Search

We present results on simultaneous observations of Class I methanol masers at 25, 36, and 44 GHz towards 22 Galactic targets carried out with the Effelsberg 100-m telescope. The study investigates relations between the hyperfine (HF) structure of the torsion–rotation transitions in CH |$_3$| OH and maser activity. By analysing the radial velocity shifts between different maser lines together with the patterns of the HF structure based on laboratory measurements and quantum-chemical calculations, we find that in any source only one specific HF transition forms the maser emission and that this transition changes from source to source. The physical conditions leading to this selective behaviour are still unclear. Using accurate laboratory rest frequencies for the 25 GHz transitions, we have refined the centre frequencies for the HF multiplets at 36, 44, and 95 GHz: |$f_{\scriptscriptstyle 36} = (36169.2488\pm 0.0002_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz. |$f_{\scriptscriptstyle 44} = (44069.4176\pm 0.0002_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz, and |$f_{\scriptscriptstyle 95} = (95169.4414\pm 0.0003_{\scriptscriptstyle \rm stat} \pm 0.0004_{\scriptscriptstyle \rm sys})$|  MHz. Comparison with previous observations of 44 GHz masers performed 6–10 yr ago with a Korean 21-m Korean Very Long Baseline Interferometry Network telescope towards the same targets confirms the kinematic stability of Class I maser line profiles during this time interval and reveals a systematic radial velocity shift of |$0.013\pm 0.005$|  km s |$^{-1}$| between the two telescopes. [ABSTRACT FROM AUTHOR]

In the absence and presence of a circularly polarized monochromatic electromagnetic pulse, we have analyzed the electron–nucleon scattering process, where the nucleon is assumed to be spinless with a spherical shape. We have provided the theoretical calculation of the differential cross section (DCS) by using the Dirac–Volkov formalism. This research paper aims to provide two comparisons: We first compare the DCS in the absence of the laser field with its corresponding laser-assisted DCS. A second comparison is made between the electron–proton and electron–neutron scattering processes to study the effect of the laser on both processes. The results obtained about the effect of the laser field on the DCS and the electric form factor have been discussed for both scattering processes. We have found that the DCS is reduced when the laser field is applied for both processes. In addition, the form factor is also decreased by raising the incident electron energy in electron–proton scattering, but it increases in electron–neutron scattering. Moreover, the form factors for both scattering situations are unchanged by raising the laser field strength up to 1 0 8 V/cm. [ABSTRACT FROM AUTHOR]

Motivated by conceptual problems in quantum theories of gravity, the gravitational eikonal approach, inspired by its electromagnetic predecessor, has been successfully applied to the transplanckian energy collisions of elementary particles and strings since the late eighties, and to string-brane collisions in the past decade. After the direct detection of gravitational waves from black-hole mergers, most of the attention has shifted towards adapting these methods to the physics of black-hole encounters. For such systems, the eikonal exponentiation provides an amplitude-based approach to calculate classical gravitational observables, thus complementing more traditional analytic methods such as the Post-Newtonian expansion, the worldline formalism, or the Effective-One-Body approach. In this review we summarize the main ideas and techniques behind the gravitational eikonal formalism. We discuss how it can be applied in various different physical setups involving particles, strings and branes and then we mainly concentrate on the most recent developments, focusing on massive scalars minimally coupled to gravity, for which we aim at being as self-contained and comprehensive as possible. [ABSTRACT FROM AUTHOR]

