Particles

21 pages, 571 KiB

Open AccessArticle

Hayward–Letelier Black Holes in AdS Spacetime

by Arun Kumar, Ashima Sood, Sushant Ghoshtokumar Ghosh and Aroonkumar Beesham

Particles 2024, 7(4), 1017-1037; https://doi.org/10.3390/particles7040062 - 20 Nov 2024

We analyze Hayward black holes (BHs) with a negative cosmological constant surrounded by a cloud of strings, which we designate Hayward–Letelier AdS BHs. These solutions can be obtained by coupling the Einstein equations with nonlinear electrodynamics and the energy–momentum tensor of clouds of [...] Read more.

We analyze Hayward black holes (BHs) with a negative cosmological constant surrounded by a cloud of strings, which we designate Hayward–Letelier AdS BHs. These solutions can be obtained by coupling the Einstein equations with nonlinear electrodynamics and the energy–momentum tensor of clouds of strings. We show that these solutions are no longer regular and have a curvature singularity at the center. In turn, we analyze the thermodynamics associated with these BHs by establishing the form of the Smarr formula and the first law of thermodynamics. We derive the expressions for the thermodynamic quantities such as pressure, temperature, heat capacity, Gibbs free energy, and isothermal compressibility. We explore the phase structure of these solutions by analyzing the behavior of the heat capacity and Gibbs free energy. These solutions exhibit a first-order phase transition, similar to van der Waals fluids. We also check the behavior of the thermodynamic quantities near the critical points and calculate the values of the critical exponents. This illustrates a robust analogy between our solutions and van der Waals fluids. Full article

(This article belongs to the Special Issue Selected Papers from "International Conference on Gravitation, Astrophysics, and Cosmology (ICGAC-2024)": Theory Confronts Observation — A Cosmic Scenario)

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13 pages, 320 KiB

Open AccessArticle

Structure of the Baryon Halo Around a Supermassive Primordial Black Hole

by Boris Murygin, Viktor Stasenko and Yury Eroshenko

Particles 2024, 7(4), 1004-1016; https://doi.org/10.3390/particles7040061 - 13 Nov 2024

Abstract

According to some theoretical models, primordial black holes with masses of more than 10⁸ solar masses could be born in the early universe, and their possible observational manifestations have been investigated in a number of works. Dense dark matter and baryon halos [...] Read more.

According to some theoretical models, primordial black holes with masses of more than 10⁸ solar masses could be born in the early universe, and their possible observational manifestations have been investigated in a number of works. Dense dark matter and baryon halos could form around such primordial black holes even at the pre-galactic stage (in the cosmological Dark Ages epoch). In this paper, the distribution and physical state of the gas in the halo are calculated, taking into account the radiation transfer from the central accreting primordial black hole. This made it possible to find the ionization radius, outside of which there are regions of neutral hydrogen absorption in the 21 cm line. The detection of annular absorption regions at high redshifts in combination with a central bright source may provide evidence of the existence of supermassive primordial black holes. We also point out the fundamental possibility of observing absorption rings with strong gravitational lensing on galaxy clusters, which weakens the requirements for the angular resolution of radio telescopes. Full article

(This article belongs to the Special Issue Selected Papers from XXVII Workshop “What Comes Beyond the Standard Models?”: New Trends in Particle Cosmology)

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20 pages, 1797 KiB

Open AccessArticle

Hyperon Production in Bi + Bi Collisions at the Nuclotron-Based Ion Collider Facility and Angular Dependence of Hyperon Spin Polarization

by Nikita S. Tsegelnik, Vadym Voronyuk and Evgeni E. Kolomeitsev

Particles 2024, 7(4), 984-1003; https://doi.org/10.3390/particles7040060 - 13 Nov 2024

Abstract

The strange baryon production in Bi + Bi collisions at

\sqrt{s_{N N}} = 9.0

GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, and their centrality dependence and the effect of [...] Read more.

