Particles

Natural supersymmetry with light higgsinos is most favored to emerge from the string landscape, since the volume of a scan parameter space shrinks to tiny volumes for electroweak unnatural models. Rather general arguments favor a landscape selection of soft SUSY breaking terms tilted to large values, but they are tempered by the atomic principle that the derived value of the weak scale in each pocket universe lies not too far from its measured value in our universe. But, that leaves (at least) three different paradigms for gaugino masses in natural SUSY models: unified (as in nonuniversal Higgs models), anomaly mediation form (as in natural AMSB), and mirage mediation form (with comparable moduli- and anomaly-mediated contributions). We perform landscape scans for each of these, and we show that they populate different, but overlapping, positions in $m(\mathit{\ell }\overline{\ell })$ and $m\left(wino\right)$ space. The first of these may be directly measurable at high-lumi LHC via the soft opposite-sign dilepton plus jets plus $E{/}_T$ signature arising from higgsino pair production, while the second of these could be extracted from direct wino pair production, leading to same-sign diboson production. Full article

A joint study of multi-particle pseudo-rapidity correlations and event-by-event fluctuations in the distributions of secondary particles and fragments of the target nucleus and the projectile nucleus was carried out in order to search for correlated clusters of secondary particles. An analysis of the collisions of the sulfur nucleus with photoemulsion nuclei at an energy of 200 A·GeV is presented based on experimental data obtained at the SPS at CERN. The analysis of multi-particle correlations was performed using the Hurst method. A detailed analysis of each individual event showed that in events of complete destruction of a projectile nucleus with a high multiplicity of secondary particles, long-distance multi-particle pseudo-rapidity correlations are observed. The distribution of average pseudo-rapidity in such events differs significantly from others, as it is much narrower, and its average value is noticeably shifted towards lower values <η>. Full article

In this review, we begin with a historical survey of some singular solutions in the theory of gravitation, as well as a very brief discussion of how black holes could physically form. Some possible scenarios which could perhaps eliminate these singularities are then reviewed and discussed. Due to the vastness of the field, its coverage is not exhaustive; instead, the concentration is on a small subset of topics such as possible quantum gravity effects, non-commutative geometry, and gravastars. A simple singularity theorem is also reviewed. Although parts of the manuscript assume some familiarity with relativistic gravitation or differential geometry, the aim is for the broad picture to be accessible to non-specialists of other physical sciences and mathematics. Full article

In our recent publications, we presented neutral-current $\nu$–nucleus cross-sections for the coherent and incoherent channels for some stable Mo isotopes, assuming a Mo detector medium, within the context of the deformed shell model. In these predictions, however, we have not included the contributions in the cross-sections stemming from the stable ^94,96Mo isotopes (abundance of ⁹⁴Mo 9.12% and of ⁹⁶Mo 16.50%). The purpose of the present work is to perform detailed calculations of $\nu$–^94,96Mo scattering cross-sections, for a given energy $E_{\nu }$ of the incoming neutrino, for coherent and incoherent processes. In many situations, the $E_{\nu }$ values range from 15 to 30 MeV, and in the present work, we used $E_{\nu }$ = 15 MeV. Mo as a detector material has been employed by the MOON neutrino and double-beta decay experiments and also from the NEMO neutrinoless double-beta decay experiment. For our cross-section calculations, we utilize the Donnelly–Walecka multipole decomposition method in which the $\nu$–nucleus cross-sections are given as a function of the excitation energy of the target nucleus. Because only the coherent cross-section is measured by current experiments, it is worth estimating what portion of the total cross-section represents the measured coherent rate. This requires the knowledge of the incoherent cross-section, which is also calculated in the present work. Full article

Black hole X-ray binary systems consist of a black hole accreting mass from its binary companion, forming an accretion disk. As a result, twin relativistic plasma ejections (jets) are launched towards opposite and perpendicular directions. Moreover, multiple broadband emission observations from X-ray binary systems range from radio to high-energy gamma rays. The emission mechanisms exhibit thermal origins from the disk, stellar companion, and non-thermal jet-related components (i.e., synchrotron emission, inverse comptonization of less energetic photons, etc.). In many attempts at fitting the emitted spectra, a static black hole is often assumed regarding the accretion disk modeling, ignoring the Kerr metric properties that significantly impact the geometry around the usually rotating black hole. In this work, we study the possible implications of the spin inclusion in predictions of the X-ray binary spectrum. We mainly focus on the most significant aspect inserted by the Kerr geometry, the innermost stable circular orbit radius dictating the disk’s inner boundary. The outcome suggests a higher-peaked and hardened X-ray spectrum from the accretion disk and a substantial increase in the inverse Compton component of disk-originated photons. Jet-photon absorption is also heavily affected at higher energy regimes dominated by hadron-induced emission mechanisms. Nevertheless, a complete investigation requires the full examination of the spin contribution and the resulting relativistic effects beyond the disk truncation. Full article

