The European Physical Journal C最新文献

We analyze the tree-level generation of entanglement through some key scattering processes in massless quantum electrodynamics on canonical noncomutative spacetime with space-space type of noncommutativity. The fermions in the noncommutative theory will be zero charge fermions. The scattering processes we shall study do not occur in ordinary Minkowski spacetime. We shall use the concurrence to characterize the amount of entanglement generated through a given scattering process. We shall show that, at tree-level, the concurrence for the scattering of two photons of opposite helicity is given by the same expression as in the case of the scattering of gluons in ordinary Minkowski spacetime. Thus, maximal entanglement is achieved if and only if the polar scattering angle is equal to (pi /2). We also compute the concurrence for the head-on collision in the laboratory reference frame of two fermions of opposite helicity to obtain the same result as in the case of photon scattering. Finally, we shall study a type of collision at right angles in the laboratory frame of fermions with opposite helicity. We show that in the latter case the concurrence depends on energy of the incoming fermions, the noncommutativity matrix (theta ^{ij}), the polar, (theta ), and azimuth angle, (phi ), of the zero-momentum frame of the incoming fermions. In this latter case we see that when (theta =pi /2) there are values of (phi ) for which no entanglement is generated.

The measurement of (Sigma ^{+}) production in pp collisions at (sqrt{s}=13) TeV is presented. The measurement is performed at midrapidity in both minimum-bias and high-multiplicity pp collisions at (sqrt{s} =13) TeV. The (Sigma ^{+}) is reconstructed via its weak-decay topology in the decay channel (Sigma ^{+} rightarrow mathrm{{p}} + pi ^{0}) with (pi ^{0} rightarrow gamma + gamma .) In a novel approach, the neutral pion is reconstructed by combining photons that convert in the detector material with photons measured in the calorimeters. The transverse-momentum ((p_{textrm{T}})) distributions of the (Sigma ^{+}) and its rapidity densities ({textrm{d}}N)/({textrm{d}}y) in both event classes are reported. The (p_{textrm{T}}) spectrum in minimum-bias collisions is compared to QCD-inspired event generators. The ratio of (Sigma ^{+}) to previously measured (Lambda ) baryons is in good agreement with calculations from the Statistical Hadronization Model. The high efficiency and purity of the novel reconstruction method for (Sigma ^{+}) presented here will enable future studies of the interaction of (Sigma ^{+}) with protons in the context of femtoscopic measurements, which could be crucial for understanding the equation of state of neutron stars.

Pulsars convert a significant fraction of their total spin-down power into very high-energy electrons, leading to the formation of TeV halos. While these halos are well characterized at TeV energies, it remains unclear whether pulsars also accelerate electrons efficiently at lower energies and how these particles propagate through their surrounding environments. We aim to test whether synchrotron emission from (sim 50)–(300 , textrm{GeV}) electrons around the Geminga pulsar can be detected in the frequency range observed by the Planck satellite. This would help constrain low-energy particle acceleration and diffusion in the vicinity of pulsars. We model the expected synchrotron emission from Geminga’s TeV halo based on various diffusion and injection spectrum scenarios and compare these predictions to publicly available multi-frequency Planck data. We find no conclusive evidence of spatially extended synchrotron emission associated with Geminga in any of Planck’s frequency bands. Our calculations show that even under favorable diffusion and injection conditions, the predicted synchrotron flux lies well below Planck’s measured background levels.

Hidden-charm pentaquark states with double strangeness, (P_{css}), have been predicted within the framework of unitary coupled-channel dynamics. In this work, we theoretically investigate the potential to observe these states in the decays (Lambda _brightarrow J/psi Xi ^-K^+) and (Xi _brightarrow J/psi Xi ^-pi ^+). In this framework, these pentaquark configurations couple strongly to the (J/psi Xi ) channel, as well as to other vector-baryon channels with the (bar{c} c s s n) flavor structure, making these decay modes promising for their observation through the corresponding invariant-mass distributions. Our analysis begins with the identification of the dominant weak decay mechanisms, followed by hadronization into meson-baryon channels, connected through flavor symmetry. Final-state interactions are then incorporated to dynamically generate the full amplitude, accounting for the formation of the pentaquark states. We compare our results with recent LHCb measurements of the (J/psi Xi ^-) mass distribution and find that, given the predicted pentaquark width of about 10 MeV in this channel, the state is too narrow to be resolved with the current experimental resolution, but it would become visible with significantly improved mass precision.

We introduce a new methodology to characterize properties of quantum spacetime in a strongly quantum-fluctuating regime, using tools from topological data analysis. Starting from a microscopic quantum geometry, generated nonperturbatively in terms of dynamical triangulations (DT), we compute the Betti numbers of a sequence of coarse-grained versions of the geometry as a function of the coarse-graining scale, yielding a characteristic “topological finger print”. We successfully implement this methodology in Lorentzian and Euclidean 2D quantum gravity, defined via lattice quantum gravity based on causal and Euclidean DT, yielding different results. Effective topology also enables us to formulate necessary conditions for the recovery of spacetime symmetries in a classical limit.