The strange baryon production in Bi + Bi collisions at

\sqrt{s_{N N}} = 9.0

GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, and their centrality dependence and the effect of rapidity and transverse momentum cuts are studied. The rapidity distributions for

\bar{Λ}

,

Ξ

,

\bar{Ξ}

baryons are found to be systematically narrower than for

Λ

s. The

p_{T}

slope parameters for anti-hyperons vary more with centrality than those for hyperons. Restricting the accepted rapidity range to

| y | < 1

increases the slope parameters by 13–30 MeV, depending on the centrality class and the hyperon mass. Hydrodynamic velocity and vorticity fields are calculated, and the formation of two oppositely rotating vortex rings moving in opposite directions along the collision axis is found. The hyperon spin polarization induced by the medium vorticity within the thermodynamic approach is calculated, and the dependence of the polarization on the transverse momentum and rapidity cuts and on the centrality selection is analyzed. The cuts have stronger effect on the polarization of

Λ

and

Ξ

hyperons than on the corresponding anti-hyperons. The polarization signal is maximal for the centrality class, 60–70%. We show that, for the considered hyperon polarization mechanism, the structure of the vorticity field makes an imprint on the polarization signal as a function of the azimuthal angle in the transverse momentum plane,

ϕ_{H}

,

cos ϕ_{H} = p_{x} / p_{T}

. For particles with positive longitudinal momentum,

p_{z} > 0

, the polarization increases with

cos ϕ_{H}

, while for particles with

p_{z} < 0

it decreases. Full article

(This article belongs to the Special Issue Infinite and Finite Nuclear Matter (INFINUM))

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17 pages, 423 KiB

Open AccessArticle

Thermal Conductivity and Thermal Hall Effect in Dense Electron-Ion Plasma

by Arus Harutyunyan and Armen Sedrakian

Particles 2024, 7(4), 967-983; https://doi.org/10.3390/particles7040059 - 11 Nov 2024

Abstract

In this study, we examine thermal conductivity and the thermal Hall effect in electron-ion plasmas relevant to hot neutron stars, white dwarfs, and binary neutron star mergers, focusing on densities found in the outer crusts of neutron stars and the interiors of white [...] Read more.

In this study, we examine thermal conductivity and the thermal Hall effect in electron-ion plasmas relevant to hot neutron stars, white dwarfs, and binary neutron star mergers, focusing on densities found in the outer crusts of neutron stars and the interiors of white dwarfs. We consider plasma consisting of single species of ions, which could be either iron

{}^{56}{Fe}

or carbon

{}^{12}C

nuclei. The temperature range explored is from the melting temperature of the solid

T \sim 10^{9}

K up to

10^{11}

K. This covers both degenerate and non-degenerate electron regimes. We find that thermal conductivity increases with density and temperature for which we provide analytical scaling relations valid in different regimes. The impact of magnetic fields on thermal conductivity is also analyzed, showing anisotropy in low-density regions and the presence of the thermal Hall effect characterized by the Righi–Leduc coefficient. The transition froma degenerate to non-degenerate regime is characterized by a minimum ratio of thermal conductivity to temperature, which is analogous to the minimum observed already in the case of electrical conductivity. We provide also formulas fit to our numerical results, which can be used in dissipative magneto-hydrodynamics simulations of warm compact stars. Full article

(This article belongs to the Special Issue Selected Papers from "The Modern Physics of Compact Stars and Relativistic Gravity 2023")

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12 pages, 625 KiB

Open AccessArticle

On the Thermomechanics of Hadrons and Their Mass Spectrum

by Leonardo Chiatti

Particles 2024, 7(4), 955-966; https://doi.org/10.3390/particles7040058 - 11 Nov 2024

Abstract

A little-known thermomechanical relation between entropy and action, originally discovered by Boltzmann in the classical domain, was later reconsidered by de Broglie in relation to the wave–particle duality in the free propagation of single particles. In this paper, we present a version adapted [...] Read more.

A little-known thermomechanical relation between entropy and action, originally discovered by Boltzmann in the classical domain, was later reconsidered by de Broglie in relation to the wave–particle duality in the free propagation of single particles. In this paper, we present a version adapted to the phenomenological description of the hadronization process. The substantial difference with respect to the original de Broglie scheme is represented by the universality of the temperature at which the process occurs; this, in fact, coincides with the Hagedorn temperature. The main results are as follows: (1) a clear connection between the universality of the temperature and the existence of a confinement radius of the color forces; (2) a lower bound on the hadronic mass, represented by the universal temperature, in agreement with experimental data; and (3) a scale invariance, which allows the reproduction of the well-known hadronic mass spectrum solution of the statistical bootstrap model. The approach therefore presents a heuristic interest connected to the study of the strong interaction. Full article

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16 pages, 508 KiB

Open AccessArticle

A Probe into the Evolution of Primordial Perturbations in the f(T) Gravity Framework with Chaplygin Gas

by Sanjeeda Sultana, Surajit Chattopadhyay and Antonio Pasqua

Particles 2024, 7(4), 939-954; https://doi.org/10.3390/particles7040057 - 31 Oct 2024

Abstract

This work is focused on studying the cosmology of variable modified Chaplygin gas (VMCG) in the framework of exponential and logarithmic

f (T)

theory. The equation of state (EoS) for VMCG in exponential and logarithmic

f (T)

gravity shows [...] Read more.

