Physics

26 pages, 4856 KiB

Open AccessArticle

PREFACE: A Search for Long-Lived Particles at the Large Hadron Collider

by Burak Hacisahinoglu, Suat Ozkorucuklu, Maksym Ovchynnikov, Michael G. Albrow, Aldo Penzo and Orhan Aydilek

Physics 2025, 7(3), 33; https://doi.org/10.3390/physics7030033 (registering DOI) - 1 Aug 2025

Abstract

The Standard Model (SM) fails to explain many problems (neutrino masses, dark matter, and matter–antimatter asymmetry, among others) that may be resolved with new particles beyond the SM. No observation of such new particles may be explained either by their exceptionally high mass [...] Read more.

The Standard Model (SM) fails to explain many problems (neutrino masses, dark matter, and matter–antimatter asymmetry, among others) that may be resolved with new particles beyond the SM. No observation of such new particles may be explained either by their exceptionally high mass or by considerably small coupling to SM particles. The latter case implies relatively long lifetimes. Such long-lived particles (LLPs) then to have signatures different from those of SM particles. Searches in the “central region” are covered by the LHC general purpose experiments. The forward small angle region far from the interaction point (IP) is unexplored. Such particles are expected to have the energy as large as E =

O

(1 TeV) and Lorentz time dilation factor

γ = E / m \approx 10^{2}

–

10^{3}

(with m the particle mass) hence long enough decay distances. A new class of specialized LHC detectors dedicated to LLP searches has been proposed for the forward regions. Among these experiments, FASER is already operational, and FACET is under consideration at a location 100 m from the LHC IP5 (the CMS detector intersection). However, some features of FACET require a specially enlarged beam pipe, which cannot be implemented for LHC Run 4. In this study, we explore a simplified version of the proposed detector PREFACE compatible with the standard LHC beam pipe in the HL-LHC Run 4. Realistic Geant4 simulations are performed and the background is evaluated. An initial analysis of the physics potential with the PREFACE geometry indicates that several significant channels could be accessible with sensitivities comparable to FACET and other LLP searches. Full article

(This article belongs to the Section High Energy Physics)

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15 pages, 6245 KiB

Open AccessArticle

Investigation of Charging Effect on an Isolated Conductor Based on a Monte Carlo Simulation

by Haotian Chen, Shifeng Mao and Zejun Ding

Physics 2025, 7(3), 32; https://doi.org/10.3390/physics7030032 (registering DOI) - 1 Aug 2025

Abstract

We report calculations of charging effect on an isolated conductor, gold nanosphere, under electron beam bombardment at primary electron energies of 0.1–10 keV based on an up-to-date Monte Carlo simulation method. The calculations consider electron flow in sample, in which the electron yield [...] Read more.

We report calculations of charging effect on an isolated conductor, gold nanosphere, under electron beam bombardment at primary electron energies of 0.1–10 keV based on an up-to-date Monte Carlo simulation method. The calculations consider electron flow in sample, in which the electron yield is almost equivalent to the case when the electron flow is not considered. The electron yields and charging spatial distribution are obtained. For comparison, the calculation for bulk conductor is also performed, for which the time average of electric potential is found to reproduce the law of electrostatics. Full article

(This article belongs to the Section Applied Physics)

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12 pages, 736 KiB

Open AccessArticle

Hybrid Framework of Fermi–Dirac Spin Hydrodynamics

by Zbigniew Drogosz

Physics 2025, 7(3), 31; https://doi.org/10.3390/physics7030031 (registering DOI) - 1 Aug 2025

Abstract

The paper outlines the hybrid framework of spin hydrodynamics, combining classical kinetic theory with the Israel–Stewart method of introducing dissipation. The local equilibrium expressions for the baryon current, the energy–momentum tensor, and the spin tensor of particles with spin 1/2 following the Fermi–Dirac [...] Read more.

