth Orbit. Key challenges arise from replicating intricate detector geometries derived from CAD models, selecting appropriate hadronic physics lists for low-energy interactions, and accurately describing the detector response—particularly quenching effects in scintillators and digitization in solid-state tracking planes. Particular attention is given to three critical aspects: the precise CAD-level geometry implementation, the impact of hadronic physics models on the detector response, and the parameterization of scintillation quenching. In this study, we present original solutions to these challenges and provide data–MC comparisons using data from HEPD-02 beam tests.

Particles doi: 10.3390/particles9010005

Authors: Diego Julio Cirilo-Lombardo

The para-positronium system S01Ps is described by means of specially constructed coherent states (CSs) in the Klauder–Perelomov sense. It is analyzed from the physical point of view and from the geometry underlying the relevant symmetry group establishing the dynamics of the processes. In this new theoretical context, the possibility of a gamma-ray laser emission is investigated within a QFT context, showing explicitly that, in addition to the oscillator solution based only on a Bogoliubov approximation for the condensate, there is a second phase or “squeezed” stage by which physical features beyond the classical ones appear. Explicitly, while the generated photons are in the active medium (e.g., Ps-BEC), the evolution is described by a Heisenberg–Weyl coherent state with displacement operators dependent on the interaction time, which is related to the condensate shape. After the interaction time has elapsed, we explicitly demonstrate that the displacement operator of the S01Ps is transformed into a squeezed operator of the photonic fields modulated by the matrix element of the Positronium decay MS01Ps→2γ. We also show that this squeezed operator (belonging to the Metaplectic group) generates a non-classical radiation state spanning only even (s = 1/4) levels in the number of photons. The implications in astrophysical systems of interest, considering gamma-ray coherent emission and the possibility of an S01Ps−BEC in the context of pulsars, blazars, and quasars, are briefly discussed.

Particles doi: 10.3390/particles9010004

Authors: Nicolas De Angelis Abhay Kumar Sergio Fabiani Ettore Del Monte Enrico Costa Giovanni Lombardi Alda Rubini Paolo Soffitta Andrea Alimenti Riccardo Campana Mauro Centrone Giovanni De Cesare Sergio Di Cosimo Giuseppe Di Persio Alessandro Lacerenza Pasqualino Loffredo Gabriele Minervini Fabio Muleri Paolo Romano Emanuele Scalise Enrico Silva Davide Albanesi Ilaria Baffo Daniele Brienza Valerio Campomaggiore Giovanni Cucinella Andrea Curatolo Giulia de Iulis Andrea Del Re Vito Di Bari Simone Di Filippo Immacolata Donnarumma Pierluigi Fanelli Nicolas Gagliardi Paolo Leonetti Matteo Mergè Dario Modenini Andrea Negri Daniele Pecorella Massimo Perelli Alice Ponti Francesca Sbop Paolo Tortora Alessandro Turchi Valerio Vagelli Emanuele Zaccagnino Alessandro Zambardi Costantino Zazza

Our Sun is the closest X-ray astrophysical source to Earth. As such, it makes for a strong case study to better understand astrophysical processes. Solar flares are particularly interesting as they are linked to coronal mass ejections as well as magnetic field reconnection sites in the solar atmosphere. Flares can therefore provide insightful information on the physical processes at play on their production sites but also on the emission and acceleration of energetic charged particles towards our planet, making it an excellent forecasting tool for space weather. While solar flares are critical to understanding magnetic reconnection and particle acceleration, their hard X-ray polarization—key to distinguishing between competing theoretical models—remains poorly constrained by existing observations. To address this, we present the CUbesat Solar Polarimeter (CUSP), a mission under development to perform solar flare polarimetry in the 25–100 keV energy range. CUSP consists of a 6U-XL platform hosting a dual-phase Compton polarimeter. The polarimeter is made of a central assembly of four 4 × 4 arrays of plastic scintillators, each coupled to multi-anode photomultiplier tubes, surrounded by four strips of eight elongated GAGG scintillator bars coupled to avalanche photodiodes. Both types of sensors from Hamamatsu are, respectively, read out by the MAROC-3A and SKIROC-2A ASICs from Weeroc. In this manuscript, we present the preliminary spectral performances of single plastic and GAGG channels measured in a laboratory using development boards of the ASICs foreseen for the flight model.

Particles doi: 10.3390/particles9010003

Authors: Giulia Mattioli Claudio Labanti Enrico Virgilli Lorenzo Amati Riccardo Campana Giuseppe Baldazzi Smiriti Srivastava Edoardo Borciani Paolo Calabretto Ezequiel J. Marchesini Ajay Sharma Evgeny Demenev Francesco Ficorella David Novel Giancarlo Pepponi Giovanni La Rosa Paolo Nogara Giuseppe Sottile

Gamma-Ray Bursts (GRBs) are intense bursts of high-energy photons which, in just a few seconds, outshine all other γ-ray emitters in the sky. Due to their extreme luminosity, GRBs are not only important as high-energy astrophysical phenomena but also serve as valuable probe models of the far, high-redshift Universe. The importance of these events has pushed the High-Energy Astrophysics community to propose new mission concepts over the past decade, prompting dedicated research and development efforts to achieve the required technological readiness levels. The X and Gamma-Ray Imager and Spectrometer (XGIS) is one of the two GRB monitors onboard the proposed, upcoming THESEUS space mission. Building on strong heritage from previous studies, ongoing developments and optimizations are focused on enhancing the instrument’s capabilities and increasing its technological maturity. This work presents the current status of the XGIS instrument and the latest technological advancements achieved in preparation for its deployment on THESEUS.

Particles doi: 10.3390/particles9010002

Authors: Paolo Soffitta Enrico Costa Ettore Del Monte Alessandro Di Marco Sergio Fabiani Riccardo Ferrazzoli Fabio La Monaca Fabio Muleri Alda Rubini Alessio Trois

This paper discusses issues encountered during the early development of the instrument on the Imaging X-ray Polarimetry Explorer (IXPE), a NASA–ASI Small Explorer mission launched on 9 December 2021. IXPE has observed about 100 sources, yielding meaningful polarimetry for most of them. An on-board calibration system mitigated most non-ideal detector behaviors during operations. Data from the on-board polarized and unpolarized X-ray sources are routinely ingested by the flight pipeline to correct the instrument response in a manner transparent to users. Based on its scientific return and payload health, the IXPE mission has been extended through 2028. The lessons learned are informing the design of next-generation X-ray polarimetry missions, as discussed elsewhere in these conferences.

Particles doi: 10.3390/particles9010001

Authors: Yide Wei Hui Wang

The hadron calorimeter is a central component of the CMS detector, vital for measuring hadron energies and reconstructing missing transverse momentum. This paper reviews its performance before and after the Phase 1 upgrade (completed in 2019), which upgraded both back-end and front-end electronics, including photodetectors and charge-integrating ADC with precise-timing TDC, as well as its depth segmentation in the barrel and endcaps. This paper describes energy reconstruction algorithms that suppress out-of-time signals, along with high-precision timing alignment and multi-step energy calibration procedures to mitigate radiation damage and improve energy resolution Performance evaluations using proton–proton collision data demonstrate that the upgraded detector and reconstruction techniques achieve good resolution and robust operation under high-luminosity conditions.

Particles doi: 10.3390/particles8040104

Authors: Konstantin Zsukovszki Istvan Papp

Laser-driven ion acceleration in dense, hydrogen-rich media can be significantly enhanced by embedding metallic nanoantennas that support localized surface plasmon (LSP) resonances. Using large-scale particle-in-cell (PIC) simulations with the EPOCH code, we investigate how nanoantenna geometry and laser pulse parameters influence proton acceleration in gold-doped polymer targets. The study covers dipole, crossed, and advanced 3D-cross antenna configurations under laser intensities of 1017–1019 W/cm2 and pulse durations from 2.5 to 500 fs, corresponding to experimental conditions at the ELI laser facility. Results show that the dipole antennas exhibit resonance-limited proton energies of ~0.12 MeV, with optimal acceleration at the intensities 4 × 1017–1 × 1018 W/cm2 and pulse durations around 100–150 fs. This energy is higher by roughly three orders of magnitude than the proton energy for the same field and same polymer without dopes: ~1–2 × 10−4 MeV. Crossed antennas achieve higher energies (~0.2 MeV) due to dual-mode plasmonic coupling that sustains local fields longer. Advanced 3D and Yagi-like geometries further enhance field localization, yielding proton energies up to 0.4 MeV and larger high-energy proton populations. For dipole antennas, experimental data from ELI exists and our results agree with it. We find that moderate pulses preserve plasmonic resonance for longer and improve energy transfer efficiency, while overly intense pulses disrupt the resonance early. These findings reveal that plasmonic field enhancement and its lifetime govern energy transfer efficiency in laser–matter interaction. Crossed and 3D geometries with optimized spacing enable multimode resonance and sequential proton acceleration, overcoming the saturation limitations of simple dipoles. The results establish clear design principles for tailoring nanoantenna geometry and pulse characteristics to optimize compact, high-energy proton sources for inertial confinement fusion and high-energy-density applications.

