The European Physical Journal A最新文献

We report on the measurement and analysis of elastic scattering angular distributions for the (^{13})C+(^{119})Sn system at two bombarding energies: 40.0 and 46.9 MeV. In addition, inelastic scattering and single-neutron transfer reactions were measured at 46.9 MeV. The data were obtained using the same experimental setup previously employed in the (^{12})C+(^{119})Sn study, allowing for a direct comparison. Optical model analyses were performed using the São Paulo potential for the real part of the interaction, while the imaginary part was treated both phenomenologically and via normalization of the real potential. Coupled-reaction-channels calculations were carried out, including couplings to inelastic excitations and one-neutron transfer channels. This approach yielded an improved description of the elastic scattering data across the full angular range for both energies. A direct comparison with the (^{12})C+(^{119})Sn results indicates that the additional neutron in (^{13}textrm{C}) enhances absorption from the elastic channel. These findings highlight the sensitivity of near-barrier reaction dynamics to moderately bound valence nucleons and underscore the importance of coupling effects in accurately describing heavy-ion interactions.

We investigate whether the first discovered fluorine-rich CEMP-no star, CS 29498−043, can be explained by a very metal-poor rotating massive star. We consider single rotating stellar models of 20 (M_{odot }) at a metallicity of (Z = 10^{-5}), exploring initial rotation rates from (upsilon _textrm{ini}/upsilon _textrm{crit} = 0) to 0.7 in increments of 0.1 ((0<upsilon _textrm{ini}<644) km s(^{-1})). Rotational mixing enhances the production of light elements in the H–He layers, including fluorine. The ejected material can be nitrogen-rich without being fluorine-rich, whereas fluorine-rich ejecta are always predicted to be nitrogen-rich. The model providing the best fit to the abundances of CS 29498−043 is the (upsilon _textrm{ini}/upsilon _textrm{crit} = 0.6) model ((upsilon _textrm{ini} = 547) km s(^{-1})), which reproduces C, N, O, Na, Mg, and Al within the observational uncertainties. However, the predicted [F/Fe] (=2.8) exceeds the observed value of [F/Fe] (=2.0 pm 0.4). By simultaneously varying the (^{15})N((alpha ,gamma ))(^{19})F and (^{19})F((alpha ,p))(^{22})Ne reaction rates within their acceptable ranges, the [F/Fe] ratio in the (upsilon _textrm{ini}/upsilon _textrm{crit} = 0.6) model can be reduced to 2.2, providing a plausible solution to the abundance pattern of CS 29498−043. Our results support the hypothesis that fluorine-rich CEMP-no stars may originate from material enriched by a single, metal-poor, rotating massive star. A potential observational test of this scenario may be to check whether the nitrogen and fluorine abundances observed at the surface of CEMP-no stars are correlated.

Hartree–Fock equations for finite-range interactions in a slab of nuclear matter are presented and solved using an algorithm based on the Lagrange mesh method. This approach is faster and more efficient than the Numerov algorithm commonly used in the literature. Thanks to the improved numerical accuracy, we were able to perform calculations with sufficiently large boxes to minimize the impact of Friedel oscillations on the final results, achieving a precision on the surface energy within a few dozens of keV. Results are presented for several Gogny interactions that have not been previously discussed. In addition, the inclusion of the spin–orbit term is examined, showing a net reduction of 1.2–1.9 MeV in the surface energy.

We show for the first time that the low-spin ((J le 4^+)) six-(alpha ) condensate candidate states in (^{24})Mg, recently reported by Fujikawa et al. (Phys Lett B 848:138384, 2024), are well described by the superfluid (alpha )-cluster model (SCM). This is achieved by a rigorous treatment of the Nambu-Goldstone (NG) zero mode as the order parameter of condensation in the finite six-(alpha ) system. We find that a roton rotational band with a large moment of inertia is built on the first excited NG (0^+) state, analogous to the roton bands observed in three-, four-, and five-(alpha ) condensates in (^{12})C, (^{16})O, and (^{20})Ne, respectively. Remarkably, our calculated roton band reproduces the well-known molecular resonance with a (^{12})C((0_2^+))+(^{12})C((0_2^+)) structure ((16^+)) observed at (E_mathrm{c.m.} = 32.5) MeV in inelastic (^{12})C+(^{12})C scattering. This result provides a unified description of both the low-spin six-(alpha ) condensate states and the high-spin (^{12})C((0_2^+))+(^{12})C((0_2^+)) molecular resonance. Analysis of the wave functions reveals a large overlap between the SCM states and a geometrical (^{12})C((0_2^+))+(^{12})C((0_2^+)) configuration. This dual nature—the coexistence of superfluidity and crystallinity—identifies these states as a signature of a supersolid.