We perform a systematic analysis of the (Lambda _b rightarrow Lambda ) transition form factors using the perturbative QCD (PQCD) approach, taking into account contributions from higher-twist light-cone distribution amplitudes (LCDAs). Using inputs from lattice QCD, we show that the baryon higher-twist LCDAs give numerically dominant contributions to the form factors. By combining our PQCD results at low-(q^2) region with lattice QCD predictions at high (q^2,) we carry out z-series expansion fits to obtain a unified description of the form factors over the full physical kinematic range. We also provide predictions for physical observables in the rare decay (Lambda _b rightarrow Lambda mu ^+ mu ^-,) such as the differential branching fraction, the longitudinal polarization fraction of the dimuon system, and the forward–backward asymmetries.

The spin-curvature coupling in the Mathisson–Papapetrou–Dixon (MPD) formalism induces non-geodesic motion, shifting the orbital parameters of spinning test particles in black hole spacetimes. We investigate whether these quantitative shifts alter the qualitative, global structure of the orbit manifold. Using a topological approach, we study timelike circular orbits (TCOs) for spinning particles in static, spherically symmetric spacetimes. By constructing an auxiliary vector field, we compute the topological winding number W in horizon-bounded regions of asymptotically flat, anti-de Sitter (AdS), and de Sitter (dS) backgrounds. We find that W is robust against both the magnitude and direction of the particle’s spin: between two horizons, (W = -1,) guaranteeing at least one unstable TCO; outside the outermost horizon in asymptotically flat and AdS spacetimes, (W = 0,) enforcing that TCOs must appear in stable–unstable pairs or be absent. This spin independence reveals that the fundamental orbital structure is a property of spacetime geometry itself, not of the particle’s spin. We validate this with quantitative examples in Schwarzschild, Schwarzschild–AdS, and Schwarzschild–dS spacetimes, showing explicit spin-induced TCO shifts while confirming the invariant topology. This result provides a topological foundation for interpreting gravitational waveforms from extreme mass-ratio inspirals involving spinning secondaries.

In this study, we investigate the thermodynamic stability and geometric thermodynamics of the regular Bardeen-AdS black hole within the framework of Kaniadakis statistics, incorporating the (kappa )-deformed entropy. By varying both the Kaniadakis parameter (kappa ) and the black hole parameters, we uncover additional (kappa )-dependent thermodynamic branches, singularities, and divergence points that are absent in the standard ((kappa = 0)) case. The physical relevance of these new features is confirmed through geometric thermodynamics: curvature scalars computed from both the Quevedo geometrothermodynamic (GTD) and HPEM metrics precisely coincide with the phase transition points and divergence points identified from heat capacity and free energy analyses. Furthermore, the equation of state in the pressure-horizon radius plane reveals (kappa )-dependent critical behavior, consistent with the extended phase space analysis. The complete agreement among canonical, extended, and geometric thermodynamic diagnostics demonstrates that the (kappa )-induced branches correspond to physically distinct phases, providing a robust, (kappa )-dependent extension of the thermodynamic and phase structure of the Bardeen-AdS black hole.

We study symmetric and asymmetric cumulants as well as rapidity-even dipolar flow in ({}^{16})O+({}^{16})O collisions at (sqrt{s_{NN}} = 200) GeV to explore (alpha )-clustering phenomena in light nuclei within the viscous relativistic hydrodynamics framework. Signatures of (alpha )-clustering manifest in the anisotropic flow coefficients and their correlations – particularly in observables involving elliptic-triangular flow correlations. We show that final-state symmetric and asymmetric cumulants – especially (textrm{NSC}(2,3)) and (textrm{NAC}_{2,1}(2,3)) – are sensitive to the initial nuclear geometry. Additionally, we observe a significant difference in rapidity-even dipolar flow, (v_1^{text {even}}), between (alpha )-clustered and Woods–Saxon configurations in high-multiplicity events. These findings underscore the pivotal role of nuclear structure in heavy-ion collision dynamics and provide observables for distinguishing nuclear geometries, particularly in ultra-central collisions.

This paper investigates the shadow and quasinormal modes (QNMs) of a Schwarzschild black hole (BH) embedded in a Hernquist dark matter (DM) halo, focusing on the influence of DM parameters – specifically the core radius (r_{s}) and core density (rho _{s}) – on BH observational signatures. We analyze the structure of the BH shadow, lensing ring, and photon ring, showing that the shadow radius increases with both (r_{s}) and (rho _{s}). Using the WKB approximation, Padé approximants, and time-domain integration, we compute the QNMs for scalar, electromagnetic, and axial gravitational perturbations. Our results reveal that the DM halo modifies the spacetime’s effective potential: larger values of (r_{s}) or (rho _{s}) reduce the peak of the potential barrier, leading to lower oscillation frequencies and slower wavefunction damping. These findings highlight the systematic impact of DM on strong-field observables and suggest that BH shadows and QNMs provide a viable means to probe DM profiles in galactic nuclei.