Particles doi: 10.3390/particles8040103

Authors: Pei-Pin Yang Abd Haj Ismail

The blast-wave model with Boltzmann–Gibbs statistics is used to examine the transverse momentum spectra of K∗0 mesons generated at the Relativistic High-Energy Collider (RHIC) Beam Energies with mid-rapidity (|y|<1) in symmetric Au−Au collisions. There is a clear correlation between the extracted kinetic freeze-out temperature (T0) and transverse flow velocity (βT) in various collision centralities and center-of-mass energies (sNN). Since a larger initial energy density delays freeze-out and a shorter system lifetime limits cooling, T0 is directly proportional to both sNN and peripheral collisions. On the other hand, βT drops in peripheral symmetric collisions due to weaker collective expansion, while it rises with sNN because of larger pressure gradients. The concurrence between the thermal and collective energy components in the expanding fireball is reflected in the obvious anti-correlation between T0 and βT. These findings support hydrodynamic predictions and offer important new information about QGP’s freeze-out behavior.

Particles doi: 10.3390/particles8040102

Authors: Andrea Bulgarelli Luca Castaldini Nicolò Parmiggiani Ambra Di Piano Riccardo Falco Alessio Aboudan Lorenzo Amati Andrea Argan Paolo Calabretto Mauro Dadina Adriano De Rosa Valentina Fioretti Claudio Labanti Giulia Mattioli Gabriele Panebianco Carlotta Pittori Alessandro Rizzo Smiriti Srivastava Enrico Virgilli

Next-generation space observatories for high-energy gamma-ray astrophysics will increase scientific return using onboard machine learning (ML). This is now possible thanks to today’s low-power, radiation-tolerant processors and artificial intelligence accelerators. This paper provides an overview of current and future ML applications in gamma-ray space missions focused on high-energy transient phenomena. We discuss onboard ML use cases that will be implemented in the future, including real-time event detection and classification (e.g., gamma-ray bursts), and autonomous decision-making, such as rapid repointing to transient events or optimising instrument configuration based on the scientific target or environmental conditions.

Particles doi: 10.3390/particles8040101

Authors: Oscar Adriani Lucia Baldesi Eugenio Berti Pietro Betti Massimo Bongi Alberto Camaiani Massimo Chiari Raffaello D’Alessandro Giacomo De Giorgi Noemi Finetti Leonardo Forcieri Elena Gensini Andrea Paccagnella Lorenzo Pacini Paolo Papini Oleksandr Starodubtsev Anna Vinattieri Chiara Volpato

The study of the antimatter component in cosmic rays is essential for the understanding of their acceleration and propagation mechanisms, and is one of the most powerful tools for the indirect search of dark matter. Current methods rely on magnetic spectrometers for charge-sign discrimination, but these are not suitable for extending measurements to the TeV region within a short timeframe of a few decades. Since most of present and upcoming high-energy space experiments use large calorimeters, it is crucial to develop an alternative charge-sign discrimination technique that can be integrated with them. The Electron/Positron Space Instrument (EPSI) project, a two-year R&D initiative launched in 2023 with EU recovery funds, aims to address this challenge. The basic idea is to exploit the synchrotron radiation emitted by charged particles moving through Earth’s magnetic field. The simultaneous detection of an electron/positron with an electromagnetic calorimeter and synchrotron photons with an X-ray detector is enough to discriminate between the two particles at the event level. The main challenge is to develop an X-ray detector with a very large active area, high X-ray detection efficiency, and a low-energy detection threshold, compliant with space applications. In this paper, we give an overview of the EPSI project, with a focus on the general idea of the detection principle, the concept of the space instrument, and the design of the X-ray detector.

Particles doi: 10.3390/particles8040100

Authors: Peter S. Shternin

We reconsider the problem of neutrino-pair bremsstrahlung emission originating from the electromagnetic collisions of charged particles in nucleonic (npeμ) neutron star cores. Two limiting cases are considered: (i) protons in the normal state and (ii) protons in the superconducting state. In both cases, the dominant contribution to the bremsstrahlung emissivity QBrem comes from the transverse part of in-medium electromagnetic interactions. For non-superconducting matter, we obtain an unusual QBrem∝T23/3 temperature dependence due to the dynamical character of plasma screening in the transverse channel, but these are considerably smaller values of QBrem than in previous studies, rendering the considered process unimportant in practice. In contrast, for superconducting and superfluid matter, the neutrino emission processes involving nucleons are suppressed and QBrem due to lepton collisions provides the residual contribution to the neutrino emissivity of neutron star core matter. In the superconducting case, the plasma screening becomes static and the standard QBrem∝T8 temperature scaling is restored. Simple analytical expressions for QBrem in both limiting cases are provided.

Particles doi: 10.3390/particles8040099

Authors: Federica Cuna Maria Bossa Fabio Gargano Mario Nicola Mazziotta

The application of advanced Artificial Intelligence (AI) techniques in astroparticle experiments represents a major advancement in both data analysis and experimental design. As space missions become increasingly complex, integrating AI tools is essential for optimizing system performance and maximizing scientific return. This study explores the use of Graph Neural Networks (GNNs) within the tracking systems of space-based experiments. A key challenge in track reconstruction is the high level of noise, primarily due to backscattering tracks, which can obscure the identification of primary particle trajectories. We propose a novel GNN-based approach for node-level classification tasks, specifically designed to distinguish primary tracks from backscattered ones within the tracker. In this framework, AI is employed as a powerful tool for pattern recognition, enabling the system to identify meaningful structures within complex tracking data and to discriminate signal from backscattering with higher precision. By addressing these challenges, our work aims to enhance the accuracy and reliability of data interpretation in astroparticle physics through the advanced deep learning techniques.

Particles doi: 10.3390/particles8040098

Authors: Kiwan Park

We investigate the α and β effects in a rotating spherical plasma system relevant to astrophysical contexts. In particular, we focus on how kinetic and magnetic (current) helicities influence the magnetic diffusivity β. These coefficients were modeled using three complementary theoretical approaches. Direct numerical simulation (DNS) data (large-scale magnetic field B¯, turbulent velocity u, and turbulent magnetic field b) were then used to obtain the actual values of αEM−HM, βEM−HM, βvv−vw, and βbb+jb. Using these coefficients, we reconstructed B¯ and compared it with the DNS results. In the kinematic regime, where B¯ remains weak, all models agree well with DNS. In the nonlinear regime, however, the field reconstructed with βvv−vw alone deviates from DNS and grows without bound. Incorporating the turbulent magnetic diffusion term βbb+jb suppresses this unphysical growth and restores consistency. Specifically, B¯DNS saturates at approximately 0.23 in the nonlinear regime. The reconstructed B¯ using βEM−HM saturates at B¯∼0.3. When βvv−vw+bb+jb(=βvv−vw+βbb+jb) is used, B¯ varies from about 0.3 to 0.23. These results indicate that kinetic helicity reduces β (or provides a negative contribution), thereby amplifying B¯, whereas turbulent current helicity, together with turbulent magnetic and kinetic energies, enhances β, thus suppressing B¯ in the nonlinear regime. In this respect, the new form of β differs from the conventional one, which acts solely to diffuse the magnetic field.

Particles doi: 10.3390/particles8040097

Authors: Riccardo Nicolaidis Andrea Abba Domenico Borrelli Adriano Di Giovanni Luigi Ferrentino Giovanni Franchi Francesco Nozzoli Giancarlo Pepponi Lorenzo Perillo David Schledewitz Enrico Verroi

NUSES is a planned space mission aiming to test new observational and technological approaches related to the study of low-energy cosmic rays, gamma rays, and high-energy astrophysical neutrinos. Two scientific payloads will be hosted onboard the NUSES space mission: Terzina and Zirè. Terzina will be an optical telescope readout by SiPM arrays for the detection and study of Cerenkov light emitted by Extensive Air Showers (EASs) generated by high-energy cosmic rays and neutrinos in the atmosphere. Zirè will focus on the detection of protons and electrons up to a few hundred MeV and 0.1–30 MeV photons and will include the Low-Energy Module (LEM). The LEM will be a particle spectrometer devoted to the observation of fluxes of low-energy electrons in the 0.1–7-MeV range and protons in the 3–50 MeV range in low Earth orbit (LEO) followed by the hosting platform. The detection of Particle Bursts (PBs) in this physics channel of interest could provide insights into understanding complex phenomena such as possible correlations between seismic events or volcanic activity with the collective motion of particles in the plasma populating Van Allen belts. With its compact size and limited acceptance, the LEM will allow the exploration of hostile environments such as the South Atlantic Anomaly (SAA) and the inner Van Allen belt, in which the anticipated electron fluxes are on the order of 106 to 107 electrons per square centimeter per steradian per second. Concerning the vast literature on space-based particle spectrometers, the innovative aspect of the LEM resides in its compactness, within 10×10×10 cm3, and in its “active collimation” approach to dealing with the problem of multiple scattering at these low energies. In this work, the geometry of the detector, its detection concept, its operation modes, and the hardware adopted will be presented. Some preliminary results from a Monte Carlo simulation (Geant4) will be shown.

