The European Physical Journal C最新文献

The CYGNO experiment aims to build a large ((mathcal {O}(10)) m(^3)) directional detector for rare event searches, such as nuclear recoils (NRs) induced by dark matter (DM), such as weakly interactive massive particles (WIMPs). The detector concept comprises a time projection chamber (TPC), filled with a He:CF(_4) 60/40 scintillating gas mixture at room temperature and atmospheric pressure, equipped with an amplification stage made of a stack of three gas electron multipliers (GEMs) which are coupled to an optical readout. The latter consists in scientific CMOS (sCMOS) cameras and photomultipliers tubes (PMTs). The maximisation of the light yield of the amplification stage plays a major role in the determination of the energy threshold of the experiment. In this paper, we simulate the effect of the addition of a strong electric field below the last GEM plane on the GEM field structure and we experimentally test it by means of a 10 (times ) 10 cm(^2) readout area prototype. The experimental measurements analyse stacks of different GEMs and helium concentrations in the gas mixture combined with this extra electric field, studying their performances in terms of light yield, energy resolution and intrinsic diffusion. It is found that the use of this additional electric field permits large light yield increases without degrading intrinsic characteristics of the amplification stage with respect to the regular use of GEMs.

Motivated by the impact of the phantom field (or anti-Maxwell field) on the structure of three-dimensional black holes in the presence of the cosmological constant, we present the first extraction of solutions for the phantom BTZ (A)dS black hole. In this study, we analyze the effect of the phantom field on the horizon structure. Furthermore, we compare the BTZ black holes in the presence of both the phantom and Maxwell fields. Additionally, we calculate the conserved and thermodynamic quantities of the phantom BTZ black holes, demonstrating their compliance with the first law of thermodynamics. Subsequently, we assess the effects of the electrical charge and the cosmological constant on the local stability in the canonical ensemble by considering these fields with respect to the heat capacity. We then investigate the global stability area of the BTZ black holes with phantom and Maxwell fields within the grand canonical ensemble using Gibbs free energy. In this analysis, we evaluate the influence of the electrical charge and the cosmological constant on this area.

Coherent elastic neutrino-nucleus scattering (CE(nu )NS) poses an irreducible background in the search for dark matter-nucleus elastic scatterings, which is commonly known as the neutrino floor. As direct dark matter search experiments keep improving their sensitivity into so far unexplored regions, they face the challenge of approaching this neutrino floor. A precise description of the CE(nu )NS signal is therefore crucial for the description of backgrounds for future DM searches. In this work we discuss the scenario of detecting neutrinos in low-threshold, high-exposure cryogenic solid state experiments optimized for the search of low-mass dark matter. The energy range considered is completely dominated by solar neutrinos. In absence of any dark matter events, we treat solar neutrinos as the main signal of interest. We show that sensitivity to the flux of neutrinos from different production mechanisms can be achieved. In particular we investigate the sensitivity to the flux of pp and (^{7})Be neutrinos, as well as CNO neutrinos. Furthermore, we investigate the sensitivity to dark matter signals in the presence of a solar neutrino background for different experimental scenarios, which are defined by three parameters: the target material, the energy threshold and the exposure. We show that experiments with thresholds of (mathcal {O})(eV) and exposures of (mathcal {O})(tonne-years), using (hbox {CaWO}_{4}) or (hbox {Al}_{2}hbox {O}_{3}) targets, have discovery potential for dark matter interaction cross sections in the neutrino floor.

We study the anomalous magnetic moment of the muon, (g_mu - 2 equiv 2 a_mu ), in the context of supersymmetric models beyond the CMSSM, where the unification of either the gaugino masses (M_{1,2,3}) or sfermion and Higgs masses is relaxed, taking into account the measured mass of the Higgs boson, (m_H), the cosmological dark matter density and the direct detection rate. We find that the model with non-unified gaugino masses can make a contribution (Delta a_mu sim 20 times 10^{-10}) to the anomalous magnetic moment of the muon, for example if (M_{1,2} sim 600; textrm{GeV}) and (M_3sim 8 ; textrm{TeV}). The model with non-universal sfermion and Higgs masses can provide even larger (Delta a_mu sim 24 times 10^{-10}) if the sfermion masses for the first and the second generations are ( sim 400 ; textrm{GeV}) and that of the third is ( sim 8 ; textrm{TeV}). We discuss the prospects for collider searches for supersymmetric particles in specific benchmark scenarios illustrating these possibilities, focusing in particular on the prospects for detecting the lighter smuon and the lightest neutralino.