In this work, we construct the DK, (D^*K), (DK^*), BK, (B^*K) and (BK^*) type (color-singlet-color-singlet) currents to study the masses and pole residues of charm-strange hadronic states and their bottom analogs with (J^P) = (0^+) and (1^+) by using two-point QCD sum rules, where the vacuum condensates are considered up to dimension 12. The predicted masses with DK, (D^*K) and (DK^*) type currents are (2.322_{ - 0.072}^{ + 0.066}) GeV, (2.457_{ - 0.068}^{ + 0.064}) GeV and (2.538_{ - 0.062}^{ + 0.059}) GeV. These results are consistent well with the experimental data of (D^*_{s0}(2317)), (D_{s1}(2460)) and ({D}_{s1}(2536)), respectively. The mass predicted with (BK^*) type current is (6.158_{ - 0.063}^{ + 0.061}) GeV, which is consistent with the (B_{sJ}(6158)) structure observed by LHCb collaboration. Finally, the theoretical results for BK and (B^*K) type currents are (5.970_{ - 0.064}^{ + 0.061}) GeV and (6.050_{ - 0.064}^{ + 0.062}) GeV, which are higher than the thresholds of BK and (B^*K) molecules.

The breaking of axial symmetry in nuclei enables otherwise precluded behaviours, making it an interesting phenomenon to study. Experimental fingerprints such as very low-lying (2_2^+) states suggest pronounced triaxial deformation for the neutron-rich ruthenium isotopes. Nevertheless, theoretical calculations differ in the description of the triaxial deformation and its evolution with neutron number, making experimental data crucial to understanding it. We investigated the evolution of the degree of triaxiality and (gamma ) rigidity in neutron-rich ruthenium isotopes by measuring lifetimes of excited states in (^{108-112})Ru with the recoil distance Doppler-shift method. The experiment was carried out at the Grand Accélérateur National d’Ions Lourds using the Advanced Gamma Tracking Array coupled to the Variable Mode Spectrometer. We obtained B(E2) values for 29 transitions in the studied nuclei and compared them with fully microscopic symmetry conserving configuration mixing calculations, and phenomenological generalized triaxial rotor and triaxial particle-rotor models. The models generally reproduce the measured transition strengths, and show an increase in triaxiality with neutron number, reaching near maximum triaxiality in (^{112})Ru. The results are consistent with a transition from (gamma ) soft to (gamma ) rigid motion as the neutron number increases.

Neutron-induced reactions play an important role in fundamental nuclear physics, nuclear astrophysics, and applications. In the case of reactions on rare isotopes, there are limited options for direct experimental measurements. The Neutron Target Demonstrator project at Los Alamos National Laboratory seeks to test the feasibility of moderating spallation neutrons within a 1 m(^3) graphite cube to create a standing neutron target for neutron-induced reaction measurements in inverse kinematics. This paper presents the results of experimental neutron flux distribution tests using neutron sources (ranging from 1 keV to 50 MeV) created by accelerators at the University of Notre Dame and Texas A&M University. Measurements were made with both the full graphite cube as well as a ”half cube” setup in which half of the graphite cube was removed. The measured distributions agree with simulated distributions in the case of the full cube moderator, although there remain discrepancies in certain cases for the half cube moderator. The results shown here will provide useful information for an upcoming experimental campaign to test the neutron target proof-of-principle.

Astrophysical reaction rates for reactions with proton-rich isotopes of Ne to Bi from stability to the proton dripline were calculated with an updated version of the SMARAGD statistical model (Hauser-Feshbach) code. Here, the focus was on reactions with protons or (alpha ) particles as required for nucleosynthesis in proton-rich matter. For completeness, also neutron-induced reactions are provided for the same set of targets. Some comments on dependencies of rates on various nuclear properties and on the appropriate way to compare to experiments are given. The new rate set for charged-particle induced reactions provides a better description of experimental data than previously widely used rates, especially for reactions involving (alpha ) particles.

Tensor polarization in spin-1 systems is essential for accessing unique observables in nuclear and hadronic structure studies, particularly in experiments probing gluon and quark distributions. Accurate measurement of tensor polarization enhances sensitivity to tensor-polarized observables, which are critical for isolating partonic degrees of freedom in nuclei and exploring nucleon structure in bound states. This work presents an overview of limitations in direct measurements of tensor polarization from the NMR absorption line and a proposal for improved measurement instrumentation and techniques. These methods attempt to avoid biased assumptions to improve precision while helping to quantify measurement error, especially under the application of frequency-selective radiofrequency techniques that locally manipulate spin populations. Non-equilibrium spin dynamics, spin diffusion, and rate equation modeling are helpful to characterize the response of the spin system in these circumstances. The impact of instrumental constraints, including fitting error, binning resolution, sweep rate, data acquisition system bandwidth, and evolution of the spin system during NMR measurements, is discussed. Mitigation strategies are proposed using real-time signal processing and edge computing. These developments can support accurate, adaptive control of tensor polarization and improve the figure of merit in scattering experiments that rely on spin-1 polarized targets.