The European Physical Journal A最新文献

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.

The sudden rise of nuclear collectivity above the pairing gap is revealed in this work as the primary source for the relative increase of the symmetry energy with respect to the ground state, as originally suggested by Donati and collaborators. This finding is uncovered by available data on giant dipole resonances built on excited states and 1(hbar omega ) shell-model calculations of the myriads of products of electric dipole matrix elements that compose the nuclear dipole polarizability of the ground and first-excited states. At the temperatures involved in stellar environments, a larger symmetry energy impacts stellar collapse, the nucleosynthesis of heavy elements and the nuclear equation of state of hot neutron stars.

The nature of low-lying scalar and axial-vector charmed mesons has been debated for decades, with hadronic molecular and compact tetraquark models being prominent candidates. These two models predict quite different features for the accessible SU(3) multiplets in the scalar and axial-vector sectors, which can be tested through lattice calculations at SU(3) symmetric points. In this work, we perform lattice calculations for both scalar and axial-vector charmed mesons with an SU(3) symmetric pion mass about 613 MeV for the SU(3) [6] and ([overline{15}]) multiplets. We find that the [6] multiplet exhibits attractive interactions in both scalar and axial-vector sectors, while the ([overline{15}]) multiplet shows repulsive interactions in both sectors. The energy shifts in the scalar and axial-vector sectors are compatible with each other within uncertainties. These results are fully consistent with the hadronic molecular picture, while challenging the compact tetraquark model, which predicts the existence of low-lying ([overline{15}]) states in the axial-vector sector but not in the scalar sector.

We extend our recent study of the Universal Mass Equation for equal-quantum excited-states sets reported by Roper and Strakovsky (Eur Phys J A 61:102, 2025). The masses of twelve baryon sets and sixteen meson sets, with only two equal-quantum excited states in each set, using Breit-Wigner PDG2024 masses and their uncertainties at fixed (J^P) for baryons and (J^{PC}) for mesons, are fitted by a simple one-parameter logarithmic function, (M_n = alpha ~Ln(n) + M_1), where n is the level of radial excitation. Two accurate masses that start a set are used to calculate four higher masses in the set accurately. It is noted that (alpha ) values for (bbar{b}) equal-quantum excited-states sets accurately lie on a straight line, whose line parameters can be used to calculate (alpha ) and predict higher mass states for (bbar{b}) sets that have only one known member.

The precise determination of the free neutron lifetime is of great significance in modern precision physics. This key observable is linked to the mixing of up and down quarks via the Cabibbo-Kobayashi-Maskawa matrix element (V_{ud}), and the abundance of primordial elements after the Big-Bang Nucleosynthesis. However, the two leading measurement techniques for the neutron lifetime currently yield incompatible results, a discrepancy referred to as the neutron lifetime puzzle. To address the systematic uncertainties arising from neutron interactions with material walls, the (tau )SPECT experiment employs a fully magnetic trap for ultra-cold neutrons (UCNs). UCNs velocities are extremely low-energy neutrons with typical velocities below (8,text {m/s}), which can be manipulated using magnetic fields, gravity, and suitable material guides, whose surface can reflect them at any angle of incidence. To precisely study and characterize UCN behavior during production, guidance, storage, and detection in (tau )SPECT, we have developed a dedicated simulation framework. This framework is built upon the externally developed UCN Monte Carlo software package PENTrack and is enhanced with two companion tools: one for flexible and parametrizable upstream configuration of PENTrack such that the simulation’s input settings can be adjusted to reproduce the experimental observations. The second package is used for analyzing, visualizing, and animating simulation data. The simulation results align well with experimental data obtained with (tau )SPECT at the Paul Scherrer Institute and serve as a powerful resource for identifying systematic uncertainties and guiding future improvements to the current experimental setup.

Differential cross sections of the elastic and inelastic scattering of 14.1 MeV neutrons on (^{12})C for (^{12})C(n,n(_{0,1-4,7}))(^{12})C channels were measured in the framework of the TANGRA project. The experiment was carried out using the tagged neutron method which helped to reduce the background of random coincidences, determine the neutron flux on the target, and determine the energy of scattered neutrons by the time-of-fligh. The total reaction cross sections were calculated by approximating the measured differential cross sections by expansions in Legendre polynomials and then integrating over the entire range of solid angles. The measured values of the differential cross sections are generally in agreement with the experimental data of other authors within the measurement uncertainties. The obtained data for the total partial cross sections for elastic scattering are in agreement within uncertainties with the evaluated data from various nuclear data libraries (ENDF/B-VIII.0, EAF-2010, FENDL-3.1, JEFF-3.3, JENDL-4.0/HE). The cross section for (^{12})C(n,n(_1))(^{12})C channel is in agreement with the data from FENDL-3.1 and JENDL-4.0/HE. The total experimental cross section for the (^{12})C(n,n(_{2-7}))(^{12})C channels, which lead to the decay of the (^{12})C nucleus into 3(alpha )-particles obtained in the present work in combination with the experimental data of other authors are consistent with similar cross sections evaluated from the ENDF/B-VIII.0 and JEFF-3.3 libraries, but is significantly smaller than the one estimated from the EAF-2010 library. This result may indicate the need to reduce the evaluations of helium production in carbon compounds under the operating conditions of a fusion reactor, previously made based on the EAF library.

The MORA experimental setup is designed to measure the triple-correlation (D) parameter in the nuclear beta decay of trapped and polarized (^{23})Mg(^+) and (^{39})Ca(^+) ions. The (D) coefficient is sensitive to potential violations of time-reversal invariance – and, via the CPT theorem, to CP violation. The experimental configuration consists of a transparent Paul trap surrounded by a detection setup with alternating (beta ) and recoil-ion detectors. The octagonal symmetry of the detection setup optimizes the sensitivity of positron-recoil-ion coincidence rates to the (D) correlation, while reducing systematic effects. MORA utilizes an innovative in-trap laser polarization technique. The design and performance of the ion trap and associated optics, lasers and (beta ) and detection system are presented. The recent experimental demonstration of the polarization technique is described.