Particles doi: 10.3390/particles8040096

Authors: Isaac Buckland Riccardo Munini Valentina Scotti

Future space detectors for Ultra High Energy neutrinos and cosmic rays will utilize Cherenkov telescopes to detect forward-beamed Cherenkov light produced by charged particles in Extensive Air Showers (EASs). A Cherenkov detector can be equipped with an array of Silicon Photo-Multiplier (SiPM) pixels, which offer several advantages over traditional Photo-Multiplier Tubes (PMTs). SiPMs are compact and lightweight and operate at lower voltages, making them well-suited for space-based experiments. The SiSMUV (SiPM-based Space Monitor for UV-light) is developing a SiPM-based Cherenkov camera for PBR (POEMMA Baloon with Radio) at INFN Napoli. To understand the response of such an instrument, a comprehensive simulation of the response of individual SiPM pixels to incident light is needed. For the accurate simulation of a threshold trigger, this simulation must reproduce the current produced by a SiPM pixel as a function of time. Since a SiPM pixel is made of many individual Avalanche Photo-Diodes (APDs), saturation and pileup in APDs must also be simulated. A Gaussian mixture fit to ADC count spectrum of a SiPM pixel exposed to low levels of laser light at INFN Napoli shows a significant amount of samples between the expected PE (Photo Electron) peaks. Thus, noise sources such as dark counts and afterpulses, which result in partially integrated APD pulses, must be accounted for. With static, reasonable values for noise rates, the simulation chain presented in this work uses the characteristics of individual APDs to produce the aggregate current produced by a SiPM pixel. When many such pulses are simulated and integrated, the ADC spectra generated by low levels of laser light at the INFN Napoli SiSMUV test setup can be accurately reproduced.

Particles doi: 10.3390/particles8040095

Authors: Sergei V. Chekanov Håkan Kjellerstrand

This paper presents a method for uncovering hidden analytic relationships among the fundamental parameters of the Standard Model (SM), a foundational theory in physics that describes the fundamental particles and their interactions, using symbolic regression and genetic programming. Using this approach, we identify the simplest analytic relationships connecting pairs of these constants and report several notable expressions obtained with relative precision better than 1%. These results may serve as valuable inputs for model builders and artificial intelligence methods aimed at uncovering hidden patterns among the SM constants, or potentially used as building blocks for a deeper underlying law that connects all parameters of the SM through a small set of fundamental constants.

Particles doi: 10.3390/particles8040094

Authors: Mario Nicola Mazziotta Liliana Congedo Giuseppe De Robertis Mario Giliberti Francesco Licciulli Antonio Liguori Leonarda Lorusso Nicola Nicassio Giuliana Panzarini Roberta Pillera

In this work, we present a novel compact particle identification (PID) detector concept based on Silicon Photomultipliers (SiPMs) optimized to perform combined Ring-Imaging Cherenkov (RICH) and Time-of-Flight (TOF) measurements using a common photodetector layer. The system consists of a Cherenkov radiator layer separated from a photosensitive surface equipped with SiPMs by an expansion gap. A thin glass slab, acting as a second Cherenkov radiator, is coupled to the SiPMs to perform Cherenkov-based charged particle timing measurements. We assembled a small-scale prototype instrumented with various Hamamatsu SiPM array sensors with pixel pitches ranging from 2 to 3 mm and coupled with 1 mm thick fused silica window. The RICH radiator consisted of a 2 cm thick aerogel tile with a refractive index of 1.03 at 400 nm. The prototype was successfully tested in beam test campaigns at the CERN PS T10 beam line with pions and protons. We measured a single-hit angular resolution of about 4 mrad at the Cherenkov angle saturation value and a time resolution better than 50 ps RMS for charged particles with Z = 1. The present technology makes the proposed SiPM-based PID system particularly attractive for space applications due to the limited detector volumes available. In this work, we present beam test results obtained with the detector prototype and we discuss possible configurations optimized for the identification of ions in space applications.

Particles doi: 10.3390/particles8040093

Authors: Felicia Carla Tiziana Barbato Ivan De Mitri Giuseppe De Robertis Adriano Di Giovanni Leonardo Di Venere Giulio Fontanella Fabio Gargano Mario Giliberti Francesco Licciulli Antonio Liguori Francesco Loparco Leonarda Lorusso Mario Nicola Mazziotta Giuliana Panzarini Roberta Pillera Pierpaolo Savina Aleksei Smirnov

NUSES is a pathfinder satellite that will be deployed in a low Earth orbit, designed with new technologies for space-based detectors. Ziré is one of the payloads of NUSES and aims to measure the spectra of electrons, protons, and light nuclei in a kinetic energy range spanning from a few MeVs to several hundred MeVs, as well as photons in the energy range from 0.1 MeV to 30 MeV. Ziré consists of a Fiber TracKer (FTK), a Plastic Scintillator Tower (PST), a calorimeter (CALOg), an AntiCoincidence System (ACS) and a Low Energy Module (LEM). The FTK is based on thin scintillating fibers read out by Silicon Photomultiplier (SiPM) arrays. We assembled a prototype of Ziré (Zirettino) equipped with a single FTK layer, a reduced number of PST layers and a partially instrumented CALOg. A preliminary version of the Ziré custom Front-End Board (FEB) featuring the on-the-shelf ASIC CITIROC by OMEGA/Weeroc was used for the readout. We carried out several beam test campaigns at CERN’s PS facility and a dynamic qualification test. The performance of FTK will be presented and discussed.

Particles doi: 10.3390/particles8040092

Authors: Valentina Scotti Giuseppe Osteria Marco Mese Antonio Anastasio Alfonso Boiano Isaac Buckland Vincenzo Masone Riccardo Munini Beatrice Panico Haroon Akhtar Qureshi

The study of Ultra-High-Energy Cosmic Rays is made possible by space telescopes that allow for the recording of signals generated by Extensive Air Showers (EAS) on the night side of the Earth’s atmosphere. One of the requirements for these telescopes is the detection of very low photon fluxes, achievable using the latest generation SiPMs characterized by high intrinsic gains, low power consumption, low weight, and robustness against accidental exposure to light. Despite these advantages, some technological issues still need to be addressed, such as the radiation hardness for operation in space. Therefore, the design of a SiPM-based focal surface for UHECR detection must consider the space qualification of SiPM arrays, with the development of compact arrays optimized for low dead-area focal surfaces. SiSMUV (SiPM-based Space Monitor for UV light) is a project dedicated to developing a compact and modular UV detector for use in space telescopes designed to study the fluorescence and Cherenkov signals produced by Ultra-High-Energy Cosmic Rays (UHECRs). Each SiSMUV module incorporates a matrix of SiPMs, a readout ASIC (Radioroc by Weeroc), and an FPGA into a monolithic block. This design enables the acquisition and processing of signals from the sensors. The system can connect to a PC for standalone operation or with back-end electronics for integration into more complex systems. In this paper, we will describe the prototype electronics, the experimental setup and the measurements performed to obtain parameters such as the gain of the SiPMs, and their photon detection efficiency (PDE). We will also present the firmware developed to interface with the readout ASIC and to transmit data to other peripherals.

Particles doi: 10.3390/particles8040091

Authors: Paolo Calabretto Claudio Labanti Enrico Virgilli Lorenzo Amati Riccardo Campana Giulia Mattioli Smiriti Srivastava Ezequiel J. Marchesini Edoardo Borciani Ajay Sharma Giovanni La Rosa Paolo Nogara Giuseppe Sottile Alfonso Pisapia

The X and Gamma Imager and Spectrometer (XGIS) on board THESEUS is a finely pixelized and modular instrument designed for broadband high-energy transient detection. XGIS consists of two cameras, each composed of 10 supermodules, with each supermodule further divided into 10 modules and each module made with 64 independent readout pixels based on Silicon Drift Detectors coupled with 5 × 5 × 30 mm3 CsI scintillator bars. An algorithm to quickly read out the signals from the 64 pixels and send them in chronological order through the module and supermodule logic up to the camera logic is under development. Furthermore, a challenge for space-based high-energy instruments is distinguishing X-/gamma-ray photons while effectively rejecting background photons and particles, including electrons, protons, and heavier cosmic rays. Unlike traditional systems that rely on anticoincidence systems, XGIS aims to achieve background rejection through an innovative readout logic that analyzes the spatial and temporal properties of energy deposits in the detector. By leveraging the finely pixelized structure, the readout system can differentiate single-photon events from charged-particle tracks based on energy deposition patterns and event topology.

