The European Physical Journal A最新文献

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.

In this study, we investigate the extraction of the nonsinglet structure function, (xF_3(x, Q^2)), where the valence input densities are parameterized in terms of the Chebyshev polynomials. These polynomials provide an efficient basis for approximating functions, and using them in the analysis of structure functions allows for a compact and accurate representation. We then construct the Mellin-transformed of (xF_3(x, Q^2)) structure function where the nuclear effect is imposed on the parameterized valence densities. The Chebyshev polynomial approach provides an effective framework for the analysis of the nonsinglet structure function (xF_3(x, Q^2)), offering accurate and computationally efficient calculations. Using the Wilson coefficient and splitting functions available in the literature, the evolution of the moment of structure functions in Mellin space is done up to (hbox {N}^{3})LO accuracy. Transforming the structure function in Mellin space to the x-Bjorken space, is performed taking into account the Jacobi polynomials expansions. We compare our results with the results of some models and also the available experimental data for iron target and obtain good agreement with these findings. To further support our QCD analysis on valence densities, we calculate various sum rules such as Gross-Llewellyn-Smith (GLS), Bjorken unpolarized (Bup) and Bjorken polarized (Bp) sum rules, as well as the Adler sum rule. Our results align well with both the theoretical predictions and the available experimental data and also verify the connection between three GLS, Bup, and Bp sum rules.

An electron scattering experiment to search for the trineutron state ³n by reaction (mathrm{^4He}(e,~e'ppi ^{+})^{3}n) is designed for the A1 facility at Mainzer Microtron. The detailed principles, setup, and simulation of this experiment are presented. With the momenta of the scattered electron, the produced proton and (pi ^+) from the reaction measured by three spectrometers with their triple coincidence, the missing mass spectrum of ³n can be obtained. The production rate of ³n based on the cross section of the reaction and a MC simulation is estimated to be about 1.5 per day, which can provide a confidence level of the signal greater than 5(sigma ) with a beam time longer than 16 days. According to a MC simulation that evaluates the energy losses of particles in materials and the performance of three spectrometers, the estimated resolution and the predicted shape of the missing mass spectrum are presented. This work provides a new experimental concept for the search for multineutron states in future experiments with an electron beam.

We present a relativistic mean-field model that incorporates charge symmetry breaking (CSB) of nuclear force via the ( omega )-( rho ^0 ) meson mixing, along with corrections to the electromagnetic interaction including the nucleon form factors, first-order vacuum polarization, and Coulomb exchange and pairing terms. The model parameters are refitted using the mass differences of ( T = 1/2 ) mirror nuclei and ground-state properties of magic nuclei, yielding DD-ME-CSB parameter set. The DD-ME-CSB parameter set reproduces the mass differences of mirror nuclei reasonably well up to ( T = 2 ), demonstrating the importance of ( omega )-( rho ^0 ) mixing. A connection of the present model to a Skyrme-type CSB interaction is also established through a gradient expansion of the energy density functional.