In proton therapy, the protons are used to destroy the cancer cells efficiently at the Bragg peak without much damage to normal cells. The protons can also produce neutrons, protons, and high-energy gamma rays through nuclear reactions with cancerous and healthy tissues as well as with beamline components. The effective observed dose in the therapy is enhanced due to the interaction of nuclear particles with cancerous tissues. Such nuclear particles can have several effects on drugs used in immunotherapy, such as immunotherapy in combination with proton therapy, which has been used to treat cancer. In the present investigations, the gamma, neutron, and protons interaction parameters of some immunotherapy drugs, such as dostarlimab, atezolizumab, ipilimumab, nivolumab, and pembrolizumab, are determined by using EpiXs, NGCal, and PSTAR software. It is found that the EBF and EABF for all selected immunotherapy drugs increase with increasing penetration depth, peaking at 100 keV. The peaking is more symmetric at a higher penetration depth of 40 mfp than at a lower one of 1 mfp. At lower energies of gamma photons, the EBF values increase exponentially, and at higher energies, they increase linearly with increasing penetration depth for all selected drugs. Mass attenuation factors are slightly higher for thermal neutrons than for fast neutrons for selected immunotherapeutic drugs, indicating that thermal neutrons more actively participate in these drugs than fast neutrons. The mass attenuation factor for both fast and thermal neutrons increases with increasing weight percentages of hydrogen and is found to be higher for thermal neutrons. This is the first study in the literature to investigate the radiation interaction parameters for immunotherapy drugs, and it is helpful in radiation therapy and dosimetry. [ABSTRACT FROM AUTHOR]

Weakly interacting massive particles (WIMPs) may interact with a virtual pion that is exchanged between nucleons. This interaction channel is important to consider in models where the spin-independent isoscalar channel is suppressed. Using data from the first science run of the LUX-ZEPLIN dark matter experiment, containing 60 live days of data in a 5.5 tonne fiducial mass of liquid xenon, we report the results on a search for WIMP-pion interactions. We observe no significant excess and set an upper limit of 1.5 × 10−46 cm2 at a 90% confidence level for a WIMP mass of 33 GeV/c2 for this interaction. Cosmological evidence suggests that nonluminous dark matter comprises 27% of the energy density of the universe, with weakly interacting massive particles (WIMPs) being a favoured candidate. Here, the authors perform a search for WIMP-like dark matter interacting with a virtual particle that is exchanges between xenon nucleons. [ABSTRACT FROM AUTHOR]

The basic tribological experiments have reported that nano-graphene lubricating oil has excellent anti-friction and anti-wear properties, which has been widely concerned. However, the real anti-friction effect of nano-graphene lubricating oil and its impact on engine power performance, economic performance and emission performance remain to be proved. This has seriously hindered the popularization and application of nano-graphene lubricating oil in the engine field. In this paper, nano-graphene powder was chemically grafted to prepare nano-graphene lubricating oil with high dispersion stability. The influence of nano-graphene on physicochemical properties of lubricating oil was studied, and the influence of nano-graphene on engine power performance, economic performance and emission performance was explored. The results show that after modification, the dispersion of nano-graphene in lubricating oil is improved. Compared with pure lubricating oil, the addition of nano-graphene makes the kinematic viscosity of lubricating oil slightly lower, and has little effect on the density, flash point, pour point and total acid value of lubricating oil. The reversed towing torque of nano-graphene lubricating oil is reduced by 1.82–5.53%, indicating that the friction loss decreases. The specific fuel consumption of the engine is reduced, which indicates that the fuel economic performance is improved. Engine HC+NOX, CH4, CO2 emissions do not change much, but particulate matter (PM) emissions increase by 8.85%. The quantity concentration of nuclear particles, accumulated particles and total particles of nano-graphene lubricating oil are significantly higher than that of pure lubricating oil. And the increase of the quantity concentration of accumulated particles is more obvious than that of nuclear particles, and the larger the load, the more obvious this phenomenon. In order to apply nano-graphene lubricating oil to the engine, it is also necessary to further study its impact on the post-processing system, adjust the control strategy of the post-processing system and then test and calibrate. [ABSTRACT FROM AUTHOR]

We re-examine the effects of pairing gaps on charge-changing transitions and the associated β -decay half-lives. Calculations are performed using the proton-neutron quasiparticle random phase approximation (pn-QRPA) model for 250 nuclei possessing astrophysical significance. Pairing gaps between like nucleons are key model parameters in the pn-QRPA approach. Three different values of empirically computed pairing gaps were used as input parameters in our nuclear model. Changing the pairing gap values significantly altered the Gamow-Teller distributions including the total strength and centroid values. The β -decay half-lives also changed substantially. The half-lives computed via the three-term pairing formula, based on separation energies of nucleons, were in best agreement with the measured data. [ABSTRACT FROM AUTHOR]