This work is focused on studying the cosmology of variable modified Chaplygin gas (VMCG) in the framework of exponential and logarithmic

f (T)

theory. The equation of state (EoS) for VMCG in exponential and logarithmic

f (T)

gravity shows quintom behavior. Primordial perturbations were studied for VMCG in both exponential and logarithmic

f (T)

gravity, and it was observed that the potential increases with cosmic time t, and the scalar field decreases toward the minimum value of the potential. The squared speed of sound was positive, meaning that VMCG in both exponential and logarithmic

f (T)

gravity shows stability against small gravitational perturbations. Full article

(This article belongs to the Special Issue Selected Papers from "International Conference on Gravitation, Astrophysics, and Cosmology (ICGAC-2024)": Theory Confronts Observation — A Cosmic Scenario)

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12 pages, 838 KiB

Open AccessArticle

Decoding the Gaugino Code Naturally at High-Lumi LHC

by Howard Baer, Vernon Barger and Kairui Zhang

Particles 2024, 7(4), 927-938; https://doi.org/10.3390/particles7040056 - 17 Oct 2024

Abstract

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 [...] Read more.

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 (ℓ \bar{ℓ})

and

m (w i n o)

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

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9 pages, 1116 KiB

Open AccessArticle

Hurst Exponent and Event-by-Event Fluctuations in Relativistic Nucleus–Nucleus Collisions

by Anastasiya I. Fedosimova, Khusniddin K. Olimov, Igor A. Lebedev, Sayora A. Ibraimova, Ekaterina A. Bondar, Elena A. Dmitriyeva and Ernazar B. Mukanov

Particles 2024, 7(4), 918-926; https://doi.org/10.3390/particles7040055 - 15 Oct 2024

Abstract

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 [...] Read more.

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

(This article belongs to the Special Issue Feature Papers for Particles 2023)

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19 pages, 1025 KiB

Open AccessReview

Some Singular Spacetimes and Their Possible Alternatives

by Andrew DeBenedictis

Particles 2024, 7(4), 899-917; https://doi.org/10.3390/particles7040054 - 14 Oct 2024

Abstract

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 [...] Read more.

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

(This article belongs to the Special Issue Selected Papers from "International Conference on Gravitation, Astrophysics, and Cosmology (ICGAC-2024)": Theory Confronts Observation — A Cosmic Scenario)

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12 pages, 357 KiB

Open AccessArticle

Cross-Sections of Neutral-Current Neutrino Scattering on ^94,96Mo Isotopes

by T. S. Kosmas, R. Sahu and V. K. B. Kota

Particles 2024, 7(4), 887-898; https://doi.org/10.3390/particles7040053 - 4 Oct 2024

Abstract

In our recent publications, we presented neutral-current

ν

–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 [...] Read more.

In our recent publications, we presented neutral-current

ν

–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

ν

–^94,96Mo scattering cross-sections, for a given energy

E_{ν}

of the incoming neutrino, for coherent and incoherent processes. In many situations, the

E_{ν}

values range from 15 to 30 MeV, and in the present work, we used

E_{ν}

= 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

ν

–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

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8 pages, 285 KiB

Open AccessArticle

Implications of the Spin-Induced Accretion Disk Truncation on the X-ray Binary Broadband Emission

by Theodora Papavasileiou, Odysseas Kosmas and Theocharis Kosmas

Particles 2024, 7(4), 879-886; https://doi.org/10.3390/particles7040052 - 1 Oct 2024

Abstract

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 [...] Read more.

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

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23 pages, 1167 KiB

Open AccessArticle

Cosmological Models within f(T, B) Gravity in a Holographic Framework

by Khandro K. Chokyi and Surajit Chattopadhyay

Particles 2024, 7(3), 856-878; https://doi.org/10.3390/particles7030051 - 22 Sep 2024

Abstract

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 (T)

and [...] Read more.

