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Particles, Volume 8, Issue 1 (March 2025) – 13 articles

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12 pages, 349 KiB  
Article
Surrogate Model for In-Medium Similarity Renormalization Group Method Using Dynamic Mode Decomposition
by Sota Yoshida
Particles 2025, 8(1), 13; https://doi.org/10.3390/particles8010013 (registering DOI) - 9 Feb 2025
Viewed by 66
Abstract
I propose a data-driven surrogate model for the In-Medium Similarity Renormalization Group (IMSRG) method using Dynamic Mode Decomposition (DMD). First, the Magnus formulation of the IMSRG is leveraged to represent the unitary transformation of many-body operators of interest. Then, snapshots of these operators [...] Read more.
I propose a data-driven surrogate model for the In-Medium Similarity Renormalization Group (IMSRG) method using Dynamic Mode Decomposition (DMD). First, the Magnus formulation of the IMSRG is leveraged to represent the unitary transformation of many-body operators of interest. Then, snapshots of these operators at different flow parameters are decomposed by DMD to approximate the IMSRG flow in a latent space. The resulting emulator accurately reproduces the asymptotic flow behavior while lowering computational costs. I demonstrate that the DMD-based emulator results in a three to five times speedup compared to the full IMSRG calculation in a few test cases based on the ground state properties of 56Ni, 16O, and 40Ca in realistic nuclear interactions. While this is still not an acceleration that is significant enough to enable us to fully quantify, e.g., statistical uncertainties using Bayesian methods, this work offers a starting point for constructing efficient surrogate models for the IMSRG. Full article
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14 pages, 628 KiB  
Article
Imprints of High-Density Nuclear Symmetry Energy on Crustal Fraction of Neutron Star Moment of Inertia
by Nai-Bo Zhang and Bao-An Li
Particles 2025, 8(1), 12; https://doi.org/10.3390/particles8010012 - 7 Feb 2025
Viewed by 263
Abstract
The density dependence of nuclear symmetry energy Esym(ρ) remains the most uncertain aspect of the equation of state (EOS) of supradense neutron-rich nucleonic matter. Utilizing an isospin-dependent parameterization of the nuclear EOS, we investigate the implications of the observational [...] Read more.
The density dependence of nuclear symmetry energy Esym(ρ) remains the most uncertain aspect of the equation of state (EOS) of supradense neutron-rich nucleonic matter. Utilizing an isospin-dependent parameterization of the nuclear EOS, we investigate the implications of the observational crustal fraction of the neutron star (NS) moment of inertia ΔI/I for the Esym(ρ). We find that symmetry energy parameters significantly influence the ΔI/I, while the EOS of symmetric nuclear matter has a negligible effect. In particular, an increase in the slope L and skewness Jsym of symmetry energy results in a larger ΔI/I, whereas an increase in the curvature Ksym leads to a reduction in ΔI/I. Moreover, the ΔI/I is shown to have the potential for setting a lower limit of symmetry energy at densities exceeding 3ρ0, particularly when L is constrained to values less than 60 MeV, thereby enhancing our understanding of supradense NS matter. Full article
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25 pages, 9252 KiB  
Article
Extensions of the Variational Method with an Explicit Energy Functional for Nuclear Matter with Spin-Orbit Force
by Kento Kitanaka, Toshiya Osuka, Tetsu Sato, Hayate Ichikawa and Masatoshi Takano
Particles 2025, 8(1), 11; https://doi.org/10.3390/particles8010011 - 7 Feb 2025
Viewed by 261
Abstract
Two extensions of the variational method with explicit energy functionals (EEFs) with respect to the spin-orbit force were performed. In this method, the energy per nucleon of nuclear matter is explicitly expressed as a functional of various two-body distribution functions, starting from realistic [...] Read more.
Two extensions of the variational method with explicit energy functionals (EEFs) with respect to the spin-orbit force were performed. In this method, the energy per nucleon of nuclear matter is explicitly expressed as a functional of various two-body distribution functions, starting from realistic nuclear forces. The energy was then minimized by solving the Euler–Lagrange equation for the distribution functions derived from the EEF. In the first extension, an EEF of symmetric nuclear matter at zero temperature was constructed using the two-body central, tensor, and spin-orbit nuclear forces. The energy per nucleon calculated using the Argonne v8’ two-body nuclear potential was found to be lower than those calculated using other many-body methods, implying that the energy contribution caused by the spin-orbit correlation, whose relative orbital angular momentum operator acts on other correlations, is necessary. In a subsequent extension, the EEF of neutron matter at zero temperature, including the spin-orbit force, was extended to neutron matter at finite temperatures using the method by Schmidt and Pandharipande. The thermodynamic quantities of neutron matter calculated using the Argonne v8’ nuclear potential were found to be reasonable and self-consistent. Full article
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28 pages, 23407 KiB  
Article
Confronting the Broken Phase of the N2HDM with Higgs Data
by Maien Binjonaid
Particles 2025, 8(1), 10; https://doi.org/10.3390/particles8010010 - 3 Feb 2025
Viewed by 512
Abstract
The broken phase of the next-to-two-Higgs-doublet model (N2HDM) constitutes an archetype of extended Higgs sectors. In the presence of a softly broken Z2 symmetry throughout the scalar and Yukawa sectors, as the additional gauge singlet field does not interact with fermions, the [...] Read more.