We propose a novel systematization of positron-decaying atomic nuclei, for which we first focus on determining the kinetic energy of the most energetic positron at the moment it is emitted from the nucleus. We find that this energy is inversely proportional to the number of nucleons A making up the nucleus. Further on, for A > 6 0 , we figure out that the measured kinetic energy of positrons detected in the laboratory turns out to be substantially less than what one would classically expect based on the electrical interaction between the nucleus and the positron, starting from the moment the latter gets emitted. We particularly disclose that the initial kinetic energy of the positron escaping from the nucleus can be formally negative at A > 6 0 , which indicates that the positron in question is not released from the classically conceived nuclear surface, but from much above the said surface. This requires the need to involve the quantum mechanical properties of the system composed of "the nucleus and the positron". Finally, we show how the half-life, mass, kinetic energy and size involved in positron-decay are interrelated in a way already established through Yarman's approach (YA) for polyatomic molecules and α -decaying nuclei. [ABSTRACT FROM AUTHOR]

An improved semi-empirical formula for cluster radioactivity half-lives is proposed by incorporating the influences of reduced mass, the blocking effect of unpaired nucleons and mass asymmetry on the basis of the original Tavares formula [Eur. Phys. J. A 49 (2013) 6]. Using this improved semi-empirical formula, the calculated results of the cluster radioactivity half-lives for the daughter nuclei around 2 0 8 Pb or its neighbors can reproduce the experimental data well with a corresponding root-mean-square deviation σ = 0.570, which proves the feasibility of this formula to calculate cluster radioactivity half-lives in trans-lead nuclei. The accuracy of the improved semi-empirical formula is improved by approximately 37% compared to its predecessor whose the root-mean-square deviation is 0.902. Meanwhile, the influence of deformation effect for cluster radioactivity is also briefly discussed. In addition, we extend this improved semi-empirical formula to predict the half-lives of 51 possible cluster radioactive candidates whose cluster radioactivity are energetically allowed or observed but not yet quantified in NUBASE2020. For comparison, some empirical and/or semi-empirical formulae are also used. [ABSTRACT FROM AUTHOR]

Weakly nonlocal (WNL) Quantum Field Theories (QFTs) may define a new class of UV-completions in particle physics and gravity, without introducing any new elementary particle. One problematic issue is how to realize spontaneous symmetry breaking without introducing an infinite tower of ghosts in the perturbative spectrum. In this article, a WNL extension of the Standard Model (SM) is proposed: the Fuzzy Standard Model (FSM). It is a smooth deformation of the SM based on covariant star-products of fields. This new formalism realizes electroweak symmetry breaking without ghosts at tree-level. We give evidence that the FSM exhibits Vainshtein screening, aka classicalization, in the deep-UV. This could solve the electroweak hierarchy problem if it occurs at the TeV-scale. [ABSTRACT FROM AUTHOR]

A partial-wave analysis (PWA) for the photoproduction of pseudoscalar mesons on a nucleon using truncation in total angular momentum j is discussed. A formalism is described that can be used for investigating discrete ambiguities. Considerable attention is devoted to the connection of this type of PWA with that based on the truncation in orbital angular momentum l. [ABSTRACT FROM AUTHOR]

We report new pion electroproduction measurements in the Δ (1232) resonance, utilizing the SHMS - HMS magnetic spectrometers of Hall C at Jefferson Lab. The data focus on a region that exhibits a strong and rapidly changing interplay of the mesonic cloud and quark-gluon dynamics in the nucleon. The results are in reasonable agreement with models that employ pion cloud effects and chiral effective field theory calculations, but at the same time they suggest that an improvement is required to the theoretical calculations and provide valuable input that will allow their refinements. The data illustrate the potential of the magnetic spectrometers setup in Hall C towards the study the Δ (1232) resonance. These first reported results will be followed by a series of measurements in Hall C, that will expand the studies of the Δ (1232) resonance offering a high precision insight within a wide kinematic range from low to high momentum transfers. [ABSTRACT FROM AUTHOR]