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 (T)

and

f (R)

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

(This article belongs to the Special Issue Selected Papers from "International Conference on Gravitation, Astrophysics, and Cosmology (ICGAC-2024)": Theory Confronts Observation — A Cosmic Scenario)

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22 pages, 568 KiB

Open AccessReview

Electron Screening in Laboratory Nuclear Reactions

by Jelena Vesić

Particles 2024, 7(3), 834-855; https://doi.org/10.3390/particles7030050 - 15 Sep 2024

Abstract

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 [...] Read more.

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

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16 pages, 900 KiB

Open AccessArticle

Black Hole’s Spin-Dependence of γ-Ray and Neutrino Emissions from MAXI J1820+070, XTE J1550-564, and XTE J1859+226

by Dimitrios Rarras, Odysseas Kosmas, Theodora Papavasileiou and Theocharis Kosmas

Particles 2024, 7(3), 818-833; https://doi.org/10.3390/particles7030049 - 12 Sep 2024

Cited by 1

Abstract

A black hole’s spin effects on the jet emissions of high-energy neutrinos and

γ

-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, [...] Read more.

A black hole’s spin effects on the jet emissions of high-energy neutrinos and

γ

-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_{i n}

and the accretion disk’s temperature profile

T (R)

, play key roles since they depend on the black hole’s dimensionless spin parameter

α_{*}

. In this work, we focus on the main reaction mechanisms taking place inside jets from which high-energy

γ

-rays and neutrinos are created. The intensities and integral fluxes of neutrinos and

γ

-rays are obtained by integrating the respective source functions. Lastly, the

γ

-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

(This article belongs to the Special Issue Testing Fundamental QED and BSM Physics Theories in Leptonic and Hadronic Processes)

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8 pages, 361 KiB

Open AccessArticle

Theoretical WIMP–Nucleus Scattering Rates for Isomeric Nuclei

by John D. Vergados and Dennis Bonatsos

Particles 2024, 7(3), 810-817; https://doi.org/10.3390/particles7030048 - 10 Sep 2024

Cited by 1

Abstract

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 ¹⁸⁰ [...] Read more.

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

(This article belongs to the Special Issue Selected Papers from “Physics beyond the Standard Model in Leptonic & Hadronic Processes and Relevant Computing Tools”)

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5 pages, 1174 KiB

Open AccessArticle

W 50 Morphology and the Dynamics of SS 433 Formation—The Origin of TeV Gammas from the Microquasar

by Michael Bowler

Particles 2024, 7(3), 805-809; https://doi.org/10.3390/particles7030047 - 4 Sep 2024

Abstract

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. [...] Read more.

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

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13 pages, 324 KiB

Open AccessArticle

Galactic Stellar Black Hole Binaries: Spin Effects on Jet Emissions of High-Energy Gamma-Rays

by Dimitrios Rarras, Theocharis Kosmas, Theodora Papavasileiou and Odysseas Kosmas

Particles 2024, 7(3), 792-804; https://doi.org/10.3390/particles7030046 - 3 Sep 2024

Cited by 1

Abstract

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,

γ

-rays, neutrinos, etc.). In this work, we investigate jet emissions of high-energy [...] Read more.

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,

γ

-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_{I S C O}

parameter, assumed to be the inner radius of the accretion disk, which determines its optical depth

τ_{d i s k}

. 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

\leq E \leq 10^{3}

GeV. It is worth noting that when the black holes’ spin (

α_{*}

) increases, the differential photon flux becomes significantly lower. Full article

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12 pages, 1133 KiB

Open AccessArticle

Analytical Inverse QCD Coupling Constant Approach and Its Result for α_s

by Rocco Malaspina, Lorenzo Pierini, Olga Shekhovtsova and Simone Pacetti

Particles 2024, 7(3), 780-791; https://doi.org/10.3390/particles7030045 - 30 Aug 2024

Cited by 1

Abstract

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 [...] Read more.

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

α_{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,

α_{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,

ε_{s} (q^{2}) = 1 / α_{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

α_{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

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12 pages, 9394 KiB

Open AccessArticle

Simulations of the EAS Development in the Atmosphere and Detectors for Experiments with the High-Altitude Ionization Calorimeter ADRON-55

by Turlan Sadykov, Omarkhan Yelemessov, Rauf Mukhamedshin, Vladimir Galkin, Alia Argynova, Korlan Argynova, Khanshaiym Makhmet, Valery Zhukov, Vladimir Ryabov and Yerkin Khussainov

Particles 2024, 7(3), 768-779; https://doi.org/10.3390/particles7030044 - 28 Aug 2024

Abstract

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 [...] Read more.

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

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