The broken phase of the next-to-two-Higgs-doublet model (N2HDM) constitutes an archetype of extended Higgs sectors. In the presence of a softly broken Z2 symmetry throughout the scalar and Yukawa sectors, as the additional gauge singlet field does not interact with fermions, the model admits four variants of Yukawa interactions between the doublets and Standard Model fermions. We confront each type with experimental Higgs data, especially those from CMS and ATLAS detectors at the LHC. Interfacing the models with the state-of-the-art package HiggsTools, we perform a statistical χ2 analysis to determine the best-fit points and exclusion limits at the 95% and 68% C.L.’s and identify SM-like Higgs measurements that affect each type the most. We further analyze the exclusion bounds on the additional Higgs bosons at the 95% C.L., paying special attention to searches for hypothetical non-SM Higgs resonances decaying into a pair of bosons or fermions. We show regions where the additional Higgs bosons do not satisfy the narrow-width approximation utilized in most experimental searches. Full article
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16 pages, 323 KiB  
Article
Derivation of Meson Masses in SU(3) and SU(4) Extended Linear Sigma Model at Finite Temperature
by Abdel Nasser Tawfik, Azar I. Ahmadov, Alexandra Friesen, Yuriy Kalinovsky, Alexey Aparin and Mahmoud Hanafy
Particles 2025, 8(1), 9; https://doi.org/10.3390/particles8010009 - 22 Jan 2025
Viewed by 529
Abstract
The present study focused on the mesonic potential contributions to the Lagrangian of the extended linear sigma model (eLSM) for scalar and pseudoscalar meson fields across various quark flavors. The present study focused on the low-energy phenomenology associated with quantum chromodynamics (QCD), where [...] Read more.
The present study focused on the mesonic potential contributions to the Lagrangian of the extended linear sigma model (eLSM) for scalar and pseudoscalar meson fields across various quark flavors. The present study focused on the low-energy phenomenology associated with quantum chromodynamics (QCD), where mesons and their interactions serve as the pertinent degrees of freedom, rather than the fundamental constituents of quarks and gluons. Given that SU(4) configurations are completely based on SU(3) configurations, the possible relationships between meson states in SU(3) and those in SU(4) were explored at finite temperature. Meson states, which are defined by distinct chiral properties, were grouped according to their orbital angular momentum J, parity P, and charge conjugation C. Consequently, this organization yielded scalar mesons with quantum numbers JPC=0++, pseudoscalar mesons with JPC=0+, vector mesons with JPC=1, and axial vector mesons with JPC=1++. We accomplished the derivation of analytical expressions for a total of seventeen noncharmed meson states and twenty-nine charmed meson states so that an analytical comparison of the noncharmed and charmed meson states at different temperatures became feasible and the SU(3) and SU(4) configurations could be analytically estimated. Full article
(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))
8 pages, 11915 KiB  
Article
Development of the NUCLEUS Detector to Explore Coherent Elastic Neutrino-Nucleus Scattering
by Nicole Schermer
Particles 2025, 8(1), 8; https://doi.org/10.3390/particles8010008 - 22 Jan 2025
Viewed by 479
Abstract
The NUCLEUS experiment, currently being commissioned at the Technical University of Munich, is designed to observe coherent elastic neutrino-nucleus scattering (CEνNS) from reactor neutrinos and measure its cross-section with a percent-level precision at recoil energies below 100 eV [...] Read more.