Particles doi: 10.3390/particles8040090

Authors: Beatrice Panico Roberto Ammendola Antonio Anastasio Davide Badoni Mario Bertaina Francesco Cafagna Donatella Campana Marco Casolino Cristian De Santis Andrea Di Salvo Raffaele Gargiulo Alessandro Marcelli Laura Marcelli Vincenzo Masone Marco Mese Marco Mignone Giuseppe Osteria Giuseppe Passeggio Francesco Perfetto Haroon Akhtar Qureshi Enzo Reali Ester Ricci Valentina Scotti

POEMMA-Balloon with Radio (PBR) is designed as a payload for a NASA suborbital Super Pressure Balloon that will circle over the Southern Ocean and a mission duration as long as 50 days. The PBR instrument consists of a 1.1 m aperture Schmidt telescope similar to the POEMMA design with two cameras in its focal surface: a Fluorescence Camera (FC) and a Cherenkov Camera (CC). The CC camera is mainly devoted to the observation of cosmic-ray-induced high-altitude horizontal air showers (HAHAs) and search for neutrino-induced upward-going EAS. It will be made of 2048 SiPMs with a surface of 3 × 3 mm2 and a FoV of 12° by 6°, covering a spectral range of 320–900 nm. The CC camera is an innovative detector currently under construction. In this paper, information about its current status will be given.

Particles doi: 10.3390/particles8040089

Authors: Luca Ghislotti Paolo Lazzaroni Massimo Manghisoni Elisa Riceputi

The General AntiParticle Spectrometer is a balloon-borne experiment designed to search for low-energy cosmic-ray antinuclei as a potential indirect signature of dark matter. Over the course of at least three long-duration flights over Antarctica, it will explore the sub-250 MeV/n energy range with sensitivity to antideuterons and antihelium, while also extending antiproton measurements below 100 MeV. The instrument features a tracker built from more than one thousand lithium-drifted silicon detectors, each read out by a dedicated custom integrated circuit. With the first flight scheduled for the austral summer of 2025, a new prototype chip, ANTARES4, has been developed using a commercial 65 nm complementary metal-oxide semiconductor process for use in the second flight. It integrates eight independent analog channels, each incorporating a low-noise charge-sensitive amplifier with dynamic signal compression, a CR–RC shaping stage with eight selectable peaking times, and on-chip calibration circuitry. The charge-sensitive amplifier uses metal-oxide semiconductor feedback elements with voltage-dependent capacitance to support the wide input energy range from 10 keV to 100 MeV. Four alternative feedback implementations are included to compare performance and design trade-offs. Leakage current compensation up to 200 nA per detector strip is provided by a Krummenacher current–feedback network. This paper presents the design and architecture of ANTARES4, highlighting the motivations, design drivers, and performance requirements that guided its development.

Particles doi: 10.3390/particles8040088

Authors: José A. Barajas-Aguilar Francisco V. Flores-Baez José R. Morones-Ibarra

In this work, we calculate the Branching Ratio (BR) of the process ρ0→π0π0γ at tree level within the theoretical framework of with resonances, including the odd intrinsic parity sector. Owing to the nature of an effective field theory, the BR depends on three unknown couplings of the model: d4 and the combination c57=c5+c7. To constrain these unknown couplings, we use the experimental BR of this decay and explore the possibility of reducing the number of unknown couplings through the on-shell condition at one vertex. Our result suggests that off-shell conditions must be applied to both vertices, leading to a space parameter for the pair (c57,d4).

Particles doi: 10.3390/particles8040087

Authors: Maria Bossa Federica Cuna Fabio Gargano

Artificial intelligence has made remarkable progress across numerous domains, including physics, where machine learning and deep learning methods have become increasingly common. In high-energy physics, these approaches have significantly advanced tasks like event reconstruction, pattern recognition, and large-scale data analysis. The present study explores the application of machine learning techniques to the classification of electromagnetic and hadronic showers in space calorimeter experiments. Leveraging Monte Carlo simulations and a dedicated feature engineering, the findings demonstrate the strong potential of AI to improve classification performance in space calorimetry.

Particles doi: 10.3390/particles8040086

Authors: Pier Simone Marrocchesi

The MoonRay project is carrying out a concept study of a permanent lunar cosmic-ray (CR) and gamma-ray observatory, in view of the implementation of habitats on our satellite. The idea is to build a modular telescope that will be able to overcome the limitations, in available power and weight, of the present generation of CR instruments in Low Earth Orbit, while carrying out high-energy gamma-ray observations from a vantage point at the South Pole of the Moon. An array of fully independent modules (towers), with limited individual size and mass, can provide an acceptance more than one order of magnitude larger than instruments in flight at present. The modular telescope is designed to be deployed progressively, during a series of lunar missions, while collecting meaningful scientific data at the intermediate stages of its implementation. The operational power will be made available by the facilities maintaining the lunar habitats. With a geometric factor close to 15 m2sr and about 8 times larger sensitive area than FERMI-LAT, MoonRay will be able to carry out a very rich observational program over a time span of a few decades with an energy reach of 10 PeV allowing the exploration of the CR “knee” and the observation of the Southern Sky with gamma rays well into the TeV scale. Each tower (of approximate size 20 cm × 20 cm ×100 cm) is equipped with three instruments. A combined Charge and Time-of-Flight detector (CD-ToF) can identify individual cosmic elements, leveraging on an innovative two-layered array of pixelated Low-Gain Avalanche Diode (LGAD) sensors, with sub-ns time resolution. The latter can achieve an unprecedented rejection power against backscattered radiation from the calorimeter. It is followed by a tracker, providing also photon conversion, and by a thick crystal calorimeter (55 radiation lengths, 3 proton interaction lengths at normal incidence) with an energy resolution of 30–40% (1–2%) for protons (electrons) and a proton/electron rejection in excess of 105. A time resolution close to 100 ps has been obtained, with prototypal arrays of 3 mm × 3 mm LGAD pixels, in a recent test campaign carried out at CERN with Pb beam fragments.

Particles doi: 10.3390/particles8040085

Authors: Jin-Li Zhang

We investigate the off-shell generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs) of kaons within the framework of the Nambu–Jona-Lasinio model, employing proper time regularization. Compared to the pion case, the off-shell effects in kaons are of similar magnitude, modifying the GPDs by about 10–25%, which is notable. The absence of crossing symmetry leads to odd powers in the x-moments of the off-shell GPDs, giving rise to new off-shell form factors. We analyze the relations among these kaon off-shell form factors by analogy with electromagnetic form factors. Our results extend the off-shell GPDs from pions to kaons and simultaneously address the associated off-shell form factors. We also compare the off-shell and on-shell gravitational form factors of the kaon. In addition, the off-shell kaon TMD shows a stronger dependence on the momentum fraction x than its on-shell counterpart.

Particles doi: 10.3390/particles8040084

Authors: Alan A. Dzhioev Andrey V. Yudin Natalia V. Dunina-Barkovskaya Andrey I. Vdovin

Reliable predictions of (anti)neutrino spectra and luminosities are essential for assessing the feasibility of detecting pre-supernova neutrinos. Using the stellar evolution code MESA, we calculate the (anti)neutrino spectra and luminosities under realistic conditions of temperature, density, and electron fraction. Our study includes (anti)neutrinos produced by both thermal processes and nuclear weak-interaction reactions. By comparing the results of the thermal quasiparticle random-phase approximation with the standard technique based on the effective Q-value method, we investigate how thermal effects influence the spectra and luminosities of emitted (anti)neutrinos. Our findings show that a thermodynamically consistent treatment of Gamow–Teller transitions in hot nuclei enhances both the energy luminosity and the average energies of the emitted (anti)neutrinos.