We investigate the cosmological evolution of the universe for a spatially flat FLRW background space within the context of $f(T,B)$ gravity, which is a recently formulated teleparallel theory that connects both $f\left(T\right)$ and $f\left(R\right)$ gravity under suitable limits. The analysis focuses on four different $f(T,B)$ cosmological models corresponding to various choices of scale factor, namely, emergent, logamediate, and intermediate. In addition to this, we assume a power law-like function of $f(T,B)$ gravity. The reconstruction of $f(T,B)$ gravity considers the Holographic Ricci Dark Energy (HRDE) as the background fluid. We analyze the equation of state parameters and the squared speed of sound for the reconstructed models. Finally, we conduct a thermodynamical analysis for each reconstructed model. The generalized second law of thermodynamics (GSLT) is valid for the four different $f(T,B)$ cosmological models. Full article

A thorough understanding of nuclear reaction rates at low energies is essential for improving our understanding of energy generation in stars and primordial and stellar nucleosynthesis. At low energies, fusion reactions between charged particles are strongly suppressed by the presence of the Coulomb barrier, which classically inhibits the penetration of one nucleus into another. The barrier penetration causes the cross section to have a steep energy dependence at low energies, making cross section measurements very challenging. Furthermore, little is known about the impact of surrounding electrons in stellar plasmas that are currently beyond the reach of experiments. As a result, measuring the bare cross sections as accurately as possible is essential. Reaction rate measurements at very low energies have been made possible in recent years by the development of high-current low-energy accelerators as well as enhanced target and detection methods. Nevertheless, the presence of atomic electrons, which alter the Coulomb barrier by screening the nuclear charge and increase the cross section at low energies compared to the case of bare nuclei, complicates these observations. A review of the experimental and corresponding theoretical work on laboratory electron screening performed so far will be presented. Full article

A black hole’s spin effects on the jet emissions of high-energy neutrinos and $\gamma$-rays from black hole X-ray binary systems (BHXRBs) are investigated. The BHXRBs consist of a stellar black hole, a companion (donor) star, a BH accretion disk, a BH corona, and two jets emitted from the black hole perpendicular to the accretion disk. For their description, properties of the accretion disk, specifically the accretion disk’s inner radius $R_{in}$ and the accretion disk’s temperature profile $T\left(R\right)$, play key roles since they depend on the black hole’s dimensionless spin parameter ${\alpha }_{\ast }$. In this work, we focus on the main reaction mechanisms taking place inside jets from which high-energy $\gamma$-rays and neutrinos are created. The intensities and integral fluxes of neutrinos and $\gamma$-rays are obtained by integrating the respective source functions. Lastly, the $\gamma$-ray absorption due to $e^{-}$-$e^{+}$ pair production is considered, particularly absorption from the accretion disk. For concrete applications, we have chosen the BHXRB systems MAXI J1820+070, XTE J1550-564, and XTE J1859+226. Full article

The direct detection of dark matter constituents, particularly weakly interacting massive particles (WIMPs), is central to particle physics and cosmology. In this paper, we develop the formalism for WIMP–nucleus-induced transitions from isomeric nuclear states, with particular focus on the experimentally interesting target ¹⁸⁰Ta. Full article

The precessing jets of microquasar SS 433 have punched through the supernova remnant W 50 from the explosion forming the compact object. The jets collimate before reaching beyond the shell, some 40 pc downstream, just the region of origin of TeV gamma radiation. Collimation could be effected by ambient pressure in the SNR cavity; I investigate conditions under which the W 50 morphology and the sites of TeV gamma radiation can be explained in terms of collimation, with associated shocks, induced by ambient pressure. The SNR is now ~${10}^5$ years after the supernova; with the present pressure, collimation and associated shocks would indeed occur ~40 pc downstream. Modeling of the evolution of binary systems indicates that the Roche lobe overflow and the initiation of the jets may be recent rather than early; present day collimation would still occur ~40 pc downstream, but the cone angle of the precession must then have increased with time—driven by the Roche lobe overflow. The morphology of W 50 and the site of the origin of TeV radiation are readily explained in terms of the collimation of the jets by internal SNR pressure. Full article

