The European Physical Journal C最新文献

We study an alternative (U(1)_{B-L}) model with singlet chiral fermions which can act as WIMP and FIMP type DM, which is anomaly-free by constructions in contrast to the well studied (B-L) extension where three right handed neutrinos are needed for gauge anomaly cancellation. Fermion dark matter masses are generated after the (U(1)_{B-L}) is broken spontaneously, so the Yukawa couplings for WIMP and FIMP components can be distinguished by the hierarchical values of the vacuum expectation values of the singlet scalar fields. Moreover, the (U(1)_{B-L}) gauge boson receives a TeV-scale mass for a tiny extra gauge coupling, so it goes out of equilibrium from the rest of the model content in the early Universe. Both the (U(1)_{B-L}) gauge boson and FIMP component are produced from the decays of the bath particles, and the former can decay into FIMP DM and/or WIMP DM before BBN. The WIMP component can reside in the resonance region of the Higgs bosons or dominantly annihilate into a pair of singlet-like scalars. Thus, there is a flexibility to choose a small mixing between the visible and dark sectors, thereby evading all the current direct and indirect detection bounds. Furthermore, we show that WIMP and FIMP components can coexist in suitable fractions, depending on the choice of model parameters, allowing for additional protection for WIMP DM against various experimental bounds. Finally, we identify the dimension-6 and dimension-7 operators for Majorana neutrino masses in our model, being consistent with the (U(1)_{B-L}) gauge symmetry, and provide a possibility of extending the model with additional singlet fermions for neutrino masses.

Thermodynamical topology has emerged as a powerful framework for classifying the thermodynamical behavior of black holes. Three distinct yet complementary topological invariants have been employed to characterize black hole phases, spinodal curves, and critical points in black hole thermodynamics. In this work, we develop a unified framework that integrates these three topological approaches and introduce the concept of extended thermodynamical topology, providing a clear physical interpretation. As a first step, we apply this framework to black holes in Einstein gravity, systematically elucidating their phase structure in terms of topological invariants. We then extend our analysis to black holes in 7-dimensional Lovelock gravity, where novel thermodynamic phenomena naturally emerge from the topological perspective. Moreover, we explore the connection between critical exponents and the extended thermodynamical topology, uncovering a correspondence between the zeros of the k-th order vector field and the associated critical exponents. Our study demonstrates that extended thermodynamical topology offers a robust and fine-grained framework for analyzing and classifying black hole phase transitions.

Some relevant aspects of a new form of generalized entropic cosmology, recently introduced by Nojiri, Odintsov and Faraoni, are considered. The setup is a logarithmic equation of state for a viscous dark fluid coupled with dark matter, in the ordinary Friedmann–Lemaître–Robertson–Walker flat universe. The influence of thermal effects, caused by Hawking radiation, near the singularity, are carefully investigated. In particular, their role on the formation and specific type of the Big Rip expected to occur within a finite time. It is shown that a scenario arises, where a qualitative change towards the good direction, in the type of the singularity formed, does occur. On top of that, another very interesting scenario is obtained, where the singularity vanishes completely.

This study investigates the performance of bent silicon crystals intended to channel hadrons in a fixed-target experiment at the Large Hadron Collider (LHC). The phenomenon of planar channelling in bent crystals enables extremely high effective bending fields for positively charged hadrons within compact volumes. Particles trapped in the potential well of high-purity, ordered atomic lattices follow the mechanical curvature of the crystal, resulting in macroscopic deflections. Although the bend angle remains constant across different momenta (i.e., the phenomenon is non-dispersive), the channelling acceptance and efficiency still depend on the particle momentum. Crystals with lengths in the range of 5 to 10 cm, bent to angles between 5 and 15 mrad, are under consideration for measurements of the electric and magnetic dipole moments of short-lived charmed baryons, such as the (varLambda _c^+). Such large deflection angles over short distances cannot be achieved using conventional magnets. The principle of inducing spin precession through bent crystals for magnetic dipole moment measurements was first demonstrated experimentally in the 1990s. Building on this concept, experimental layouts are now being explored for implementation at the LHC. The feasibility of such measurements depends, among other factors, on the availability of crystals that exhibit the required mechanical properties to reach the necessary channelling performance. To address this, a dedicated machine experiment – TWOCRYST – has been installed in the LHC to carry out beam tests in the TeV energy range. The bent crystals for TWOCRYST were fabricated and tested using both X-ray diffraction and high-momentum hadron beams at 180 GeV/c at the CERN Super Proton Synchrotron (SPS) extraction lines. Two crystals based on established technologies were included in this test. In addition, a crystal bent via anodic bonding was tested for the first time with high-energy hadrons to assess its potential for future accelerator applications. This paper presents an analysis of the performance of the three tested crystals and, where possible, outlines key differences in their properties attributed to the respective bending techniques.