Particles doi: 10.3390/particles8040083

Authors: Xinmei Zhu Hongxia Huang Jialun Ping

To investigate diquark correlation in baryons, the baryon spectra with different light–heavy quark combinations are calculated using Gaussian expansion method within both the naive quark model and the chiral quark model. By computing the diquark energies and separations between any two quarks in baryons, we analyze the diquark effect in the ud-q/Q, us-Q, ss-q/Q, and QQ-q/Q systems (where q=u,d, or s; Q=c,b). The results show that diquark correlations exist in baryons. In particular, for qq-Q and QQ-q systems, the same type of diquark exhibits nearly identical energy and size across different baryons. In the orbital ground states of baryons, scalar–isoscalar diquarks have lower energy and a smaller size compared to vector–isovector diquark, which qualifies them as “good diquarks”. In QQ-q systems, a larger mass of Q leads to a smaller diquark separation and a more pronounced diquark effect. In qq-Q systems, the separation between the two light quarks remains larger than that between a light and a heavy quark, indicating that the internal structure of such diquarks must be taken into account. A comparison between the naive quark model and the chiral quark model reveals that the introduction of meson exchange slightly increases the diquark size in most systems.

Particles doi: 10.3390/particles8040082

Authors: Francesco Dimiccoli Francesco Maria Follega Luigi Ernesto Ghezzer Roberto Iuppa Alessandro Lega Riccardo Nicolaidis Francesco Nozzoli Ester Ricci Enrico Verroi Paolo Zuccon

Lutetium–Yttrium Oxyorthosilicate (LYSO) crystals and EJ-200 plastic scintillators are widely recognized fast scintillating materials, valued for their high light yield and mechanical robustness, which make them well suited for demanding applications in high-energy physics and space research. Their non-proportional light response, along with their non-linear behavior at low-energy X-rays, has been extensively investigated in previous studies, revealing potential systematic effects in existing measurements. In this work, light quenching in both scintillators is measured under charged-particle excitation. The results are interpreted using the modified Birks–Onsager model, which provides a theoretical framework for understanding the underlying quenching mechanisms, as well as a generalized logistic parametrization, offering experimentalists a useful tool to characterize the detector’s light yield and associated uncertainties.

Particles doi: 10.3390/particles8030081

Authors: Zhuang Bi Kotaro Tanaka Heishun Zen Hideaki Ohgaki

To enable the single-shot measurement of extraction efficiency, a key parameter of an FEL oscillator, we developed an array-type secondary electron emission monitor capable of measuring the temporal evolution of the electron beam energy distribution in a macro-pulse at KU-FEL. The monitor consists of 24 ribbon-shaped electrodes and 2 shielding electrodes, and it is positioned after the energy analyzer magnet and just before a beam dump. The beam energy evolutions in a macro-pulse with and without FEL lasing were measured in a single shot with approximately 100 ns temporal resolution. From the results obtained, the extraction efficiency of FEL oscillators can be evaluated.

Particles doi: 10.3390/particles8030080

Authors: Warissara Tangyotkhajorn Thongchai Leetha Supachai Prawanta Prapaiwan Sunwong

During the detailed design of magnets for the storage ring of Siam Photon Source II (SPS-II), the influence of magnetic crosstalk between adjacent magnets in the compact Double Triple Bend Achromat (DTBA) lattice was investigated. Using Opera-3D magnetostatic simulation, six magnet pairs were analyzed to investigate the changes in magnetic field distribution along the electron trajectory and integrated magnetic field within each magnet aperture. The study employed polynomial and Fourier analyses to calculate multipole field components. Results indicate that magnetic crosstalk affects the field distribution in the region between magnets, particularly for the defocusing quadrupole and dipole magnets (QD2-D01) and the focusing quadrupole and octupole magnets (QF42-OF1) pairs, which have the pole-to-pole distances of 153.37 mm and 116.45 mm, respectively. Although these separations exceed the estimated fringe field regions, deviations of up to 1% in the main field components were observed. Notably, even an unpowered neighboring magnet contributes to magnetic field distortion due to the modified magnetic flux distribution. Crosstalk effects on the higher-order multipole fields are mostly within the acceptable limit, except for the extra quadrupole field from QD2 found in the dipole D01 magnet. This study highlights the effects of magnetic interference in tightly packed lattice and underscores the need to include a complete multipole field data with crosstalk consideration in the SPS-II lattice model in order to ensure an accurate beam dynamics simulation and predict the operating current adjustments for machine commissioning.

Particles doi: 10.3390/particles8030079

Authors: Francesco Nozzoli Luigi Ernesto Ghezzer Francesco Bruni Daniele Corti Francesco Meinardi Riccardo Nicolaidis Leonardo Ricci Piero Spinnato Enrico Verroi Paolo Zuccon

The Cherenkov effect, whereby a charged particle emits light when traveling faster than the phase velocity of light in a dielectric medium, is widely employed in particle identification techniques. However, Cherenkov light yield is relatively low, typically amounting to only 100–200 visible photons per centimeter of path length in materials like water, plastic, or glass. In this study, we investigate the optical response of FB118, a wavelength-shifting (WLS) plastic developed by Glass to Power, under exposure to ionizing particles. Our measurements confirm the absence of residual scintillation in FB118, allowing for a clean separation of Cherenkov signals. Moreover, the intrinsic WLS properties of the material enable a significant enhancement of light detection in the visible range. These features make FB118 a promising candidate for use in compact Cherenkov detectors, particularly in astroparticle physics experiments where space and power constraints demand efficient, compact solutions.

Particles doi: 10.3390/particles8030078

Authors: Sakdinan Naeosuphap Sarunyu Chaichuay Siriwan Jummunt Porntip Sudmuang

The performance and beam quality of the new fourth-generation synchrotron light source with ultra-low emittance are highly susceptible to coupled-bunch instabilities. These instabilities arise from the interaction between the bunched electron beam and the surrounding vacuum chamber installations. To mitigate these effects, the installation of a transverse bunch-by-bunch feedback system is planned. This system will comprise a button-type beam position monitor (BPM) for beam signal detection, a digital feedback controller, a broadband power amplifier, and a broadband stripline kicker as the primary actuator. One of the critical challenges lies in the development of the stripline kicker, which must be optimized for high shunt impedance and wide bandwidth while minimizing beam-coupling impedance. This work focuses on the comprehensive design of the stripline kicker intended for transverse (horizontal and vertical) bunch-by-bunch feedback in the Siam Photon Source II (SPS-II) storage ring. The stripline kicker design also incorporates features to enable its use for beam excitation in the SPS-II tune measurement system. The optimization process involves analytical approximations and detailed numerical electromagnetic field analysis of the stripline’s 3D geometry, focusing on impedance matching, field homogeneity, power transmission, and beam-coupling impedance. The details of engineering design are discussed to ensure that it meets the fabrication possibilities and stringent requirements of the SPS-II accelerator.

Particles doi: 10.3390/particles8030077

Authors: Siriwan Jummunt Prapaiwan Sunwong Supachai Prawanta Thongchai Leetha Pajeeraporn Numanoy Netchanok Thiabsi Porntip Sudmuang

The development of a prototype booster magnet for the Siam Photon Source II (SPS-II) was launched in 2023 as a milestone in advancing accelerator technology through domestic manufacturing capabilities in Thailand. In the SPS-II booster lattice, the magnet integrates focusing quadrupole and sextupole functions into a combined-function quadrupole-sextupole magnet, enabling a more compact lattice and reducing the total number of magnets required. To meet the required magnet specifications, the design was carefully optimized using Opera-3D software (version 2021) to achieve a quadrupole gradient of 19.395 T/m and a sextupole gradient of 22.327 T/m2 over an effective magnetic length of 0.25 m, while maintaining a magnetic field homogeneity better than 1 × 10−3. A key manufacturing challenge involved fabricating laminated magnet cores and establishing precise production processes. Magnetic field measurements performed on the prototype using the Hall-probe technique validated the magnet’s quality and accuracy. This paper presents the overall development process, including the magnet design, details of the magnetic field simulation methodology, prototype fabrication, and initial magnetic field measurements.

Particles doi: 10.3390/particles8030076

Authors: Wanisa Promdee Sukho Kongtawong Surakawin Suebka Thapakron Pulampong Natthawut Suradet Roengrut Rujanakraikarn Puttimate Hirunuran Siriwan Jummunt

This study presents the development of a noise-monitoring system for the storage ring at the Siam Photon Source, designed to detect and classify noise patterns in real time using beam position monitor (BPM) data. Noise patterns were categorized into four classes: broad peak, multipeak, normal peak, and no beam. Two BPMs located at the multipole wiggler section, BPM-MPW1 and BPM-MPW2, were selected for detailed monitoring based on consistent noise trends observed across the ring. The dataset was organized in two complementary formats: two-dimensional (2D) images used for training and validating the models and one-dimensional (1D) CSV files containing the corresponding raw numerical signal data. Pre-trained deep learning and 1D convolutional neural network (CNN) models were employed to classify these patterns, achieving an overall classification accuracy of up to 99.83%. The system integrates with the EPICS control framework and archiver log data, enabling continuous data acquisition and long-term analyses. Visualization and monitoring features were developed using CS-Studio/Phoebus, providing both operators and beamline scientists with intuitive tools to track beam quality and investigate noise-related anomalies. This approach highlights the potential of combining beam diagnostics with machine learning to enhance operational stability and optimize the synchrotron radiation performance for user experiments.