Taking into account the recent parameterizations of parton distribution functions (PDFs), the momentum transfer dependence of generalized parton distributions (GPDs) of nucleons is obtained in the limit . The gravitational quark and gluon form factors of nucleons are calculated. It is shown that the gluon gravitational radius of the nucleon is comparable to the electromagnetic radius of the proton. The power dependence of form factors is investigated. As a result, it was obtained that the quark gravitational form factor is reproduced by the dipole form, while the form of the gluon gravitation form factor corresponds to the triple form. [ABSTRACT FROM AUTHOR]

Advantages of the amplitude method for the vector-meson-production description in respect of the spin-density-matrix-element (SDME) method are discussed. It is shown that for any nonzero amplitudes the angular distribution of final particles is non-negative. The exact formula for in terms of the SDMEs for spinless targets and the new approximate formula for nucleons are presented. [ABSTRACT FROM AUTHOR]

The deuteron beam vector polarization was obtained at the Nuclotron Internal Target Station using the proton–proton quasielastic scattering on the polyethylene target at the beam energies of 200, 500, 550, and 650 MeV/nucleon. The selection of useful events was performed using the time and amplitude information from the scintillation counters. The asymmetry on hydrogen was obtained by the subtraction of the carbon background. The obtained values are compared with the data obtained using the deuteron–proton elastic scattering at the beam energy of 135 MeV/nucleon. [ABSTRACT FROM AUTHOR]

The ultra-high-energy cosmic ray (UHECR) puzzle is reviewed under the hints of a few basic results: clustering, anisotropy, asymmetry, bending, and composition changes with energies. We show how the lightest UHECR nuclei from the nearest AGN or Star-Burst sources, located inside a few Mpc Local Sheets, may explain, at best, the observed clustering of Hot Spots at tens EeV energy. Among the possible local extragalactic candidate sources, we derived the main contribution of very few galactic sources. These are located in the Local Sheet plane within a distance of a few Mpc, ejecting UHECR at a few tens of EeV energy. UHECR also shine at lower energies of several EeV, partially feeding the Auger dipole by LMC and possibly a few nearer galactic sources. For the very recent highest energy UHECR event, if a nucleon, it may be explained by a model based on the scattering of UHE ZeV neutrinos on low-mass relic neutrinos. Such scatterings are capable of correlating, via Z boson resonance, the most distant cosmic sources above the GZK bound with such an enigmatic UHECR event. Otherwise, these extreme events, if made by the heaviest composition, could originate from the largest bending trajectory of heaviest nuclei or from nearby sources, even galactic ones. In summary, the present lightest to heavy nuclei model UHECR from the Local Sheet could successfully correlate UHECR clustering with the nearest galaxies and AGN. Heavy UHECR may shine by being widely deflected from the Local Sheet or from past galactic, GRB, or SGR explosive ejection. [ABSTRACT FROM AUTHOR]

Ultra-high-energy cosmic rays (UHECRs) are extremely rare energetic particles of ordinary matter in the Universe, traveling astronomical distances before reaching the Earth's atmosphere. When primary cosmic rays interact with atmospheric nuclei, cascading extensive air showers (EASs) of secondary elementary particles are developed. Radio detectors have proven to be a reliable method for reconstructing the properties of EASs, such as the shower's axis, its energy, and its maximum ( X max ). This aids in understanding fundamental astrophysical phenomena, like active galactic nuclei and gamma-ray bursts. Concurrently, data science has become indispensable in UHECR research. By applying statistical, computational, and deep learning methods to both real-world and simulated radio data, researchers can extract insights and make predictions. We introduce a convolutional neural network (CNN) architecture designed to classify simulated air shower events as either being generated by protons or by iron nuclei. The classification achieved a stable test error of 10%, with Accuracy and F 1 scores of 0.9 and an MCC of 0.8. These metrics indicate strong prediction capability for UHECR's nuclear composition, based on data that can be gathered by detectors at the world's largest cosmic rays experiment on Earth, the Pierre Auger Observatory, which includes radio antennas, water Cherenkov detectors, and fluorescence telescopes. [ABSTRACT FROM AUTHOR]