The paper outlines the hybrid framework of spin hydrodynamics, combining classical kinetic theory with the Israel–Stewart method of introducing dissipation. The local equilibrium expressions for the baryon current, the energy–momentum tensor, and the spin tensor of particles with spin 1/2 following the Fermi–Dirac statistics are obtained and compared with the earlier derived versions where the Boltzmann approximation was used. The expressions in the two cases are found to have the same form, but the coefficients are shown to be governed by different functions. The relative differences between the tensor coefficients in the Fermi–Dirac and Boltzmann cases are found to grow exponentially with the baryon chemical potential. In the proposed formalism, nonequilibrium processes are studied including mathematically possible dissipative corrections. Standard conservation laws are applied, and the condition of positive entropy production is shown to allow for the transfer between the spin and orbital parts of angular momentum. Full article

(This article belongs to the Special Issue High Energy Heavy Ion Physics—Zimányi School 2024)

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14 pages, 959 KiB

Open AccessArticle

Exploring Hidden Sectors with Two-Particle Angular Correlations at Future e⁺e⁻ Colliders

by Emanuela Musumeci, Adrián Irles, Redamy Pérez-Ramos, Imanol Corredoira, Edward Sarkisyan-Grinbaum, Vasiliki A. Mitsou and Miguel Ángel Sanchis-Lozano

Physics 2025, 7(3), 30; https://doi.org/10.3390/physics7030030 - 22 Jul 2025

Viewed by 283

Abstract

Future

e^{+} e^{-}

colliders are expected to play a fundamental role in measuring Standard Model (SM) parameters with unprecedented precision and in probing physics beyond the SM (BSM). This study investigates two-particle angular correlation distributions involving final-state SM charged hadrons. Unexpected [...] Read more.

Future

e^{+} e^{-}

colliders are expected to play a fundamental role in measuring Standard Model (SM) parameters with unprecedented precision and in probing physics beyond the SM (BSM). This study investigates two-particle angular correlation distributions involving final-state SM charged hadrons. Unexpected correlation structures in these distributions is considered to be a hint for new physics perturbing the QCD partonic cascade and thereby modifying azimuthal and (pseudo)rapidity correlations. Using Pythia8 Monte Carlo generator and fast simulation, including selection cuts and detector effects, we study potential structures in the two-particle angular correlation function. We adopt the QCD-like Hidden Valley (HV) scenario as implemented in Pythia8 generator, with relatively light HV v-quarks (below about 100 GeV), to illustrate the potential of this method. Full article

(This article belongs to the Section High Energy Physics)

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11 pages, 1218 KiB

Open AccessCommunication

Spin Polarization Crossing a Heterostructure of a Ferromagnetic/Semiconductor-Based Rashba Spin–Orbit Interaction: Tight Binding Approach

by Aek Jantayod

Physics 2025, 7(3), 29; https://doi.org/10.3390/physics7030029 - 17 Jul 2025

Viewed by 233

Abstract

The spin polarization of current in a conventional ferromagnetic and semiconductor-based Rashba spin–orbit interaction (RSOI) in an infinite two-dimensional system and the electrical properties of the junction are described using the square lattice model. In particular, a suitable approach is devised to compute [...] Read more.

The spin polarization of current in a conventional ferromagnetic and semiconductor-based Rashba spin–orbit interaction (RSOI) in an infinite two-dimensional system and the electrical properties of the junction are described using the square lattice model. In particular, a suitable approach is devised to compute the particle transport characteristics in the junction, taking into consideration the interface quality. It is found that the spin polarization becomes strongly reliant on the spin-flip scattering potential at applied voltages close to the crossings of the semiconductor-based RSOI band. On the other hand, in the voltage near the middle band, the spin polarization of current is found to remain modest and not influenced by either the spin-flip or non-spin-flip scattering potentials. Full article

(This article belongs to the Section Classical Physics)