Particles doi: 10.3390/particles8030075

Authors: Leo Weissman Asher Shor Sergey Vaintraub

We have tested the performance of spectroscopic single-crystal Chemical Vapor-Deposited (sCVD) diamond detectors with radioactive sources and with a pulsed deuterium-tritium neutron generator. The tests demonstrate that the detectors could provide good timing and spectroscopic information at high neutron fluxes. The spectroscopic information can be obtained at a 14 MeV neutron rate as high as 1010 n/cm2/s, despite some limitations associated with pulse character of the used neutron generator. Monte-Carlo simulations were performed in order to achieve better understanding of neutron interaction with the detector material. Possible applications for the use of the detectors at Soreq Applied Research Accelerator Facility (SARAF) are considered. The detectors could be used as reliable neutron rate monitors in the vicinity of a strong accelerator-based source of energetic neutrons. The detectors could also be utilized as time-of-flight tagging counters in nuclear physics experiments under condition of high neutron fluxes during short beam pulses. In particular, measurement of the 12C(n,n′)3α cross-section is discussed.

Particles doi: 10.3390/particles8030074

Authors: Rauf Mukhamedshin Turlan Sadykov Vladimir Galkin Alia Argynova Aidana Almenova Dauren Muratov Khanshaiym Makhmet Valery Zhukov Vladimir Ryabov Vyacheslav Piscal Yernar Tautayev Zhakypbek Sadykov

A number of phenomena were observed in experiments on the study of cosmic rays at mountain altitudes and in the stratosphere at ultra-high energies; in particular, the coplanarity of the most energetic particles and local subcascades in the so-called families of γ-rays and hadrons in the cores of extensive air showers at E0 ≳ 2·1015 eV (√s ≳ 2 TeV). These effects are not described by theoretical models. To explain this phenomenon, it may be necessary to introduce a new process of generating the most energetic particles in the interactions of hadrons with the nuclei of atmospheric atoms. A new experimental array of cosmic ray detectors, including the ADRON-55 ionization calorimeter, has been created to study processes in EAS cores at ultra-high energies. The possibility of using it to study the coplanarity effect is being considered.

Particles doi: 10.3390/particles8030073

Authors: Alexander Shepetov Aliya Baktoraz Orazaly Kalikulov Svetlana Mamina Yerzhan Mukhamejanov Kanat Mukashev Vladimir Ryabov Nurzhan Saduyev Turlan Sadykov Saken Shinbulatov Tairzhan Skokbayev Ivan Sopko Shynbolat Utey Ludmila Vildanova Nurzhan Yerezhep Valery Zhukov

For further investigation of the properties of the muon component in the core regions of extensive air showers (EASs), a new underground hodoscopic set-up with a total sensitive area of 22 m2 was built at the Tien Shan High Mountain Cosmic Ray Station. The hodoscope is based on a set of large-sized scintillation charged particle detectors with an output signal of analog type. The installation ensures a (5–8) GeV energy threshold of muon registration and a ∼104 dynamic range for the measurement of the density of muon flux. A program facility was designed that uses modern machine learning techniques for automated search for the typical scintillation pulse pattern in an oscillogram of a noisy analog signal at the output of the hodoscope detector. The program provides a ∼99% detection probability of useful signals, with a relative share of false positives below 1%, and has a sufficient operation speed for real-time analysis of incoming data. Complete verification of the hardware and software tools was performed under realistic operation conditions, and the results obtained demonstrate the correctness of the proposed method and its practical applicability to the investigation of the muon flux in EASs. In the course of the installation testing, a preliminary physical result was obtained concerning the rise of the multiplicity of muon particles around an EAS core in dependence on the primary EAS energy.

Particles doi: 10.3390/particles8030072

Authors: Kenta Hagihara Takashi Nakatsukasa Nobuo Hinohara

Nuclei are self-bound systems in which the strong interaction (nuclear force) plays a dominant role, and the isospin is approximately a good quantum number. The isospin symmetry is primarily violated by electromagnetic interactions, namely Coulomb interactions among protons, the effects of which need be studied to understand the importance of the isospin symmetry. We investigate the effect of the Coulomb interaction on nuclear properties, especially quadrupole deformation and neutron drip line, utilizing the density functional method, which provides a universal description of nuclear systems in the entire nuclear chart. We carry out calculations of even–even nuclei with a proton number of 2≤Z≤60. The results show that the Coulomb interaction plays a significant role in enhancing quadrupole deformation across a wide range of nuclei. We also find that, after including the Coulomb interaction, some nuclei near the neutron drip line become stable against two-neutron emissions, resulting in a shift in the drip line towards larger neutron numbers.

Particles doi: 10.3390/particles8030071

Authors: Hiroki Yamada Toshiya Muto Fujio Hinode Shigeru Kashiwagi Kenichi Nanbu Ikuro Nagasawa Kotaro Shibata Ken Takahashi Anjali Bhagwan Kavar Kodai Kudo Hayato Abiko Pitchayapak Kitisri Hiroyuki Hama

To evaluate the characteristics of Smith–Purcell radiation, we modified a surface current model to consider the geometrical shading effect of a grating, which was ignored in the original one, and compared it with measurements for a grating with a shallow blaze angle. According to the numerical calculations based on the surface current model with and without the shading effect, it was found that the azimuthal angular distribution, polarization components and the variation in radiation intensity with the blaze angle of the grating are predicted to show significantly different behaviors under our experimental conditions. Generating the coherent Smith–Purcell radiation using the very short electron bunch in the test accelerator, t-ACTS at the Research Center for Accelerator and Radioisotope Science, Tohoku University, we measured polarization and the angular distribution of radiation for the gratings with different blaze angles. This study supports the validity of the modified surface current model with the shading effect and will provide new insights into the evaluation of the characteristics of Smith–Purcell radiation.

Particles doi: 10.3390/particles8030070

Authors: Eduardo Fradkin

Complex phase diagrams are a generic feature of quantum materials that display high-temperature superconductivity. In addition to d-wave superconductivity (or other unconventional states), these phase diagrams typically include various forms of charge-ordered phases, including charge-density waves and/or spin-density waves, as well as electronic nematic states. In most cases, these phases have critical temperatures comparable in magnitude to that of the superconducting state and appear in a “pseudo-gap” regime. In these systems, the high temperature state does not produce a good metal with well-defined quasiparticles but a ”strange metal”. These states typically arise from doping a strongly correlated Mott insulator. With my collaborators, I have identified these behaviors as a problem with “Intertwined Orders”. A pair-density wave is a type of superconducting state that embodies the physics of intertwined orders. Here, I discuss the phenomenology of intertwined orders and the quantum materials that are known to display these behaviors.

Particles doi: 10.3390/particles8030069

Authors: Zachary Metzler Nicholas Kirschner Lucas Smith Nicholas Cannady Makoto Sasaki Daniel Shy Regina Caputo Carolyn Kierans Aleksey Bolotnikov Thomas J. Caligiure Gabriella A. Carini Alexander Wilder Crosier Jack Fried Priyarshini Ghosh Sean Griffin Jon Eric Grove Elizabeth Hays Sven Herrmann Emily Kong Iker Liceaga-Indart Julie McEnery John Mitchell Alexander A. Moiseev Lucas Parker Jeremy Perkins Bernard Phlips Adam J. Schoenwald Clio Sleator David J. Thompson Janeth Valverde Sambid Wasti Richard Woolf Eric Wulf Anna Zajczyk

ComPair, a prototype of the All-sky Medium Energy Gamma-ray Observatory (AMEGO), completed a short-duration high-altitude balloon campaign on 27 August 2023 from Fort Sumner, New Mexico, USA. The goal of the balloon flight was to demonstrate ComPair as both a Compton and Pair telescope in flight, reject the charged particle background, and measure the background γ-ray spectrum. This analysis compares measurements from the balloon flight with Monte Carlo simulations to benchmark the instrument. The comparison finds good agreement between the measurements and simulations and supports the conclusion that ComPair accomplished its goals for the balloon campaign. Additionally, two charged particle background rejection schemes are discussed: a soft ACD veto that records a higher charged particle event rate but with less risk of event loss, and a hard ACD veto that limits the charged particle event rate on board. There was little difference in the measured spectra from the soft and hard ACD veto schemes, indicating that the hard ACD veto could be used for future flights. The successes of ComPair’s engineering flight will inform the development of the next generation of ComPair with upgraded detector technology and larger active area.