The properties of isospin-asymmetric cold nuclear matter are studied in terms of the relativistic mean-field theory in which, besides the fields of σ, ω, and ρ mesons, and the isovector, Lorentz-scalar field of the δ-meson is also taken into account. The properties of purely nucleonic np matter are studied as a function of the baryon density nB and the asymmetry parameter α, as well as the properties of electrically neutral β-equilibrium npe μ matter as a function of the baryon density nB. For different values of nB and a, such characteristics of np matter as the energy per baryon, the specific energy owing to isospin asymmetry, the effective proton and neutron masses, and the specific binding energy, are determined. It is shown that the energy owing to the asymmetry for a fixed value of α is a monotonically increasing function of the baryon density nB. For npem matter, the effective proton and neutron masses M p e f f , M n e f f , the specific binding energy Ebind, the symmetry energy Esym, the quantitative fraction of protons Yp = np/nB are studied, as well as the average meson fields σ ~ , ω ~ , δ ~ , and ρ ~ as functions of the baryon density nB. [ABSTRACT FROM AUTHOR]

The effects of low-lying core(30S) and projectile(31Cl) excited states on the full-width half maxima(FWHM) of longitudinal momentum distribution(LMD) of core fragment and single proton breakup cross-section of 12C(31Cl,30S)X breakup reaction at 44 MeV/nucleon beam energy have been analyzed quantitatively for the stripping and diffraction dissociation reaction mechanisms. The calculations are carried out using standard MOMDIS code based on Glauber eikonal approximation. Our analysis shows that the inclusion of core and projectile excitation enhances the LMD width and suppresses the magnitude of the single proton breakup cross-section significantly. Additionally, in comparison with the experimental LMD width, the contribution of s and d-state in admixed sd-state have also been explored. The obtained results are informative for the lucid structural study of the 31Cl nucleus. [ABSTRACT FROM AUTHOR]

Whether there exist elementary particles having Majorana nature is a fundamental open question that has persisted since the 1930s. The only practical experiments to test the Majorana nature of neutrinos is the search for neutrinoless double-beta decay, which has been a major challenge for nuclear and particle physicists. In the 2000s, a number of experiments using advanced technologies were planned, some of which have already achieved significant improvements in the search sensitivity. In this article, the current status of the neutrinoless double-beta decay searches is summarized, reviewing the progress of KamLAND-Zen, which recorded the world's best sensitivity in the effective Majorana neutrino mass limit. [ABSTRACT FROM AUTHOR]

In this paper, we utilize the effective Lagrangian method within the tree-level Born approximation to explore ϕ -meson photoproduction, i.e. γ p → ϕ p. Our analysis encompasses contributions from various sources, including the Pomeron, f 1 -Regge, pseudoscalar particles (π , η), scalar particles ( a 0 , f 0 ), protons, and three-nucleon resonance states. In addition, we consider a possible pentaquark-like K ∗ Σ -bound state P s . The findings indicate that, apart from the region near the threshold, contributions other than the Pomeron generally have a limited impact on the total cross-section. However, alternative contributions become crucial at specific angles, particularly at smaller values of cos θ. The incorporation of P s and other nucleon resonances proves essential to elucidate the bump observed near W ∼ 2. 1 5 GeV at very forward angles and behaviors within the range of W = (2. 0 − 2. 3) GeV. Furthermore, in the region with W ≥ 2. 5 GeV, where nucleon resonances become negligible, contributions from the t-channel mesons become pivotal. Our calculations for spin density matrix components, examined in various frames, exhibit improvement when considering all contributions. This comprehensive approach successfully reproduces the observed bump by including P s . We also briefly estimate the P s production via ϕ -meson photoproduction in the future Electron-Ion Collider (EIC), resulting in the luminosity of 10 fb − 1 per month. [ABSTRACT FROM AUTHOR]

Electromagnetic polarizabilities are fundamental properties of the proton that characterize its response to an external electromagnetic (EM) field. The generalization of the EM polarizabilities to non-zero four-momentum transfer opens up a powerful path to study the internal structure of the proton. They map out the spatial distribution of the polarization densities in the proton, provide access to key dynamical mechanisms that contribute to the electric and magnetic polarizability effects, and allow for the determination of fundamental characteristics of the system, such as the electric and magnetic polarizability radii. This article reviews our knowledge about proton EM generalized polarizabilities (GPs). An introduction is given to the basic concepts and the theoretical framework, which is then followed by a discussion that emphasizes the recent developments and findings of the virtual Compton scattering (VCS) experiments and future perspectives on the topic. [ABSTRACT FROM AUTHOR]

