The European Physical Journal A最新文献

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.

The HFB3 program solves the axial nuclear Hartree–Fock–Bogoliubov (HFB) equations using bases formed by either one or two sets of deformed Harmonic Oscillator (HO) solutions with D1-type and D2-type Gogny effective nucleon–nucleon interactions. Using two sets of HO solutions shifted along the z-axis (2-center basis) allows to accurately describe highly elongated nuclear systems while keeping a moderate basis size, making this type of basis very convenient for the description of the nuclear fission process. For the description of odd–even and odd–odd systems, the equal-filling-approximation is used. Several observables can be calculated by the program, including the mean values of the multipole moments, nuclear radii, inertia tensors following Adiabatic Time-Dependent Hartree–Fock–Bogoliubov (ATDHFB) or Generator Coordinate Method (GCM) prescriptions, local and non-local one-body densities, local and non-local pairing densities, some fission fragment properties, etc. The program can ensure that the mean values associated with some specific operators take pre-defined values (constraints). Such constraints can be set on the usual multipole moments (for protons, neutrons or total mass). This program can be used as a monoprocess and monothreaded CLI executable, or through full-featured Python bindings (available through the Python Package Index PyPI).

There is growing evidence that high-energy scattering processes involving nuclei can offer unique insights into the many-body correlations present in nuclear ground states, in particular those of deformed nuclei. These processes involve, for instance, the collective anisotropic flows in heavy-ion collisions, or the diffractive production of vector mesons in photo-nuclear ((gamma A)) interactions. In this paper, we use a classical approximation and simple analytical models in order to exhibit characteristic and universal features of ground-state correlation functions that result from the presence of a deformed intrinsic state. In the case of a small axial quadrupole deformation, we show that the random rotation of the intrinsic density of the nucleus leads to a specific quadrupole modulation of the lab-frame two-body density as a function of the relative azimuthal angle. As a phenomenological, albeit academic application, we analyze the diffractive production of vector mesons in high-energy (gamma +^8)Be collisions. This demonstrates with the simplest deformed nucleus how the two-body correlations impact the |t| dependence of the incoherent cross sections.

Cross-section measurements of ((alpha ,gamma )) reactions on (^{106})Cd, (^{102})Pd, and (^{104})Pd have been performed at center-of-mass energies between (approx ) 7.9 and 11 MeV, which lie within the Gamow energy window relevant to the p-process. The determined total cross sections range between 1.4 and 257 (mu )b. Astrophysical S factors were also derived from the experimental cross sections. Statistical model calculations were performed using version 2.0 of the TALYS code and compared with the new data. An overall very good agreement between theory and experiment was found. In addition, the effect of different combinations of nuclear input parameters entering the stellar reaction-rate calculations was investigated.