The European Physical Journal C最新文献

We improve the perturbative QCD (PQCD) formalism for multi-body charmless hadronic B meson decays, such as (Brightarrow VP_3 rightarrow P_1P_2P_3), by resolving the possible discrepancy in parametrizing the contribution of the P-wave resonance V to the two-meson distribution amplitudes (DAs) associated with the pairs (P_1P_2=pi pi , Kpi , KK). The determination of the Gegenbauer moments in the two-meson DAs is then updated in the global fit of the improved PQCD factorization formulas at leading order in the strong coupling (alpha _s) to available data for branching ratios and polarization fractions of three- and four-body B decays. The convergence of the Gegenbauer expansion of the resultant two-meson DAs is manifest. The satisfactory quality of the fit implies the consistency of the PQCD framework for multi-body B decays and the universality of the nonperturbative two-meson DAs. In particular, the predicted longitudinal polarization fraction (f_0(B_s^0rightarrow K^{*0} {bar{K}}^{*0})=28.2^{+8.8}_{-9.5} %) with the updated Gegenbauer moments matches well the measurement. The observable (L_{K^{*0}{bar{K}}^{*0}}=7.7^{+4.9}_{-3.8}), defined as the ratio of the longitudinal amplitudes of the two U-spin related channels (B_s^0rightarrow K^{*0} {bar{K}}^{*0}) and (B^0rightarrow K^{*0} {bar{K}}^{*0}), accommodates the current data within errors. It is found that the direct CP asymmetries ({{mathcal {A}}}^{0,||,bot }_{textrm{CP}}) in the polarization states of some four-body decays (Brightarrow V_1V_2rightarrow (P_1P_2)(P_3P_4)) might be large, but the destruction among them result in small net CP violation. Our predictions can be confronted with LHCb and Belle-II data in the future.

We apply general relativity in higher dimensions to the collapse of an unstable massive body. A general solution is obtained for the heat flux boundary condition in n-dimensions. The temporal function obtained is then used to complete the description of an unstable neutron star which collapses from an initial static configuration. A Finch–Skea ansatz together with a linear equation of state was used to obtain the static configuration which is a solution of the static field equations. It is found that the collapse time is reduced in higher dimensions. The energy densities generally increase with dimension, although they tend to coalesce at horizon formation. The surface heat flux also coalesces near horizon formation with extra dimensions reducing the heat flux.

The composition and equation of state (EoS) of dense matter relevant to compact stars are quite inconclusive. However, certain observational constraints on the structural properties of compact stars help us constrain the EoS to a fair extent. Moreover, gravitational asteroseismology gives a notion of the composition and EoS of compact stars. The next generation gravitational wave (GW) detectors are likely to detect several oscillation mode frequencies of the GWs. In this work we compute the fundamental (f) and the first pressure ((p_1)) mode frequencies ((f_f) and (f_{p1}), respectively) with different compositions viz., hadronic, quark, and hybrid star (HS) matter. For HSs, we also study the gravity (g) mode frequency ((f_g)). For each phase we also study the correlation between the oscillation frequencies of 1.4 (M_{odot }) and 2.01 (M_{odot }) compact stars with other different properties. We find that various possible composition of compact stars substantially affects the oscillation frequencies. However, the mass-scaled angular f mode frequency ((omega _f M)) varies universally with compactness (C) for all hadronic, quark and hybrid stars. The f mode frequency ((f_{f_{1.4}})) of the canonical 1.4 (M_{odot }) compact star, obtained with different composition, is quite correlated with the canonical radius ((R_{1.4})) and tidal deformability ((varLambda _{1.4})) while (f_{p_{1.4}}) is well correlated with slope parameter of the symmetry energy. We also show that (f_{g_{1.4}}) of the HSs varies almost linearly with (varLambda _{1.4}). Should g modes be detected, they could not only support the existence of HSs, but (f_g) could be useful to understand the strength of quark repulsion in HSs.

We examine a static spherically symmetric black hole metric that originates from the vacuum solution of the traceless metric-affine bumblebee model in which spontaneous Lorentz symmetry-breaking occurs when the bumblebee fields acquire a non-vanishing vacuum expectation value. A free Lorentz-violating parameter enters into the basic formulation of the metric-affine bumblebee model. In this study, we use observations from the Event Horizon Telescope (EHT) collaboration on (M87^*) and (SgrA^*) to analyse the shadow of the black hole and an attempt has been made to constrain that free Lorentz-violating parameter. We also investigate particle motion over time-like geodesics and compute the corresponding epicyclic frequencies. We further constrain the Lorentz-violating parameter by using the reported high-frequency quasi-periodic oscillations (QPOs) of microquasars, offering new insights into its possible impact on astrophysical phenomena.