Astrophysical evidence has hinted at the existence of a nonzero NUT charge, which breaks the (mathbb {Z}_2) symmetry of spacetime and induces novel features in geodesics. In this work, we investigate the Lense–Thirring precession of the spherical orbits in the Kerr–Taub–NUT spacetime, with particular emphasis on its connection to recent observations of black hole jet precession. We analyze the reflection symmetry breaking in trajectories of the spherical orbits and extract their precession angular velocity. It is worth noting that in the absence of spin, the spherical orbits reduce to tilted circular orbits without precession, whereas for nonzero spin, the precession angular velocity increases with the absolute value of the NUT charge. We then model the motion of particles near the warp radius of a tilted accretion disk using the spherical orbits and constrain the black hole parameter space based on the observed jet precession of M87*. The results indicate that regions with low spin and large NUT charge were excluded, and that the jet precession measurements cannot distinguish the sign of the NUT charge. The excluded region is larger for retrograde accretion disks than for prograde ones. We also find that this observation do not allow a clear distinction between black holes and naked singularities. Moreover, we also explore how black hole parameters influence the structure of accretion disk. These results have important theoretical and astronomical significance for us to deeply understand NUT space-time.

This study presents an analysis of seasonal variations in the atmospheric muon neutrino flux, using 11.3 years of data from the IceCube Neutrino Observatory. By leveraging a novel spectral unfolding method, we explore the energy range from 125 GeV to 10 TeV for zenith angles from ({90}^{circ }) to ({110}^{circ }), corresponding to the Antarctic atmosphere. Our findings reveal that the differential measurement of the amplitudes of the seasonal variation is consistent with an energy-dependent decrease reaching ((-,4.5) ± 1.2)% during Austral winter and increase to (+ 3.9 ± 1.3)% during Austral summer relative to the annual average at 10 TeV. While the unfolded flux exceeds the model predictions by up to 30%, the differential measurement of the seasonal to annual average flux remains unaffected. The measured seasonal variations of the muon neutrino spectrum are consistent with theoretical predictions using the MCEq code and the NRLMSISE-00 atmospheric model.

In this study, we investigate a nonlinear mechanism driving the formation of scalarized rotating black holes within a scalar-Gauss–Bonnet gravity framework that includes an additional squared Gauss–Bonnet term. With the specific coupling function, Kerr metric is a solution to this modified gravity. In linear level Kerr black holes are stable against the scalar perturbation, while nonlinearly they suffer the so-called “nonlinear scalarization” and are unstable. By employing a pseudo-spectral method, we derive the spectrum of nonlinearly scalarized rotating black hole solutions, revealing multiple scalarized branches. Our analysis demonstrates that both the black hole’s spin and the additional squared Gauss–Bonnet term significantly influence the existence and properties of these solutions. Furthermore, we explore the thermodynamic properties of nonlinearly scalarized rotating black holes, and find that the scalarized black holes are entropically favored over Kerr black holes of the same mass and spin across a wide range of parameters.

Applying the computational quantum field theory (CQFT), this study pioneers the implementation of oscillating Gaussian potential well as a tunable external field for manipulating boson pair creation from the vacuum. The potential well width crucially control the boson pair creation via photon resonance transition. Expanding of the width can lead to a shift in the resonance transition mode from double to single transition channels, governing two interesting quantum regimes: narrow potential well widths induce dual-channel transitions with spectral splitting (characteristic of the Autler–Townes effect), while wide width yields monochromatic single-peaks with high spectral purity. Besides, energy spectral peaks exhibit a quantitative correlation with well frequency, enabling targeted boson population modulation. Furthermore, steeper-edged super-Gaussian well enhance boson yield and broaden energy spectra compared to Gaussian potential well. Parametric control of oscillating Gaussian-type wells (via width/shape modulation) establishes a quantum pair-creation paradigm, while their selective tunability enables fundamental explorations in vacuum physics and experimental design.

In compact stellar environments, the stability of dense QCD matter requires the simultaneous fulfillment of charge neutrality and beta equilibrium. In this work, we study how temperature and finite chemical potential affect QCD topology and axion properties within this medium, analyzing both cases with and without the charge neutrality condition. Our results show that the topological susceptibility and axion properties are highly sensitive to the critical behavior of the chiral phase transition in both cases. In particular, the axion mass is strongly suppressed near the transition, while the axion self-coupling constant develops a pronounced peak whose magnitude depends on the temperature and density of the medium. Remarkably, around the critical point at (Tsimeq 70) MeV and (mu simeq 346) MeV, the self-coupling constant is enhanced by more than a factor of seven compared to its vacuum value, a feature that to the best of our knowledge has not been reported in previous studies. Such a strong amplification at the phase boundary indicates that axion-mediated interactions could play an important role in shaping the structure and stability of compact stars, with potential implications for their evolution and observable astrophysical signatures.

Inspired by the abundant structure near the threshold of the (D^{(*)}K^{(*)}/bar{D}^{(*)}K^{(*)},) we estimate the strong decay properties of the (T_{cbar{s}1}^{f/a}) and (T_{bar{c}bar{s}1}^{f/a}) with (I(J^{P})=0/1(1^{+})) in (DK^{*}) and (bar{D}K^{*}) molecular scenarios in the present paper. By employing the effective Lagrangian approach, the widths of the processes (T_{cbar{s}1}^{f}rightarrow D^{*}K, D_{s}^{*}eta , DKpi ,) (T_{cbar{s}1}^{a}rightarrow D^{*}K, D_{s}^{*}pi , DKpi ,) and (T_{bar{c}bar{s}1}^{f/a}rightarrow bar{D}^{*}K, bar{D}Kpi ) are estimated. Considering the present estimations, we propose to search for (T_{cbar{s}1}^{f/a}) states in (D^{*}K) and (D_{s}^{*}pi /D_{s}^{*}eta ) mass invariant spectra. Their ratios may serve as an important test of the molecular scenario.