These lectures were presented at the 2024 QCD Masterclass in Saint-Jacut-de-la-Mer, France. They introduce and review fundamental theorems and principles of machine learning within the context of collider particle physics, focused on application to jet identification and discrimination. Numerous examples of binary discrimination in jet physics are studied in detail, including (Hrightarrow b{bar{b}}) identification in fixed-order perturbation theory, generic one- versus two-prong discrimination with parametric power counting techniques, and up versus down quark jet classification by assuming the central limit theorem, isospin conservation, and a convergent moment expansion of the single particle energy distribution. Quark versus gluon jet discrimination is considered in multiple contexts, from using additive, infrared and collinear safe observables, to using hadronic multiplicity, and to including measurements of the jet charge. While many of the results presented here are well known, some novel results are presented, the most prominent being a parametrized expression for the likelihood ratio of quark versus gluon discrimination for jets on which hadronic multiplicity and jet charge are simultaneously measured. End-of-lecture exercises are also provided.

The electron-positron pair (EPP) creation under Gaussian and super-Gaussian pulse trains are studied by the computational quantum field theory (CQFT) in the single-photon regime. The details of the EPP creation are studied from the time evolution of the EPP number, energy spectra and spatial distribution of the electrons. The results indicate that the final created EPPs is the non-linear accumulation of the multi-pulses, which depends on the time interval, pulse shape and pulse number. The optimal time interval can be chosen based on the pulse resonance condition, which is derived by the perturbation method. Besides, steeper super-Gaussian pulses and adding more pulses facilitate the EPP creation as well. The results indicate that, under optimal multi-pulse parameters, the number of the EPPs obtained is much larger than the sum of the EPPs created under the same number of single pulses. This finding not only can enhance the EPP creation, but also can improve the multi-pulse utilization and guide future experimental research on the EPP creation.

In this paper, we investigate the time dependent black holes in the frame of Einstein–Gauss–Bonnet theory having two scalar fields and investigate the propagation of the gravitational wave (GW). In the reconstructed models, there often appear ghosts, which could be eliminated by imposing some constraints. We investigate the behavior of high-frequency gravitational waves by examining the effects of varying Gauss–Bonnet coupling during their propagation. The speed of propagation changes due to the coupling during the black hole formation process. The propagation speed of gravitational waves differs when they enter the black hole compared to when they exit.

Testing possible variations in fundamental constants of nature is a crucial endeavor in observational cosmology. This paper investigates potential cosmological variations in the fine structure constant ((alpha )) through a non-parametric approach, using galaxy cluster observations as the primary cosmological probe. We employ two methodologies based on galaxy cluster gas mass fraction measurements derived from X-ray and Sunyaev–Zeldovich observations, along with luminosity distances from type Ia supernovae. We also explore how different values of the Hubble constant ((H_0)) impact the variation of (alpha ) across cosmic history. When using the Planck satellite’s (H_0) observations, a constant (alpha ) is ruled out at approximately the 3(sigma ) confidence level for (z lesssim 0.5). Conversely, employing local estimates of (H_0) restores agreement with a constant (alpha ).

Astrophysical fluids subjected to the strong gravity of black holes can form rotating toroidal-like structures known as thick accretion discs. In order to facilitate the study of such structures, we introduce approximate empirical formulae for a relatively simple analytical description of their poloidal cross-sections that are usually described only numerically. Our comparisons of the approximate and exact descriptions of the cross-sections of the structures rotating around Schwarzschild and Kerr central black holes, together with the determination of the associated total masses of these structure, indicate a high degree of accuracy for these introduced formulae.