The European Physical Journal A最新文献

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.

In this paper, we explore the mass spectra of (qqbar{q}bar{q}), (ssbar{s}bar{s}) and (qqbar{s}bar{s}) tetraquarks by employing Regge phenomenology. We calculate the range for ground state masses of (qqbar{s}bar{s}) tetraquarks, and estimate the Regge parameters for their trajectories in ((J,M^2)) plane. Using these Regge parameters we have calculated range for the excited state masses of (qqbar{q}bar{q}), (ssbar{s}bar{s}) and (qqbar{s}bar{s}) tetraquarks in ((J,M^2)) plane. Also, we have investigated the mass spectra of (qqbar{q}bar{q}), (ssbar{s}bar{s}) and (qqbar{s}bar{s}) tetraquarks for their excited radial states in ((n,M^2)) plane. We predict the potential quantum numbers of some newly observed experimental states, which necessitate additional validation, and assess the higher orbital and radial excited states that may be identified in the near future. The obtained mass relations and mass values of tetraquarks can be useful in future experimental searches and the spin-parity assignment of these states. Our findings provide valuable insights into the structure and properties of tetraquarks, contributing to the broader understanding of Quantum Chromodynamics (QCD).

Based on the HYBRID model, the calculated production cross sections agree well with the experimental data in the reactions (^{58})Ni + (^{208})Pb and (^{64})Ni + (^{130})Te. In the (^{124,130,136})Te + (^{208})Pb reactions, it can be found that as the N/Z ratio of the projectile increases, the target is more likely to pick up neutrons, resulting in a shift of the cross sections of the target-like-fragment towards the neutron-rich side. The effect of the incident energy in (^{136})Te + (^{208})Pb reaction is studied, and it is found that the primary cross section of neutron-rich nuclei is sensitive to the incident energy, and the final cross section of neutron-deficient nuclei is sensitive to the incident energy.

The study of collectivity phenomena in atomic nuclei, such as nuclear deformation, provides essential information to characterize the nuclear potential in the different mass regions of the nuclear chart. The use of inelastic reactions in combination with particle-(gamma ) coincidences is a powerful experimental tool utilized to characterize near-ground excited states in reactions using deformed nuclei as targets and light-beam isotopes. This allows for the simultaneous study of both the states of nuclei in the beam and the target. The present work reports the first attempt to study the first excited states of the deformed (^{154})Sm isotope by measuring the Differential Cross-Section of the inelastic excitation of the target system (^{7}) Li beam (+) (^{154}) Sm. The particle (gamma )-ray coincidence technique has been used to study the (^7)Li + (^{154})Sm inelastic reactions at 26 MeV beam energy. Charged particles were detected using an array of (Delta E-E) phoswich detectors, while (gamma )-ray radiation was registered using two arrays of LYSO(Ce) detectors. The results were analyzed using coupled-channel calculations with the FRESCO code of the inelastic cross-section for different nuclear potentials. The Differential Cross-Section for inelastic excitations of (^{154})Sm of (2^+) ((E^{star }=0.082) MeV), (4^+) ((E^{star }=0.267) MeV), and (6^+) ((E^{star }=0.544) MeV), as well as the (1/2^-) ((E^{star }=0.478) MeV) state of the (^7)Li projectile is reported for the first time. Theoretical comparisons suggest that the (0^+rightarrow 4^+) and (0^+rightarrow 6^+) transitions of (^{154}) Sm are crucial to describe how these states are populated. In this work, the cross section of the inelastic scattering reaction (^7)Li(+^{154})Sm at 26 MeV beam energy was studied and compared with coupled channel calculations using modified potentials to understand the influence of different coupling mechanisms. The analysis of (^{154})Sm suggests that it should be considered a quantum rotor in which each excited state represents an addition of the angular momentum of (l=2hbar ). The experimental data also indicate that in addition to the ground state (0^+), the (2^+) ((E^{star }=0.082) MeV), (4^+) ((E^{star }=0.267) MeV), and (6^+) ((E^{star }=0.544) MeV) states of the target nucleus should be added to the coupling scheme, as well as the ground state (3/2^-) and the (1/2^-) ((E^{star }=0.478) MeV) of the projectile nucleus.

A new experimental area, the NEAR station, has recently been built at the CERN n_TOF facility, at a short distance from the spallation target (3 m). The new area, characterized by a neutron beam of very high flux, has been designed with the purpose of performing activation measurements of interest for astrophysics and various applications. The beam is transported from the spallation target to the NEAR station through a hole in the shielding wall of the target, inside which a collimator is inserted. The new area is complemented with a (gamma )-ray spectroscopy laboratory, the GEAR station, equipped with a high-efficiency HPGe detector, for the measurement of the activity resulting from irradiation of a sample in the NEAR station. The use of a moderator/filter assembly is envisaged, in order to produce a neutron beam with quasi-Maxwellian energy distribution, of different thermal energies, necessary for the determination of Maxwellian Averaged Cross Sections of astrophysical interest. A new fast-cycling activation technique is also being investigated for measurements of reactions leading to isotopes of very short half life.

We used a nonlocal potential to account explicitly for nonlocalities in the (N-alpha ) scattering process. By fitting elastic (N-alpha ) angular distributions, over the energy range (0.84 - 20.97) MeV, we determined individual sets of nonlocal potential parameters and two global sets of fixed parameters one for (n-alpha ) and the other for (p-alpha ) elastic scattering. Our nonlocal potential model reproduced the elastic angular distributions for (N-alpha ) and the total elastic cross section for (n-alpha ) well. In addition, we calculated the nonlocal potential phase shifts corresponding to neutron and proton scattering off alpha particles. Our determined phase shifts are in good agreement with the experimental values. In addition, our nonlocal parameters reproduced the position of the (P3/2^-) resonance for the (n-alpha ) and (p-alpha ) scattering processes well. Accounting explicitly for nonlocalities in the (N-alpha ) interactions can benefit studies that consider the (t(d,N)alpha ) fusion reactions. The (t(d,n)alpha ) reaction is important for its 17.6 MeV energy yield per fusion reaction, for its carbon-free energy production. The less prominent reaction that leads to bremsstrahlung (gamma ) radiation is important as it provides real-time diagnostics regarding the fusion reaction rate.

This study explores the evolution of magnetized quark-gluon plasma (QGP) within the framework of relativistic magnetohydrodynamics (MHD), with a focus on understanding its temporal and spatial dynamics under the influence of intense magnetic fields. We employ a second-order viscous corrections to investigate the QGP’s evolution, where the plasma is subjected to a magnetic field generated in the early stages of relativistic heavy-ion collisions. The system is assumed to exhibit boost invariance along the longitudinal beam axis (z-coordinate) while undergoing transverse expansion. The magnetic field is modeled as a function of the proper time (tau ) and spatial coordinates (x, y), oriented perpendicular to the direction of fluid expansion. The QGP is assumed to possess infinite electrical conductivity. We solve the coupled Maxwell and conservation equations to obtain a detailed description of the energy density, flow velocity, and magnetic field evolution in the transverse plane of the viscous magnetized plasma. Additionally, we compute the hadron spectrum emerging from the freeze-out surface and compare our results with experimental observations, providing insights into the interplay between magnetization and the hydrodynamic evolution of QGP.

The simple system for beam spot position monitoring is described. It is based on the radiation-resistive SiC detectors. The visualization of the beam spot on the target is done with a dedicated BeamMon application using the ROOT environment.