Particles doi: 10.3390/particles8030068

Authors: Anjali Bhagwan Kavar Shigeru Kashiwagi Kai Masuda Toshiya Muto Fujio Hinode Kenichi Nanbu Ikuro Nagasawa Kotaro Shibata Ken Takahashi Hiroki Yamada Kodai Kudo Hayato Abiko Pitchayapak Kitisri Hiroyuki Hama

High-current electron beams can significantly enhance the productivity of variety of applications including medical radioisotope (RI) production and wastewater purification. High-power superconducting radio frequency (SRF) linacs are capable of producing such high-current electron beams due to the key advantage to operate in continuous wave (CW) mode. However, this requires an injector capable of generating electron bunches with high repetition rate and in CW mode, while minimizing beam losses to avoid damage to SRF cavities due to quenching. RF gating to the grid of a thermionic electron gun is a promising solution, as it ensures CW bunch generation at the repetition rate same as the fundamental or sub-harmonics of the accelerating RF frequency, with minimal beam loss. This paper presents detailed beam dynamics simulations demonstrating that an RF-gated gun operating at 1.3 GHz can generate bunches with 148 ps full width with 8.96 pC charge.

Particles doi: 10.3390/particles8030067

Authors: Marco A. López Joaquín Portilla Victor Etxebarria Iñigo Arredondo Jorge Feuchtwanger

The experimental and computational characterization of a cold model prototype designed to test the electromagnetic properties of a new RFQ (Radio-Frequency Quadrupole) cavity is reported. This cavity is intended to be an essential part of a compact, high-gradient proton accelerator for medical purposes. The RFQ’s design employs a novel RF power-coupler injection solution. One common way to couple the RF power in proton RFQs has been the use of loop-couplers inserted into the mid-section of the RFQ’s lobe sections. This technique has been demonstrated to be reliable and effective but introduces a significant perturbation into the lobe that can be more noticeable when dealing with compact structures. We propose a RF injection scheme that uses direct transition from a coaxial cable to the RFQ by connecting the inner coaxial conductor to the RFQ vane body. As a consequence, the lobe geometry is not perturbed, and the transversal electrical fields are directly excited through the vanes. Moreover, by using a pair of such couplers connected to opposite vanes at a given transversal plane of the RFQ, it is also possible to excite the desired quadrupolar TE210 modes while avoiding the excitation of dipolar TE110 modes. The resonances corresponding to different RFQ modes have been characterized, and the dependence of the amplitude of the modes on the relative phase of the field injected through the RF power ports has been demonstrated both by measurements and simulations.

Particles doi: 10.3390/particles8030066

Authors: Ekkachai Kongmon Kantaphon Damminsek Nopadon Khangrang Sakhorn Rimjaem Chitrlada Thongbai

This study presents the design and development of electromagnetic dipole magnets for use as beam dumps and spectrometers in the MIR and THz free-electron laser (FEL) beamlines at the PBP-CMU Electron Linac Laboratory (PCELL). The magnets were optimized to achieve a 60-degree bending angle for electron beams with energies up to 30 MeV, without requiring water cooling. Using CST EM Studio for 3D magnetic field simulations and ASTRA for particle tracking, the THz dipole (with 414 turns) and MIR dipole (with 600 turns) generated magnetic fields of 0.1739 T and 0.2588 T, respectively, while both operating at currents below 10 A. Performance analysis confirmed effective beam deflection, with the THz dipole showing that it was capable of handling beam energies up to 20 MeV and the MIR dipole could handle up to 30 MeV. The energy measurement at the spectrometer screen position was simulated, taking into account transverse beam size, fringe fields, and space charge effects, using ASTRA. The energy resolution, defined as the ratio of energy uncertainty to the mean energy, was evaluated for selected cases. For beam energies of 16 MeV and 25 MeV, resolutions of 0.2% and 0.5% were achieved with transverse beam sizes of 1 mm and 4 mm, respectively. All evaluated cases maintained energy resolutions below 1%, confirming the spectrometer’s suitability for high-precision beam diagnostics. Furthermore, the relationship between the initial and measured energy spread errors, taking into account a camera resolution of 0.1 mm/pixel, was evaluated. Simulations across various beam energies (10–16 MeV for the THz dipole and 20–25 MeV for the MIR dipole) confirmed that the measurement error in energy spread decreases with smaller RMS transverse beam sizes. This trend was consistent across all tested energies and magnet configurations. To ensure accurate energy spread measurements, a small initial beam size is recommended. Specifically, for beams with a narrow initial energy spread, a transverse beam size below 1 mm is essential.

Particles doi: 10.3390/particles8030065

Authors: Corey Sargent William Clark Antonia Seifert Alicia Mand Emerson Rogers Adam Lane Alexandre Deur Balša Terzić

We examine the claimed observations of a gravitational external field effect (EFE) reported by Chae et al. We show that observations suggestive of the EFE can be interpreted without violating Einstein’s equivalence principle, namely from known correlations between the morphology, the environment, and dynamics of galaxies. While Chae et al.’s analysis provides a valuable attempt at a clear test of modified Newtonian dynamics, an evidently important topic, a re-analysis of the observational data does not permit us to confidently assess the presence of an EFE or to distinguish this interpretation from that proposed in this article.

Particles doi: 10.3390/particles8030064

Authors: Kittipong Techakaew Kanlayaporn Kongmali Siriwan Pakluea Sakhorn Rimjaem

The generation of high-quality mid-infrared free-electron laser (MIR-FEL) radiation depends critically on precise control of electron beam parameters, including energy, energy spread, transverse emittance, bunch charge, and bunch length. At the PBP-CMU Electron Linac Laboratory (PCELL), effective beam diagnostics are essential for optimizing FEL performance. However, dedicated systems for direct measurement of transverse emittance and bunch length at the undulator entrance have been lacking. This paper addresses this gap by presenting the design, simulation, and analysis of diagnostic stations for accurate characterization of these parameters. A two-quadrupole emittance measurement system was developed, enabling independent control of beam-focusing in both transverse planes. An analytical model was formulated specifically for this configuration to enhance emittance reconstruction accuracy. Systematic error analysis was conducted using ASTRA beam dynamics simulations, incorporating 3D field maps from CST Studio Suite and fully including space-charge effects. Results show that transverse emittance values as low as 0.15 mm·mrad can be measured with less than 20% error when the initial RMS beam size is under 2 mm. Additionally, quadrupole misalignment effects were quantified, showing that alignment within ±0.95 mm limits systematic errors to below 33.3%. For bunch length measurements, a transition radiation (TR) station coupled with a Michelson interferometer was designed. Spectral and interferometric simulations reveal that transverse beam size and beam splitter properties significantly affect measurement accuracy. A 6% error due to transverse size was identified, while Kapton beam splitters introduced additional systematic distortions. In contrast, a 6 mm-thick silicon beam splitter enabled accurate, correction-free measurements. The finite size of the radiator was also found to suppress low-frequency components, resulting in up to 10.6% underestimation of bunch length. This work provides a practical and comprehensive diagnostic framework that accounts for multiple error sources in both transverse emittance and bunch length measurements. These findings contribute valuable insight for the beam diagnostics community and support improved control of beam quality in MIR FEL systems.

Particles doi: 10.3390/particles8030063

Authors: Héctor Gutiérrez Arance Luca Fiorini Alberto Valero Biot Francisco Hervás Álvarez Santiago Folgueras Carlos Vico Villalba Pelayo Leguina López Arantza Oyanguren Campos Valerii Kholoimov Volodymyr Svintozelskyi Jiahui Zhuo

The escalating demand for data processing in particle physics research has spurred the exploration of novel technologies to enhance the efficiency and speed of calculations. This study presents the development of an implementation of MADGRAPH, a widely used tool in particle collision simulations, to Field Programmable Gate Array (FPGA) using High-Level Synthesis (HLS). This research presents a proof of concept limited to a single, relatively simple process e+e−→μ+μ−. The experimental evaluation methodology is described, focusing on performance comparison between traditional CPU implementations, GPU acceleration, and the new FPGA approach. This study describes the complex process of adapting MADGRAPH to FPGA using HLS, focusing on optimizing algorithms for parallel processing. These advancements could enable faster execution of complex simulations, highlighting FPGA’s crucial role in advancing particle physics research. The encouraging results obtained in this proof of concept prove potential interest in testing the performance of the FPGA implementation of more complex processes.

Particles doi: 10.3390/particles8020062

Authors: Daria Yu. Sergeeva Alexey A. Tishchenko

Hollow electron beams are a promising tool for generating coherent radiation in various frequency ranges. Hollow beams have unique properties, including increased stability and the ability to achieve high current densities without significant deterioration of beam quality. This paper presents the results of a theoretical study on coherent grating transition radiation arising during the interaction between a relativistic hollow electron beam and a flat two-dimensional photonic crystal. The radiation field is calculated using the dipole approximation. Theoretical analysis has shown that, under certain conditions, a high degree of radiation coherence can be achieved. The results open up new possibilities for the creation of new sources of coherent terahertz radiation.