In the last few decades, galactic stellar black hole X-ray binary systems (BHXRBs) have aroused intense observational and theoretical research efforts specifically focusing on their multi-messenger emissions (radio waves, X-rays, $\gamma$-rays, neutrinos, etc.). In this work, we investigate jet emissions of high-energy neutrinos and gamma-rays created through several hadronic and leptonic processes taking place within the jets. We pay special attention to the effect of the black hole’s spin (Kerr black holes) on the differential fluxes of photons originating from synchrotron emission and inverse Compton scattering and specifically on their absorption due to the accretion disk’s black-body radiation. The black hole’s spin (dimensionless spin parameter $a_{*}$) enters into the calculations through the radius of the innermost circular orbit around the black hole, the $R_{ISCO}$ parameter, assumed to be the inner radius of the accretion disk, which determines its optical depth ${\tau }_{disk}$. In our results, the differential photon fluxes after the absorption effect are depicted as a function of the photon energy in the range $1$GeV $\le E\le {10}^3$GeV. It is worth noting that when the black holes’ spin (${\alpha }_{*}$) increases, the differential photon flux becomes significantly lower. Full article

We propose a model for the QCD running coupling constant based on the analytical inverse QCD coupling constant concept with an additional regularization in the low momentum region. Analyticity in the $q^2$-complex plane, where q is the four-momentum transfer, is imposed by methods of the Analytic Perturbation Theory. The model incorporates a peculiar low-momentum behavior for ${\alpha }_s(q^2)$ as a divergence at $q^2=0$ to retrieve color confinement, without spoiling its correct high-momentum behavior. This was achieved by means of a two-parameter regularization function, for which we considered three possible analytic expressions. In fact, within the framework of the Analytic Perturbation Theory, ${\alpha }_s(q^2)$ assumes a finite value for $q^2=0$, at all perturbative orders (infrared stability), hence the infrared divergence cannot be implemented. For this reason, we found it more straightforward to work with its reciprocal, namely, ${\epsilon }_s(q^2)=1/{\alpha }_s(q^2)$, imposing its vanishing at the origin of the $q^2$-complex plane via the multiplication of the aforementioned regularizing functions and the spectral density. Once the two free parameters of the regularization functions were settled by fitting to the experimental values of ${\alpha }_s(q^2)$ at the momenta where these data were available and reliable, the model could reproduce the QCD running coupling constant at any other momentum transferred. Full article

To study EAS cores (beams of most energetic particles near the shower axis) at E₀ ≳ 10¹⁵ eV (√s ≳ 2 TeV), which carry the most valuable information about the types of primary particles and the characteristics of their interactions in the atmosphere, a new set of detectors has been developed, including a high-altitude ionization calorimeter “ADRON-55”, located at a high-altitude scientific station on the Tien Shan. The first results of modeling the development of EAS from primary protons, main groups of nuclei and hypothetical strangelets at various energies, related to measurements with the “ADRON-55” calorimeter, are presented. Full article

This article explores wormhole solutions within the framework of Finsler geometry and the modified gravity theory. Modifications in gravitational theories, such as $f(\mathcal{R},\mathcal{T})$ gravity, propose alternatives that potentially avoid the exotic requirements. We derive the field equations from examining the conditions for Finslerian wormhole existence and investigate geometrical and material characteristics of static wormholes using a polynomial shape function in Finslerian space–time. Furthermore, we address energy condition violations for different Finsler parameters graphically. We conclude that the proposed models, which assume a constant redshift function, satisfy the necessary geometric constraints and energy condition violations indicating the presence of exotic matter at the wormhole throat. We also discuss the anisotropy factors of the wormhole models. The results are validated through analytical solutions and 3-D visualizations, contributing to the broader understanding of wormholes in Finsler-modified gravity contexts. Full article

A review of the landscape of CPT symmetry tests is presented, centered around the Standard-Model Extension and focusing on tests in the neutral meson system. A discussion of the relevant theories summarizes original ideas. It is followed by a short transition into phenomenology. A more detailed parameterization is presented. Various experiments are used to deliver an overview of testing CPT from every angle that the theory suggested and that the neutral meson (NM) system could accommodate. Full article