Peter Higgs was a British theoretical physicist, renowned for his 1964 work in which he proposed a mechanism capable of generating masses for elementary particles while conforming to gauge symmetry. Half a century later, two experiments at CERN confirmed that this mechanism is realized in nature. On April 8th, we received the sad news of the passing of this great pioneer in elementary particle physics. This article is dedicated to his memory, and to the mechanism and particle that bear his name. [ABSTRACT FROM AUTHOR]

Chirality is a phenomenon with widespread relevance in fundamental physics, material science, chemistry, optics, and spectroscopy. In this work, we show that a free electron can be converted by the field cycles of laser light into a right-handed or left-handed coil of mass and charge. In contrast to phase-vortex beams, our electrons maintained a flat de Broglie wave but obtained their chirality from the shape of their expectation value in space and time. Measurements of wave function densities by attosecond gating revealed the three-dimensional shape of coils and double coils with left-handed or right-handed pitch. Engineered elementary particles with such or related chiral geometries should be useful for applications in chiral sensing, free-electron quantum optics, particle physics or electron microscopy. [ABSTRACT FROM AUTHOR]

This article provides an overview of the European participation in the construction of the Electron Ion Collider (EIC), a significant project in nuclear physics. The EIC aims to study the structure of nucleons and nuclei by colliding highly polarized electrons with high-energy beams. The European community is actively involved in the project, with recommendations from the Nuclear Physics European Collaboration Committee (NuPECC) emphasizing European participation. European institutions are also contributing to the design and construction of the ePIC detector for the EIC experiment. The article emphasizes the importance of the EIC in advancing our understanding of the fundamental building blocks of matter and highlights the collaborative efforts of scientists from around the world. The European nuclear science community sees the EIC as an opportunity for further advancements in this field. [Extracted from the article]

The article discusses the dead-cone effect in quantum chromodynamics (QCD), which is a fundamental feature of the strong force that binds quarks and gluons together. The dead-cone effect refers to a region around the direction of flight of a parton where gluons cannot be emitted. The article explains how the dead-cone effect has been observed experimentally in the context of charm quarks and how it plays a role in the energy loss of charm and beauty quarks in the quark-gluon plasma. The article also discusses the ALICE experiment at the Large Hadron Collider (LHC) and its program to study the properties of the quark-gluon plasma. The article concludes by highlighting the importance of further measurements to better understand the energy loss experienced by quarks in the quark-gluon plasma. [Extracted from the article]

Nucleon–nucleon short range correlations (SRCs) in nuclei are important part of the nuclear structure and have been a subject of intensive studies in the last years. These objects represent temporary fluctuations in average nuclear matter density that occur when two or more nucleons separated by about 1 fm = 10–13 cm. Inspired by recent theoretical and experimental progress in understanding of SRC we reanalyzed our data on the production of high momentum and mesons emitted from nuclear targets irradiated by a proton beam. One of the basic properties of SRCs is the universality which means that they are equally involved in the creation of different hadrons on different nuclei, reflecting the properties of nuclear matter. So far, the property of universality has been observed in electron–nuclear collisions for the breakup of proton–neutron correlations, as well as in proton–nuclear collisions for the production of cumulative pions with high momenta. Both processes involve only light quarks. In this letter, we report the first observation of SRC universality in kaon production on nuclei in the kinematic region of high energy–momentum transfers thereby extending the investigation of the SRC universality to the sector of strange quarks. [ABSTRACT FROM AUTHOR]