In this work, we explore the implications of the Cohen and Glashow Very Special Relativity (VSR) theory, a framework that introduces Lorentz invariance violation through the presence of a preferred direction. Our analysis focuses on the impact of VSR on the Cherenkov angle, revealing modifications to the dispersion relation of particles, particularly the photon and the electron, which acquire an effective inertial mass. This modification also implies a deviation in the speed of light, which can be constrained through precise experimental measurements. Using data from the RICH system of the LHCb experiment, we take advantage of its capability to reconstruct Cherenkov angles within the momentum range of the particles of 2.6–100 GeV/c. These measurements, combined with the most stringent laboratory tests of the isotropy of the speed of light ((Delta c / c sim 10^{-17})), allow us to impose new upper bounds on the parameter (Omega ), which quantifies a deviation from the standard Special Relativity. Furthermore, we establish an analogy between VSR and Minkowski’s electrodynamics in a dielectric medium for particles with very high velocity, offering a physically intuitive interpretation of the parameter (Omega ).

Explicit example, where the Hawking temperature of a black hole horizon is compatible with the black hole’s Rényi entropy thermodynamic description, is constructed. It is shown that for every static, spherically symmetric, vacuum black hole space-time, a corresponding black hole solution can be derived, where the Hawking temperature is identical with the Rényi temperature, i.e. the one obtained from the Rényi entropy of the black hole via the 1st law of thermodynamics. In order to have this Hawking–Rényi type thermodynamic property, the black holes must be surrounded by an anisotropic fluid in the form of a Kiselev metric, where the properties of the fluid are uniquely determined by the mass of the black hole, M, and the Rényi parameter, (lambda ). In the simplest Schwarzschild scenario, the system is found to be thermodynamically unstable, and the 3rd law of thermodynamics seems to play the role of a cosmic censor via placing an upper bound on the black hole’s mass, by which preventing the black hole from loosing its horizon(s).

The Taishan Antineutrino Observatory (TAO) is a liquid-scintillator satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO) to measure the reference reactor neutrino spectrum with unprecedented energy resolution. We use inhomogeneous Poisson process and Tweedie generalized linear model (GLM) to characterize the detector response and the charge distribution of a SiPM. We develop a pure probabilistic model for time and charge of SiPMs from first principles to reconstruct point-like events in the TAO central detector. Thanks to our precise model and the high photo-coverage and quantum efficiency of the SiPM tiles at TAO, we achieve vertex position resolution better than (20,hbox {mm}), energy resolution of about (2%) at (1,hbox {MeV}) and (<0.5%) non-uniformity, marking the world’s best performance of liquid scintillator detectors. With such resolution, we perceive (hbox {MeV}) events to exhibit track effects. It opens up an exciting possibility of computed tracking calorimeter for unsegmented liquid scintillator detector like TAO. Our methodology is applicable to other experiments that utilize PMTs for time and charge readouts.

We apply the Kosambi–Cartan–Chern theory to perform an extensive examination of Jacobi stability of geodesics around rotating black hole solutions to dynamical Chern–Simons gravity, a theory that introduces modifications to General Relativity via a scalar field non-minimally coupled to curvature scalars. We present a comparative study between Jacobi and Lyapunov stability, pointing out the advantages of the more geometrical method over the usual Lyapunov approach.

The detection of gravitational waves (GW) from astrophysical sources has opened a new era in physics. However, advances in high-energy laser systems make it possible to consider gravitational waves produced in the laboratory. In this work, the angular distribution and energy flux of gravitational waves radiated by high-power Laguerre–Gaussian beams are analysed. With a power of (10^{22}~text {W}/text {cm}^2) and frequency of (10^{15}) Hz for the LG beams, the radiated GW frequency is twice the laser frequency and the maximal GW amplitude can reach (10^{-34},) which is quite small compared with the current detection threshold of around (10^{-21}) by LIGO. It is shown in Ejlli et al. (Eur Phys J C 79:1032, 2019) that the inverse Gertsenshtein effect is able to detect ultra high frequency gravitational wave with frequency up to (10^{15}) Hz and strain around (10^{-30},) which may provide a viable way to measure gravitational waves produced by high-power lasers in the future.

We propose a method which allows the inclusion of exclusive heavy vector-meson production data at low x in future global parton analyses. As an example we perform a study within xFitter to determine the gluon parton distribution function (PDF) at next-to-leading order (NLO) at moderate-to-low x using the measurements of exclusive (J/psi ) production in ep and pp collisions from HERA and LHC. We further study the constraints from the corresponding (Upsilon ) production process. We finish by discussing the possible effects at next-to-next-to-leading order (NNLO) through incorporation of a K factor for the exclusive heavy vector-meson coefficient function at NLO.