Particles doi: 10.3390/particles8020061

Authors: Kota Yoshinaga Noritaka Shimizu Takashi Nakatsukasa

Nuclear density functional theory (DFT) is able to reproduce the saturation properties of nuclear matter, as well as properties of finite nuclei. Consequently, the DFT calculations are applicable to nuclei across a wide range of masses on the nuclear chart. The Gogny-type density functional, which is equivalent to the mean-field calculations with finite-range density-dependent effective interactions, is a successful example. In contrast, the shell model (configuration interaction) calculation is a powerful tool to describe nuclear structure, especially spectroscopic properties. The shell model is able to take into account correlations beyond mean-field in a truncated model space. In this work, we report an investigation on sd-shell nuclei and Ca isotopes using a hybrid approach of the shell model and Gogny-type DFT.

Particles doi: 10.3390/particles8020060

Authors: Giovanni Gaudino

The Belle II experiment has collected a 364 fb−1 sample of collisions at the Υ(4S) resonance. This dataset, with its low particle multiplicity and well-constrained initial state, provides an ideal environment for studying semileptonic and missing energy B decays. In this paper, I will present recent results on these decays, emphasizing their impact on the determination of CKM matrix elements and potential new physics. I will also discuss the techniques used for missing energy reconstruction and the challenges of signal-background discrimination. Future analysis prospects with larger datasets will also be highlighted.

Particles doi: 10.3390/particles8020059

Authors: Zuman Zhang Sha Li Ning Yu Hongge Xu Yuanmeng Xiong Kun Liu

In ultra-relativistic heavy-ion collisions, the study of muons from kaon (K) and pion (π) decays provides insights into hadron production and propagation in the Quark–Gluon Plasma (QGP). This paper investigates muon yields from K and π decays in Pb–Pb collisions at sNN=2.76 TeV using a fast simulation method. We employ a fast Monte Carlo procedure to estimate muon yields from charged kaons and pions. The simulation involves generating pions and kaons with uniform pT and y distributions, simulating their decay kinematics via PYTHIA, and reweighting to match the physical spectra. Our results show the transverse momentum distributions of muons from K and π decays at forward rapidity (2.5<y<4.0) for different centrality classes. The systematic uncertainties are primarily from the mid-rapidity charged K/π spectra and rapidity-dependent RAA uncertainties. The muon yields from pion and kaon decays exhibit consistency across centrality classes in the pT range of 3–10 GeV/c. This study contributes to understanding hadronic interactions and decay kinematics in heavy-ion collisions, offering references for investigating pion and kaon decay channels and hot medium effects.

Particles doi: 10.3390/particles8020058

Authors: Andrea De Vita Abhishek Max Aehle Muhammad Awais Alessandro Breccia Riccardo Carroccio Long Chen Tommaso Dorigo Nicolas R. Gauger Ralf Keidel Jan Kieseler Enrico Lupi Federico Nardi Xuan Tung Nguyen Fredrik Sandin Kylian Schmidt Pietro Vischia Joseph Willmore

In this work we consider the problem of determining the identity of hadrons at high energies based on the topology of their energy depositions in dense matter, along with the time of the interactions. Using GEANT4 simulations of a homogeneous lead tungstate calorimeter with high transverse and longitudinal segmentation, we investigated the discrimination of protons, positive pions, and positive kaons at 100 GeV. The analysis focuses on the impact of calorimeter granularity by progressively merging detector cells and extracting features like energy deposition patterns and timing information. Two machine learning approaches, XGBoost and fully connected deep neural networks, were employed to assess the classification performance across particle pairs. The results indicate that fine segmentation improves particle discrimination, with higher granularity yielding more detailed characterization of energy showers. Additionally, the results highlight the importance of shower radius, energy fractions, and timing variables in distinguishing particle types. The XGBoost model demonstrated computational efficiency and interpretability advantages over deep learning for tabular data structures, while achieving similar classification performance. This motivates further work required to combine high- and low-level feature analysis, e.g., using convolutional and graph-based neural networks, and extending the study to a broader range of particle energies and types.

Particles doi: 10.3390/particles8020057

Authors: Qin Zhou Zhipan Li

This study investigates the masses and quadrupole deformations of even-Z nuclei within the range 8⩽Z⩽104 using the triaxial relativistic Hartree–Bogoliubov model (TRHB) with the PC-PK1 density functional. For odd-mass nuclei, the global minima were determined using the automatic blocking method and their dynamical correlation energies (DCEs) were approximated using the average values of neighboring even–even nuclei calculated from a microscopic, five-dimensional, collective Hamiltonian (5DCH). The mean-field results underestimate the binding energies of most open-shell nuclei, with an initial root–mean–square (rms) deviation of 2.56 MeV for 1223 even-Z nuclei. Incorporating DCEs significantly reduces this deviation to 1.36 MeV. Additionally, the descriptions of two-neutron and one-neutron separation energies are improved, with rms deviations decreasing to 0.75 MeV and 0.65 MeV, respectively. Further refinement through accounting for odd–even differences in DCEs reduces the rms deviations for binding energies and one-neutron separation energies to 1.30 MeV and 0.63 MeV, respectively. Regarding the quadrupole deformations, TRHB calculations reveal spherical shapes near shell and subshell closures, well-deformed shapes at the mid-shell, and rapid shape transitions in medium- and heavy-mass regions. Oblate shapes dominate in regions (Z,N)∼(14,14),(34,36), and (40,60), and the neutron-deficient Pb region, with notable odd–even shape staggering attributed to the blocking effect of the odd nucleon. Triaxial shapes are favored in the mass regions (Z,N)∼(60,76) and (76,116).

Particles doi: 10.3390/particles8020056

Authors: Necla Çakmak Najm Abdullah Saleh

We performed the microscopic calculation of β-decay properties for waiting-point nuclei with neutron-closed magic shells. Allowed Gamow–Teller (GT) and first-forbidden (FF) transitions were simulated using a schematic model (SM) for waiting-point N = 50,82 isotopes in the framework of a proton–neutron quasiparticle random phase approximation (pn-QRPA). The Woods–Saxon (WS) potential basis was used in our calculations. The pn-QRPA equations of allowed (GT) and (FF) transitions were utilized in both the particle–hole (ph) and particle–particle (pp) channels in the SM. We solved the secular equations of the GT and FF transitions for eigenvalues and eigenfunctions of the corresponding Hamiltonians. A spherical shape was assigned to each waiting-point nucleus in all simulations. Significantly, this study marks the first time that β-decay analysis has been applied to certain nuclei, including 82Ge50, 83As50, 84Se50, 85Br50 and 87Rb50 with N=50 isotones, and 132Sn82, 133Sb82, 134Te82, 135I82 and 137Cs82 with N=82 isotones. Since there is no prior theoretical research on these nuclei, this work is a unique addition to the field. We compared our results with the previous calculations and measured data, and our calculations agree with the experimental data and the other theoretical results.

Particles doi: 10.3390/particles8020055

Authors: Valentin Zakharov Oleg Teryaev Georgy Prokhorov

By chiral effects, one understands the manifestations of chiral gauge anomaly and of gravitational chiral anomaly in hydrodynamics. In the last two to three years, our understanding of chiral effects has considerably changed. Here, we present a mini-review of two topics: first, a shift in understanding symmetry, which underlies the chiral magnetic effect and second, the interpretation of the chiral kinematical effect uncovered recently.

Particles doi: 10.3390/particles8020054

Authors: Samuel Escrig Christophe Rappold

Building on the successful demonstration of hypernuclear spectroscopy using heavy-ion beams, the HypHI Collaboration is shifting its focus to investigating proton- and neutron-rich hypernuclei. A crucial component of this research is the implementation of a fragment separator, which facilitates the production and separation of rare isotope beams and is vital for accessing hypernuclei far from the stability line. High-precision spectroscopy of these exotic hypernuclei is planned to be conducted at GSI first, which will be followed by experiments at the FAIR facility utilizing the FRS and Super-FRS fragment separators. A thorough systematic investigation paired with an optimization analysis was employed to establish the most favorable experimental setup for producing high-isospin hypernuclei. Theoretical models describing heavy-ion-induced reactions and hypernuclear synthesis guided this process, which was complemented by Monte Carlo simulations to obtain experimental efficiencies for the production and transmission of the exotic secondary beams. The outlined methodology offers insights into the anticipated yields of HeΛ6, CΛ9, and a range of both proton- and neutron-rich hypernuclei.