Fourteen models are calculated with the shock velocity ranging from 200 to 330 km s |$^{-1}$| and pre-shock hydrogen nucleon density ranging from |$2.5\times 10^{12}$| to |$4\times 10^{13}$| cm |$^{-3}$|⁠. Among them the summed emergent flux of all spectral lines accounts for about 0.1–0.3 of the total veiling flux. The hydrogen Balmer continuum accounts for 0.17–0.1, while a nearly constant fraction close to 0.5 comes from emission produced by the stellar atmosphere. The main results derived from the veiling continuum energy distributions are two strong correlations: (1) the Balmer jump (BJ) increases as F K, the shock kinetic energy flux, decreases; and (2) at a fixed fraction of surface coverage by accretion shocks |$r_{\lambda }$|⁠ , the ratio of veiling to photospheric continuum flux at wavelength λ decreases as F K decreases. Using the BJ– F K and |$r_{4500\,\mathring{\rm A}}$| – F K relations, the observed excess continua of 10 T Tauri stars are modelled. For BP Tau and 3 Orion stars our accretion luminosities are higher than published values by a factor of a few. For the six Chamaeleon I stars, our observed accretion luminosities are about 27–78 per cent higher than corresponding published values. Comparison of model results on the He  i λ5876 Å flux with observed data indicates that, while those stars with dominant λ5876 Å narrow components can be readily accounted for by the calculated models, those with much stronger broad components cannot, and suggests that for the latter objects the bulk of their excess continua at 5876 Å do not originate from accretion shocks. [ABSTRACT FROM AUTHOR]

We generalize the U(1) gauge transformations of electrodynamics by means of an analytical extension of their parameter space and observe that this leads naturally to two gauge potentials, one electric, one magnetic, which permit the writing of local Lagrangians describing elementary particles with electric and magnetic charges. Gauge invariance requires a conformal transformation of the metric tensor. We apply this approach, which borrows from Utiyama's methodology, to a model with a massless scalar field and a model with a massless spinor field. We observed that for spinor models non-symmetrized Lagrangians can enable the existence of magnetic monopoles, but this is not possible with symmetrized Lagrangian. Such restrictions do not occur for spinless fields, but the model does not allow spin-one fields interacting with monopoles. [ABSTRACT FROM AUTHOR]

Ultrarelativistic nuclear collisions create a strongly interacting state of hot and dense quark–gluon matter that exhibits a remarkable collective flow behavior with minimal viscous dissipation. To gain deeper insights into its intrinsic nature and fundamental degrees of freedom, we determine the speed of sound in an extended volume of quark–gluon plasma using lead–lead (PbPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data were recorded by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 0.607 nb−1. The measurement is performed by studying the multiplicity dependence of the average transverse momentum of charged particles emitted in head-on PbPb collisions. Our findings reveal that the speed of sound in this matter is nearly half the speed of light, with a squared value of 0.241 ± 0.002 (stat) ± 0.016 (syst) in natural units. The effective medium temperature, estimated using the mean transverse momentum, is 219 ± 8 (syst) MeV . The measured squared speed of sound at this temperature aligns precisely with predictions from lattice quantum chromodynamic (QCD) calculations. This result provides a stringent constraint on the equation of state of the created medium and direct evidence for a deconfined QCD phase being attained in relativistic nuclear collisions. [ABSTRACT FROM AUTHOR]

In this section of Resonance, we invite readers to pose questions likely to be raised in a classroom situation. We may suggest strategies for dealing with them, or invite responses, or both. "Classroom" is equally a forum for raising broader issues and sharing personal experiences and viewpoints on matters related to teaching and learning science. G Gamow's alpha-decay theory (1928) is somewhat ad hoc for the reason that an alpha-particle inside a radioactive nucleus is supposed to move back and forth, through the dense mass of nucleons (retaining its identity), a number of times before it comes out. This short paper attempts to address this shortcoming via nuclear disintegration. [ABSTRACT FROM AUTHOR]

Main cosmic rays exceeding energy of approximately 100 TeV are examined via the cascade of particles in the EASs. Any explanation of these particles requires a thorough understanding of the shape of the spectrum and the variations in the overall structure of cosmic rays. The interaction of elementary particles with the nuclei of air atoms inside the atmosphere produces huge amounts of charged particles. To characterize an energy spectrum features of cascade particles, a total number of elementary particles such as electrons, muons, pions and nuclei of iron atoms within the energy range (1014-1018) eV was calculated using MATLAB program. The theoretical results were compared with experimental measurements, which showed a decent compatibility of muon - electron within the range of energies mentioned above. [ABSTRACT FROM AUTHOR]