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32 pages, 3005 KiB

Open AccessReview

Photophysical Process of Hypocrellin-Based Photodynamic Therapy: An Efficient Antimicrobial Strategy for Overcoming Multidrug Resistance

by Pazhani Durgadevi, Koyeli Girigoswami and Agnishwar Girigoswami

Physics 2025, 7(3), 28; https://doi.org/10.3390/physics7030028 - 15 Jul 2025

Viewed by 442

Abstract

The emergence of multidrug-resistant (MDR) bacteria and biofilm-associated infections has created a significant hurdle for conventional antibiotics, prompting the exploration of alternative strategies. Photodynamic therapy (PDT), a technique that utilizes photosensitizers activated by light to produce ROS, has emerged as a beacon of [...] Read more.

The emergence of multidrug-resistant (MDR) bacteria and biofilm-associated infections has created a significant hurdle for conventional antibiotics, prompting the exploration of alternative strategies. Photodynamic therapy (PDT), a technique that utilizes photosensitizers activated by light to produce ROS, has emerged as a beacon of hope in the fight against MDR microorganisms. Among the natural photosensitizers, hypocrellins (A and B) have shown remarkable potential with their dual-mode photodynamic action, generating ROS via both Type I (electron transfer) and Type II (singlet oxygen) pathways. This unique action disrupts bacterial biofilms and inactivates MDR pathogens. The amphiphilic nature of hypocrellins further enhances their promise, enabling deep biofilm penetration and ensuring potent antibacterial effects even in hypoxic environments, surpassing the capabilities of synthetic photosensitizers. This study critically examines the antimicrobial properties of hypocrellin-based PDT, emphasizing its mechanisms, advantages over traditional antibiotics, and effectiveness against MDR pathogens. Comparative analysis with other photosensitizers, the role of nanotechnology-enhanced delivery systems, and future clinical applications are explored. Its combination with nanotechnology enhances therapeutic outcomes, providing a viable alternative to conventional antibiotics. Further clinical research is essential to optimize its application and integration into antimicrobial treatment protocols. Full article

(This article belongs to the Section Biophysics and Life Physics)

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12 pages, 3178 KiB

Open AccessArticle

Terahertz Optoelectronic Properties of Monolayer MoS₂ in the Presence of CW Laser Pumping

by Ali Farooq, Wen Xu, Jie Zhang, Hua Wen, Qiujin Wang, Xingjia Cheng, Yiming Xiao, Lan Ding, Altayeb Alshiply Abdalfrag Hamdalnile, Haowen Li and Francois M. Peeters

Physics 2025, 7(3), 27; https://doi.org/10.3390/physics7030027 - 14 Jul 2025

Viewed by 317

Abstract

Monolayer (ML) molybdenum disulfide (MoS₂) is a typical valleytronic material which has important applications in, for example, polarization optics and information technology. In this study, we examine the effect of continuous wave (CW) laser pumping on the basic optoelectronic properties of [...] Read more.

Monolayer (ML) molybdenum disulfide (MoS₂) is a typical valleytronic material which has important applications in, for example, polarization optics and information technology. In this study, we examine the effect of continuous wave (CW) laser pumping on the basic optoelectronic properties of ML MoS₂ placed on a sapphire substrate, where the pump photon energy is larger than the bandgap of ML MoS₂. The pump laser source is provided by a compact semiconductor laser with a 445 nm wavelength. Through the measurement of THz time-domain spectroscopy, we obtain the complex optical conductivity for ML MoS₂, which are found to be fitted exceptionally well with the Drude–Smith formula. Therefore, we expect that the reduction in conductivity in ML MoS₂ is mainly due to the effect of electronic backscattering or localization in the presence of the substrate. Meanwhile, one can optically determine the key electronic parameters of ML MoS₂, such as the electron density n_e, the intra-band electronic relaxation time τ, and the photon-induced electronic localization factor c. The dependence of these parameters upon CW laser pump intensity is examined here at room temperature. We find that 445 nm CW laser pumping results in the larger n_e, shorter τ, and stronger c in ML MoS₂ indicating that laser excitation has a significant impact on the optoelectronic properties of ML MoS₂. The origin of the effects obtained is analyzed on the basis of solid-state optics. This study provides a unique and tractable technique for investigating photo-excited carriers in ML MoS₂. Full article