The NUCLEUS experiment, currently being commissioned at the Technical University of Munich, is designed to observe coherent elastic neutrino-nucleus scattering (CEνNS) from reactor neutrinos and measure its cross-section with a percent-level precision at recoil energies below 100 eV. As a Standard Model process, CEνNS provides a unique probe into neutrino properties, potential new physics, and background suppression techniques relevant to dark matter experiments. The experiment utilizes gram-scale cryogenic calorimeters operating at 10 mK with an energy threshold of 20 eV. Situated at a shallow overburden of 3 m of water equivalent, the experimental site necessitates an advanced shielding strategy combining active vetoes and passive layers to reduce background rates to approximately 100counts/(kg·day·keV), as confirmed by full setup simulations. The commissioning phase has successfully demonstrated the stable operation of the cryogenic target detectors, achieving baseline resolutions below 10 eV, and the integration of the various shielding systems. Following this milestone, the experiment is set to transition to the EdF Chooz B nuclear reactor in France in 2025, where it will enable precise measurements of CEνNS, contributing to the understanding of neutrino interactions and advancing the field of astroparticle physics. Full article
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7 pages, 308 KiB  
Review
Rare Decays in CMS
by Giacomo Fedi
Particles 2025, 8(1), 7; https://doi.org/10.3390/particles8010007 - 17 Jan 2025
Viewed by 307
Abstract
The CMS experiment at the LHC has advanced precision measurements of rare B-meson and charm decays, offering insights into phenomena beyond the Standard Model (SM). This paper highlights key results from Run 2 and Run 3 data, including the branching fraction and lifetime [...] Read more.
The CMS experiment at the LHC has advanced precision measurements of rare B-meson and charm decays, offering insights into phenomena beyond the Standard Model (SM). This paper highlights key results from Run 2 and Run 3 data, including the branching fraction and lifetime of Bsμ+μ, angular analyses of B0K*0μ+μ, the first observation of J/ψμ+μμ+μ, and stringent limits on D0μ+μ. These findings provide tests of SM predictions while probing subtle hints of new physics. Full article
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6 pages, 4345 KiB  
Article
The HIBEAM Experiment
by Alexander Burgman
Particles 2025, 8(1), 6; https://doi.org/10.3390/particles8010006 - 16 Jan 2025
Viewed by 318
Abstract
The violation of baryon number is an essential ingredient for baryogenesis—the preferential creation of matter over antimatter—needed to account for the observed baryon asymmetry in the universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed [...] Read more.
The violation of baryon number is an essential ingredient for baryogenesis—the preferential creation of matter over antimatter—needed to account for the observed baryon asymmetry in the universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units as follows: free neutron–antineutron oscillation via mixing, neutron–antineutron oscillation via regeneration from a sterile neutron state, and neutron disappearance; the effective process of neutron regeneration is also possible. The program can be used to discover and characterize mixing in the neutron, antineutron, and sterile neutron sectors. The experiment addresses topical open questions such as the origins of baryogenesis and the nature of dark matter, and it is sensitive to scales of new physics that substantially exceed those available at colliders. A goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches, which is a rare opportunity. A conceptual design report for NNBAR has recently been published. Full article
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9 pages, 1080 KiB  
Review
Lepton Flavour Universality Tests Using Semileptonic b-Hadron Decays at the LHCb Detector
by Bogdan Kutsenko
Particles 2025, 8(1), 5; https://doi.org/10.3390/particles8010005 - 14 Jan 2025
Viewed by 362
Abstract
This review highlights advancements in testing Lepton Flavour Universality (LFU) through semileptonic b-hadron decays at the LHCb detector. Measurements of the LFU R(D) and R(D*) provide evidence of deviations from Standard Model (SM) predictions, suggesting [...] Read more.
This review highlights advancements in testing Lepton Flavour Universality (LFU) through semileptonic b-hadron decays at the LHCb detector. Measurements of the LFU R(D) and R(D*) provide evidence of deviations from Standard Model (SM) predictions, suggesting the presence of possible New Physics (NP). However, the D longitudinal polarisation results are in good agreement with SM expectations, placing constraints on potential NP theories, such as the leptoquarks or charged Higgs models. Further improvements in the measurements’ precision are expected with the new data from LHCb Run 3, collected with higher instantaneous luminosity and improved trigger. Full article
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7 pages, 473 KiB  
Article
An Overview of the CMS High Granularity Calorimeter
by Bora Akgün
Particles 2025, 8(1), 4; https://doi.org/10.3390/particles8010004 - 11 Jan 2025
Viewed by 333
Abstract
Calorimetry at the High Luminosity LHC (HL-LHC) faces many challenges, particularly in the forward direction, such as radiation tolerance and large in-time event pileup. To meet these challenges, the CMS Collaboration is preparing to replace its current endcap calorimeters from the HL-LHC era [...] Read more.
