The European Physical Journal A最新文献

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.

We explore the impact of perturbative pions on the Unitarity Expansion in the two-nucleon S-waves of Chiral Effective Field Theory at next-to-next-to leading order ((textrm{N}^{2})LO). Pion exchange explicitly breaks the nontrivial fixed point’s universality, i.e.  invariance of S waves under both conformal and Wigner’s combined (textrm{SU}(4)) spin–isospin transformations. On the other hand, Unitarity explicitly breaks chiral symmetry. The two seem incompatible in their respective exact-symmetry limits. ({upchi }textrm{EFT}) with Perturbative Pions in the Unitarity Expansion resolves the apparent conflict in the Unitarity Window (phase shifts (45^circ lesssim delta (k)lesssim 135^circ )), i.e.  around momenta (kapprox m_pi ) most relevant for low-energy nuclear systems. Its only LO scale is the scattering momentum; NLO adds only scattering length, effective range and non-iterated one-pion exchange (OPE); and (textrm{N}^{2})LO only once-iterated OPE. Agreement in the ({phantom {0}}^{1}textrm{S}_{0}) channel is very good. Apparently large discrepancies in the ({phantom {0}}^{3}textrm{S}_{1}) channel even at (kapprox 100;textrm{MeV}) are remedied by taking at (textrm{N}^{2})LO only the central part of OPE. In contradistinction to the tensor part, it is identical in the ({phantom {0}}^{1}textrm{S}_{0}) and ({phantom {0}}^{3}textrm{S}_{1}) channels. Both channels then match empirical phase shifts and pole parameters well within mutually consistent quantitative theory uncertainty estimates. Pionic effects are small, even for (kgtrsim m_pi ). Empirical breakdown scales are consistent with (overline{Lambda }_{textrm{NN}}=frac{16pi f_pi ^2}{g_A^2M}approx 300;textrm{MeV}), where iterated OPE is not suppressed. We therefore conjecture: Both conformal and Wigner symmetry in the Unitarity Expansion show persistence, i.e.  the footprint of both combined dominates even for (kgtrsim m_pi ) and is more relevant than chiral symmetry, so that the tensor/Wigner-(textrm{SU}(4)) symmetry-breaking part of OPE does not enter before (textrm{N}^{3})LO. We also discuss the potential relevance of entanglement and possible resolution of a conflict with the strength of the tensor interaction in the large-(N_C) expansion.

We report, for the first time, the emergence of a secondary bow with ripples in (^{12})C+(^{12})C nuclear rainbow scattering. This finding was achieved by studying the experimental angular distributions in (^{12})C+(^{12})C scattering at incident energies (E_L) = 240 and 300 MeV, utilizing an extended double-folding model. This model accurately describes all diagonal and off-diagonal coupling potentials derived from the microscopic wave functions for (^{12})C. Although the observed angular distributions of rainbow scattering at large angles (approaching (90^circ )) are complicated by the symmetrization of two identical bosonic nuclei, the Airy minimum, associated with a dynamically generated secondary bow with ripples, is clearly identified at approximately 77(^circ ) for 240 MeV in the fall-off region of the primary nuclear rainbow. This finding, along with previous findings in the (^{16})O+(^{12})C and (^{13})C+(^{12})C systems, reinforces the concept of a secondary bow in nuclear rainbow scattering.

The series of investigations focused on post-neutron fragment distributions, i.e. fractional and total independent yields (Y(Z,A_p), Y(A_p)), isotonic yields of post neutron fragments (Y(N_p)), kinetic energy distributions of secondary fragments (KE_p), and the various influences on them as well as of different correlations between pre- and post-neutron fragment quantities (performed for ²³⁵U(n_th,f), ²³⁹Pu(n_th,f) and ²⁵²Cf(SF)) is ending now with a deeper investigation devoted to ²³³U(n_th,f). This has involved comprehensive prompt emission calculations (performed with the DSE model code) by using reliable pre-neutron fragment distributions Y(A,TKE) (5 sets of experimental data and a calculated one) and two fragmentation ranges (deterministically constructed by using reliable sets of the charge polarization ΔZ(A) and rms(A) of the isobaric charge distribution). As TXE partitions, beside that based on modeling at scission, another one based this time on the so-called “experimental temperature ratio R_T” provided by a new method (without resorting to prompt emission model calculations for the fit of ν(A) data as other codes do) was employed. This study not only confirmed and strengthened the previously observed features of how the structures of Y(A_p) and Y(N_p) are influenced by model ingredients and Y(A,TKE) but also has revealed that the most significant influence on prompt emission and all post-neutron fragment distributions is that of the TXE partition. The good description of existing experimental data of Y(Z,A_p), Y(A_p), KE_p(Z), KE_p(A_p) for ²³³U(n_th,f) by the DSE results obtained with the TXE partition based on modeling at scission and several Y(A,TKE) can be considered as an indirect validation of these Y(A,TKE) distributions of pre-neutron fragments. The sawtooth shape of the nice correlation between the excitation energy E* of fully accelerated pre-neutron fragments and KE_p of post neutron fragments (looking as a reflection in mirror of the sawtooth shape of ν(A)) is maintained regardless of the employed fragmentation range, TXE partition and Y(A,TKE). The almost perfect overlap of E*(KE_p) in the case of ^{235, 233}U(n_th,f) (which might seem intuitive because the even-even compound nuclei ^{236, 234}U undergoing fission are close neighbors with similar nuclear properties) is explained in detail by investigating the beahviours of all physical quantities and distributions which are involved in this correlation.