(This article belongs to the Section Applied Physics)

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9 pages, 244 KiB

Open AccessCommunication

Derivation of the Ray Equation from Snell’s Law

by Carmen Toro-Castillo, Joel Cervantes-Lozano, David I. Serrano-García and Héctor O. González-Ochoa

Physics 2025, 7(3), 26; https://doi.org/10.3390/physics7030026 - 9 Jul 2025

Viewed by 307

Abstract

The one-dimensional ray equation, the differential description of Fermat’s principle, is deduced directly from Snell’s law using two methods. In the first method, we obtain the ray equation from a differential equation relating the spatial coordinates derivative with the index of refraction field. [...] Read more.

The one-dimensional ray equation, the differential description of Fermat’s principle, is deduced directly from Snell’s law using two methods. In the first method, we obtain the ray equation from a differential equation relating the spatial coordinates derivative with the index of refraction field. In the second method, the ray equation is deduced from the proper generalization of Snell’s law for a refractive field, that is, a differential equation relating the index of refraction field and the refraction angle. Additionally, we used an intermediate expression of the first method to find a straightforward analytical solution of the ray path to an inferior mirage. Full article

(This article belongs to the Section Physics Education)

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19 pages, 23214 KiB

Open AccessArticle

Quantum Scattering by Multiple Slits—A Lippmann–Schwinger Approach

by Rafael M. Fortiny, Matheus E. Pereira and Alexandre G. M. Schmidt

Physics 2025, 7(3), 25; https://doi.org/10.3390/physics7030025 - 1 Jul 2025

Viewed by 284

Abstract

We investigate the non-relativistic scattering of a plane wave by a vertical segment formulating the problem in terms of the Lippmann–Schwinger equation in two spatial dimensions. Adjusting the coupling strength function we show how to implement the scattering by a system of multiple [...] Read more.

We investigate the non-relativistic scattering of a plane wave by a vertical segment formulating the problem in terms of the Lippmann–Schwinger equation in two spatial dimensions. Adjusting the coupling strength function we show how to implement the scattering by a system of multiple slits and by a Cantor set. We present detailed calculations of the scattered wave function for the line segment, as well as for the single, double, and multiple slits. We define reflection and transmission functions that are position-dependent in a defined region. From these results, we obtain the probability densities and differential and total cross-sections for these problems. Full article

(This article belongs to the Section Classical Physics)

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19 pages, 568 KiB

Open AccessArticle

Testing the Double-Logarithmic Asymptotic Gluon Density in Ultraperipheral Heavy-Ion Collisions at the Large Hadron Collider

by Daniel Almeida Fagundes and Magno V. T. Machado

Physics 2025, 7(3), 24; https://doi.org/10.3390/physics7030024 - 25 Jun 2025

Cited by 1 | Viewed by 236

Abstract

In this paper, we analyze the application of an analytical gluon distribution based on double-asymptotic scaling to the photoproduction of vector mesons in coherent

p p

,

p A

, and

A A

collisions at LHC energies, using the color dipole formalism. Predictions [...] Read more.

In this paper, we analyze the application of an analytical gluon distribution based on double-asymptotic scaling to the photoproduction of vector mesons in coherent

p p

,

p A

, and

A A

collisions at LHC energies, using the color dipole formalism. Predictions for the rapidity distribution are presented for

ρ^{0}

,

J / ψ

,

ψ (2 S)

, and

Υ (1 S)

mesons photoproduction. An analysis of the uncertainties associated with different implementations of the dipole–proton amplitude is performed. The vector meson photoproduction accompanied by electromagnetic dissociation is also analyzed. Full article

(This article belongs to the Section High Energy Physics)

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