Calorimetry at the High Luminosity LHC (HL-LHC) faces many challenges, particularly in the forward direction, such as radiation tolerance and large in-time event pileup. To meet these challenges, the CMS Collaboration is preparing to replace its current endcap calorimeters from the HL-LHC era with a high-granularity calorimeter (HGCAL), featuring an unprecedented transverse and longitudinal segmentation, for both the electromagnetic and hadronic compartments, with 5D information (space–time–energy) read out. The proposed design uses silicon sensors for the electromagnetic section (with fluences above 1016 neq/cm2) and high-irradiation regions (with fluences above 1014 neq/cm2) of the hadronic section, while in the low-irradiation regions of the hadronic section, plastic scintillator tiles equipped with on-tile silicon photomultipliers (SiPMs) are used. Full HGCAL will have approximately 6 million silicon sensor channels and about 280 thousand channels of scintillator tiles. This will allow for particle-flow-type calorimetry, where the fine structure of showers can be measured and used to enhance particle identification, energy resolution and pileup rejection. In this overview we present the ideas behind HGCAL, the current status of the project, results of the beam tests and the challenges that lie ahead. Full article
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9 pages, 15387 KiB  
Article
The Transmission Muography Technique for Locating Potential Radon Gas Conduits at the Temperino Mine (Tuscany, Italy)
by Diletta Borselli, Tommaso Beni, Lorenzo Bonechi, Debora Brocchini, Nicola Casagli, Roberto Ciaranfi, Vitaliano Ciulli, Raffaello D’Alessandro, Andrea Dini, Catalin Frosin, Giovanni Gigli, Sandro Gonzi, Silvia Guideri, Luca Lombardi, Massimiliano Nocentini, Andrea Paccagnella and Simone Vezzoni
Particles 2025, 8(1), 3; https://doi.org/10.3390/particles8010003 - 11 Jan 2025
Viewed by 383
Abstract
Transmission muography is an imaging technique that allows us to obtain two-dimensional and three-dimensional average-target density images by measuring the transmission of atmospheric muons. Through this technique, it is possible to observe density anomalies inside a target volume and locate them three-dimensionally. In [...] Read more.
Transmission muography is an imaging technique that allows us to obtain two-dimensional and three-dimensional average-target density images by measuring the transmission of atmospheric muons. Through this technique, it is possible to observe density anomalies inside a target volume and locate them three-dimensionally. In this work, the potential of the technique will be illustrated through the description of the results of two measurements carried out in the tourist path of the Temperino mine (Livorno, Italy) in an area where a higher concentration of Radon gas is measured. This section of the gallery, located at a depth of about 50 m and dating back to the Etruscan period, might contain ancient cavities not yet discovered that could represent preferential conduits into which Radon gas is released into the tourist route. The muographic results are illustrated, focusing on the search for low-density anomalies attributable to cavities. The measurements are part of the MIMA-SITES project aimed at ensuring the safety of specific zones within the Temperino mine. Full article
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13 pages, 387 KiB  
Article
Examination of Possible Proton Magic Number Z = 126 with the Deformed Relativistic Hartree-Bogoliubov Theory in Continuum
by Cong Pan and Xin-Hui Wu
Particles 2025, 8(1), 2; https://doi.org/10.3390/particles8010002 - 2 Jan 2025
Viewed by 549
Abstract
Whether Z=126 is a proton magic number has been controversial in nuclear physics. The even-even Ubh126 isotopes are calculated based on the DRHBc calculations with PC-PK1. The evolutions of quadrupole deformation and pairing energies for neutron and proton are analyzed [...] Read more.
Whether Z=126 is a proton magic number has been controversial in nuclear physics. The even-even Ubh126 isotopes are calculated based on the DRHBc calculations with PC-PK1. The evolutions of quadrupole deformation and pairing energies for neutron and proton are analyzed to study the possible nuclear magicity. Spherical shape occurs and neutron pairing energy vanishes at N=258 and 350, which are the results of possible neutron magicity, while the proton pairing energy never vanishes in Ubh isotopes, which does not support the proton magicity at Z=126. In the single-proton spectrum, there is no discernible gap at Z=126, while significant gaps appear at Z=120 and 138. Therefore, Z=126 is not supported as a proton magic number, while Z=120 and 138 are suggested as candidates of proton magic numbers. Full article
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19 pages, 433 KiB  
Review
Electromagnetic Field and Radiation of Charged Particles in the Vicinity of Schwarzschild Black Hole
by Stanislav Komarov and Gregory Vereshchagin
Particles 2025, 8(1), 1; https://doi.org/10.3390/particles8010001 - 30 Dec 2024
Viewed by 525
Abstract
We provide a concise review of the problem of calculating the electromagnetic field and radiation of a charged particle in the vicinity of a black hole. The interest in this problem has been revived due to recent progress in multimessenger observations. Many astrophysical [...] Read more.
We provide a concise review of the problem of calculating the electromagnetic field and radiation of a charged particle in the vicinity of a black hole. The interest in this problem has been revived due to recent progress in multimessenger observations. Many astrophysical models of energy extraction from a black hole involve consideration of such motion and radiation. Our main goal is to highlight the basic assumptions and limitations of various techniques and point out the main conclusions of these studies. Full article
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