The European Physical Journal A最新文献

We study the Gerasimov–Drell–Hearn (GDH) sum rule within a dynamical coupled-channel approach, the Jülich–Bonn model for light baryon resonances based on fits to an extensive data base of pion and photon induced data. Recently published photoproduction data for different observables with (pi N) and (eta N) final states are analyzed simultaneously with older data for the reactions (pi Nrightarrow pi N), (eta N), (KLambda ), (KSigma ) and (gamma prightarrow pi N), (eta N), (KLambda ), (KSigma ). The impact of the new data on the resonance spectrum is investigated and the contribution of the individual channels to the GDH integral is determined.

We obtain improved bounds on both the flavor-independent and -dependent vector interactions in a (2+1)-flavor Nambu-Jona-Lasinio (NJL) model using the latest precise LQCD results of the curvature coefficients of the chiral crossover line. We find that these lattice estimated curvature coefficients allow for both attractive and repulsive types of interactions in both the cases. With this constrained ranges of vector interactions, we further predict the behavior of the second ((kappa _2^B)) and fourth ((kappa _4^B)) order curvature coefficients as a function of the strangeness chemical potential ((mu _S)). We observe that the flavor mixing effects, arising from the flavor-independent vector interaction as well as from the ’t Hooft interaction, play an important role in (k_2^B). We propose that the mixing effects due to the vector interaction can be separated from those arising from the ’t Hooft interaction by analyzing the behavior of (k_2^B) as a function of (mu _S). Finally, we locate the critical endpoint in the (T-mu _B) plane using the model-estimated ranges of vector interactions and find the model’s predictions to be consistent with the latest LQCD bounds.

We have extended MadGraph5_aMC@NLO capabilities by implementing computations for asymmetric hadron-hadron collisions, including proton-nucleus, pion-hadron or nucleus-nucleus collisions in order to obtain a tool for automated perturbative computations of cross sections (or ratios of cross sections) in asymmetric reactions at next-to-leading (NLO) order in (alpha _S) in collinear factorisation. This tool, like the original symmetric version of MadGraph5_aMC@NLO, automatically computes cross sections for different factorisation and renormalisation scales and PDFs provided by the LHAPDF library, thereby allowing for an easy assessment of the associated theoretical uncertainties. In this paper, we present the validation of our code using W and Z boson production in pPb collisions and Drell-Yan-pair production in (pi W) collisions. We also illustrate the capabilities of the framework by providing cross section and nuclear modification factors with their uncertainties for the production of W and Z bosons, charm and bottom quarks as well as associated production of (b{bar{b}}+H^0) in pPb collisions at the LHC.

This work is dedicated to Angela Bracco in recognition of her contributions to the study of the Pygmy Dipole Resonance (PDR) using isoscalar probes. This approach is feasible due to the inherent isospin mixing of PDR states. In these cases, the key observable is the inelastic cross section. This article provides a brief review of such measurements and the corresponding calculations performed using a semiclassical model.

To investigate the energy dependence of the neutron capture cross section on ⁶⁸Zn close to the inelastic scattering threshold, we measured the ⁶⁸Zn((textit{n,}{gamma }))⁶⁹(textrm{Zn}^{{ m}}) reaction cross section at 1.12 ± 0.11, 1.40 ± 0.11, 1.62 ± 0.10 and 2.42 ± 0.09 MeV using the ⁷Li(p,n)⁷Be reaction as neutron source. The spectrum averaged neutron energy was computed using the neutron energy spectrum code EPEN and the neutron flux was normalized using the ¹¹⁵In(n,n’)¹¹⁵(textrm{In}^{{ m}}) monitor reaction. The data analysis was carried out using the latest decay data. Necessary corrections have been made for the low energy background neutron contribution and (gamma )-ray self-attenuation. After performing detailed uncertainty propagation, the newly measured cross sections are compared to previously published data found in the EXFOR database as well as to theoretical model predictions using TALYS-2.0 with different level density models and (gamma )-ray strength functions, and also with the most recent nuclear data evaluations, JENDL-5, ENDF/B-VIII.1, and JEFF-4.0. The present work significantly reduces the uncertainty to 6% compared to previously reported values ranging from 11% to 19%.

We study the g-mode non-radial oscillations of proto-neutron stars during the cooling stage. Based on finite-temperature extended Brueckner–Hartree–Fock theory and the relativistic mean-field theory, and combined with appropriate crust equations of state, we construct isentropic equations of state for proto-neutron stars with neutrino trapping. Under the frozen-fluid assumption during oscillations, the difference between the adiabatic and equilibrium sound speeds gives rise to nonzero Brunt–Väisälä frequencies, which enables the existence of g-mode oscillations. We then study the effects of temperature and neutrino trapping on the g-mode frequencies under the Cowling approximation, making comparisons between results with the two EOSs and examining the impact of varying crust equations of state. Our results show that, compared with cold neutron stars, neutrino trapping significantly reduces gravity-mode frequencies in both models, and the relativistic mean-field model systematically yields lower frequencies than the Brueckner–Hartree–Fock model. Neutrino trapping also prolongs gravitational wave damping times and reduces the strain amplitudes, but predictions indicate that the signals remain within the sensitivity of current and future detectors. These findings highlight the potential of gravitational wave observations to probe the interior physics of proto-neutron stars.

We evaluate for the first time the (eta ^prime p) femtoscopic correlation function to study the (eta ^prime N) interaction. We find it extremely sensitive to the value of the (eta ^prime p) scattering length, for which at present there exists only very limited information, not even knowing its sign. The measurement of this correlation function would provide much valuable information on the (eta ^prime N) interaction, which could then also be used to settle the issue of possible (eta ^prime ) nucleus bound states, an issue attracting much attention in the nuclear physics community.

Neutron inelastic scattering on (^{19}hbox {F}) was studied via prompt-(gamma )-ray spectroscopy with an array of high-purity germanium detectors at the GELINA neutron time-of-flight (TOF) facility. Seven (gamma )-ray production cross sections were measured, normalised to the (^{235})U(n, f) cross section standard. In addition, the total inelastic scattering cross section and direct population cross sections of the first six excited states were determined, all from reaction threshold up to 18 MeV incident neutron energy. Comparisons with previous experimental and evaluated data reveal significant disagreements.

For the first time, the flux-weighted average yields were measured of both the ¹³⁵Ba(γ,p)¹³⁴Cs^m+g and ¹³⁷Ba(γ,p)¹³⁶Cs^m+g reactions at E_br = 19 MeV, and the ¹⁴³Nd(γ,p)¹⁴²Pr^m+g reaction at E_br = 19 and 19.5 MeV. The measured flux-weighted average yields of the ¹³⁴Ba(γ,n)¹³³Ba^m+g and ¹⁴⁸Nd(γ,n)¹⁴⁷Nd reactions coincided with the results of the works of other authors and with the results of simulations within the TALYS-1.96 code. At the same time, for the (γ,p)-reactions in this code, it was not possible to achieve agreement between theoretical and experimental results. It seems this has been achieved by taking into account the isospin splitting of the GDR with shell corrections within semidirect mechanism.