Recent advancements have shown tensions between observations and our current understanding of the Universe. Such observations may include the $H_0$ tension and massive galaxies at high redshift that are older than traditional galaxy formation models have predict. Since these observations are based on redshift as the primary distance indicator, a bias in the redshift may explain these tensions. While redshift follows an established model, when applied to astronomy it is based on the assumption that the rotational velocity of the Milky Way galaxy relative to the observed galaxies has a negligible effect on redshift. But given the mysterious nature of the physics of galaxy rotation, that assumption needed to be tested. The test was done by comparing the redshift of galaxies rotating in the same direction relative to the Milky Way to the redshift of galaxies rotating in the opposite direction relative to the Milky Way. The results show that the mean redshift of galaxies that rotate in the same direction relative to the Milky Way is higher than the mean redshift of galaxies that rotate in the opposite direction. Additionally, the redshift difference becomes larger as the redshift gets higher. The consistency of the analysis was verified by comparing data collected by three different telescopes, annotated using four different methods, released by three different research teams, and covering both the northern and southern ends of the galactic pole. All the datasets are in excellent agreement with each other, showing consistency in the observed redshift bias. Given the “reproducibility crisis” in science, all the datasets used in this study are publicly available, and the results can be easily reproduced. This observation could be the first direct empirical reproducible observation for the Zwicky’s “tired-light” model. Full article

To this day, the nature of dark matter (DM) remains elusive despite all our efforts. This type of matter has not been directly observed, so we infer its gravitational effect. Since galaxies and supermassive objects like these are most likely to contain DM, we assume that dense objects such as neutron stars (NSs) are also likely to host DM. The NS is considered the best natural laboratory for testing theories and collecting observational data. We mainly focus on two types of DM particles, fermions and bosons, with a mass range of [0.01–1.5] GeV and repulsive interactions of about [${10}^{-4}$–${10}^{-1}$] ${\mathrm{MeV}}^{-1}$. Using a two-fluid model to solve the TOV equations, we find stable configurations that span hundreds of kilometers and weigh tens or even hundreds of solar masses. To visualize results, we think of a giant invisible compact DM object and the NS in the center as the core, the only visible part. Stability criteria are met for these configurations, so collapsing into a black hole is unlikely. We go further and use this work for smaller formations that exist inside the mysterious Mass Gap. We also find stable configurations of 3–4 solar masses, with NS-DM mixing capable of describing the mass gap. Regardless, the present theoretical prediction, if combined with corresponding observations, could shed light on the existence of DM and even more on its fundamental properties. Full article

The High Intensity Muon Beams (HIMB) project at the Paul Scherrer Institute (PSI) will deliver muon beams with unprecedented intensities of up to ${10}^{10}\mathrm{muons}/\mathrm{s}$ for next-generation particle physics and material science experiments. This represents a hundredfold increase over the current state-of-the-art muon intensities, also provided by PSI. We performed beam dynamics optimisations and studies for the design of the HIMB beamlines MUH2 and MUH3 using Graphics Transport, Graphics Turtle, and G4beamline, the latter incorporating PSI’s own measured ${\pi }^{+}$ cross-sections and variance reduction. We initially performed large-scale beamline optimisations using asynchronous Bayesian optimisation with DeepHyper. We are now developing an island-based evolutionary optimisation code $\mathtt{glyfada}$ based on the Paradiseo framework, where we implemented Message Passing Interface (MPI) islands with OpenMP parallelisation within each island. Furthermore, we implemented an island model that is also suitable for high-throughput computing (HTC) environments with asynchronous communication via a Redis database. The code interfaces with the codes COSY INFINITY and G4beamline. The code $\mathtt{glyfada}$ will provide heterogeneous island model optimisation using evolutionary optimisation and local search methods, as well as part-wise optimisation of the beamline with automatic advancement through stages. We will use the $\mathtt{glyfada}$ for a future large-scale optimisation of the HIMB beamlines. Full article

We review and meta-analyze particle data and properties of hadrons with measured rest masses. The results of our study are summarized as follows. (1) The strong-force suppression of the repulsive Coulomb forces between quarks is sufficient to explain the differences between mass deficits in nucleons and pions (and only them), the ground states with the longest known mean lifetimes; (2) unlike mass deficits, the excitations in rest masses of all particle groups are effectively quantized, but the rules are different in baryons and mesons; (3) the strong field is aware of the extra factor of ${\vartheta }_{\mathrm{e}}=2$ in the charges (Q) of the positively charged quarks; (4) mass deficits incorporate contributions proportional to the mass of each valence quark; (5) the scaling factor of these contributions is the same for each quark in each group of particles, provided that the factor ${\vartheta }_{\mathrm{e}}=2$ is taken into account; (6) besides hypercharge (Y), the much lesser-known “strong charge” ($Q^{\prime }=Y-Q$) is very useful in SU(3) in describing properties of particles located along the right-leaning sides and diagonals of the weight diagrams; (7) strong decays in which $Q^{\prime }$ is conserved are differentiated from weak decays, even for the same particle; and (8) the energy diagrams of (anti)quark transitions indicate the origin of CP violation. Full article