The European Physical Journal A最新文献

Reactions induced by alpha particles, which play an important role in nuclear astrophysics, were investigated at energies below the Coulomb barrier using our IFIN-HH facilities. These include the 3 MV Tandetron™ accelerator [1], a local laboratory and the ultra-low background laboratory (mu )Bq [2] located in a salt mine. Thick Zn metal targets were irradiated at laboratory energies in the range (hbox {E}_{alpha }) = 5.4–8.0 MeV in 0.20 or 0.25 MeV steps. By measuring the prompt gamma-ray yields and the decay of radioisotopes produced in each reaction, in the Nuclear Astrophysics Group (NAG) and the (mu )Bq laboratories [3], we determined the thick target yields, which were subsequently used to evaluate the reaction cross sections. We succeeded in determining the cross section for (alpha )+⁶⁴Zn for the proton evaporation and radiative alpha capture channels at the lowest energies ever measured, deep inside the Gamow window for stellar processes at temperatures of 2–3 GK.

Systematic comparisons across theoretical predictions for the properties of dense matter, nuclear physics data, and astrophysical observations (also called meta-analyses) are performed. Existing predictions for symmetric nuclear and neutron matter properties are considered, and they are shown in this paper as an illustration of the present knowledge. Asymmetric matter is constructed assuming the isospin asymmetry quadratic approximation. It is employed to predict the pressure at twice saturation energy-density based only on nuclear-physics constraints, and we find it compatible with the one from the gravitational-wave community. To make our meta-analysis transparent, updated in the future, and to publicly share our results, the Python toolkit nucleardatapy is described and released here. Hence, this paper accompanies nucleardatapy, which simplifies access to nuclear-physics data, including theoretical calculations, experimental measurements, and astrophysical observations. This Python toolkit is designed to easily provide data for: (i) predictions for uniform matter (from microscopic or phenomenological approaches); (ii) correlation among nuclear properties induced by experimental and theoretical constraints; (iii) measurements for finite nuclei (nuclear chart, charge radii, neutron skins or nuclear incompressibilities, etc.) and hypernuclei (single particle energies); and (iv) astrophysical observations. This toolkit provides data in a unified format for easy comparison and provides new meta-analysis tools. It will be continuously developed, and we expect contributions from the community in our endeavor.

This investigation analyzes the angular distributions (ADs) for the ⁷Li + ¹³⁸Ba elastic scattering system across laboratory energies of 21–32 MeV using multiple nuclear potential approaches. Several computational methods were applied to assess the relative impacts of ⁷Li breakup and neutron transfer processes, particularly examining how the ¹³⁸Ba(⁷Li,⁶Li)¹³⁹Ba stripping reaction affects the elastic scattering channel. Our calculations demonstrate that ⁷Li breakup dominates over neutron transfer contributions in this system. Volume integrals for the real and imaginary potentials near the Coulomb barrier yield evidence for the existence of a breakup threshold anomaly.

The low-lying structure of the well-deformed nucleus (^{158})Gd has been revisited to elucidate the nature of the low-lying states in (^{158})Gd. Earlier (p, t) studies identified numerous 0(^+) states below 4.3 MeV, prompting questions about whether these states correspond to collective vibrations or shape coexistence. New and previously reported ((n,n^prime gamma )) measurements are combined, including (gamma )-(gamma ) coincidences, excitation functions, and angular distributions, to extract lifetimes and transition probabilities for 44 excited states up to 2.7 MeV, including 32 previously unmeasured levels. Our results confirm or revise (gamma )-ray placements and provide detailed transition strengths, revealing both weakly collective and strongly enhanced B(E2) and B(E1) transition probabilities. In particular, a tentative 0(^+) state at 2437.8 keV exhibits a strong interband B(E2) transition, which may be a candidate for a possible two-phonon ((beta beta )) excitation. Systematic comparisons with neighboring Gd isotopes, Hartree–Fock–Bogoliubov, and interacting-boson model predictions suggest that the first excited 0(^+) state in (^{158})Gd is predicted to be a (beta )-vibration, although it is weakly collective.

We also present results for lifetimes and transition probabilities for a number of negative parity states, including (hbox {K}^{pi }=0^-,1^-,2^-) sequences, perhaps providing insight into octupole collectivity and the interplay between quadrupole and octupole vibrations in deformed nuclei. The systematic presence of low-lying negative-parity bands and their interband transition strengths suggest that (^{158})Gd’s potential energy surface may support both quadrupole and octupole vibrational modes, in agreement with microscopic calculations [1,2,3].

The intermittency behavior of emitted particles produced in heavy ion collisions has been studied using both default and string melting modes of A Multi-Phase Transport (AMPT) model-generated data. In this article, the Scaled Factorial Moment (SFM) technique has been adopted to study the intermittency. The goal of the study is to search for critical points of strongly interacting matter. It is the region of QCD phase diagram where the properties of strongly interacting matter exhibit non-analytic behavior. Finding the exact location is citical point is one of the prime objectives to study fluctuation via SFM analysis. There are enormous number of results that have been published by the STAR, NA61/SHINE, NA49 collaborations for different collision systems. At SIS100 energies of FAIR, it is expected that the QCD phase diagram exhibits a first-order phase transition between hadronic matter and partonic matter at high net-baryon densities and moderate temperatures. So, it is also important to study such observables at lower energy too. The intermittency analysis is performed in 2D ((p_{x}-p_{y})) space for AMPT-generated data for Au+Au collisions at (E_{lab}=) 10 AGeV beam energy. It is also checked the existence of intermittency in the generated data by manipulating the Lund String Fragmentation parameter, b.

We report on new lifetime measurements of the yrast states (6(^+_1)​ to 12(^+_1)​) of (^{162})Er, performed using the Recoil Distance Doppler-Shift (RDDS) method at the Cologne FN Tandem accelerator. From the extracted lifetimes, B(E2) values were determined to trace the evolution of nuclear collectivity at high spin. At low-to-moderate spins ((I le 8)), the trend of the B(E2) values is described qualitatively by the Confined Beta-Soft (CBS) model, confirming the nucleus’s position in the transitional region between X(5) symmetry and the SU(3) rigid rotor limit. At higher spins ((I ge 10)), a sharp drop in the B(E2) strengths indicates the beginning of backbending, marking a clear breakdown of the purely collective description.

We report on the identification of a new isomeric state in (^{183})Ta populated via the ground-state (beta )-decay of (^{183})Hf. The experiment was performed at the KISS setup at RIKEN, where neutron-rich hafnium isotopes were produced via multi-nucleon transfer (MNT) reactions, followed by laser ionization of hafnium atoms, mass separation, and detection using an electron-gamma coincidence system. Isomeric spectroscopy was carried out by gating on different electron-gamma time correlations. A 459.1 keV (gamma )-ray transition was identified in delayed spectra, and a half-life of (41^{+6}_{-4}~upmu s) was extracted through time-distribution fitting. The 459.1 keV state in (^{183})Ta is known from previous work and has been assigned a Nilsson orbital configuration of (5/2^+[402]), while a proposed new isomeric state above it is interpreted as a (1/2^+[411]) configuration that decays to (5/2^+[402]) via a low-energy, unobserved E2 transition. This is consistent with the systematic trends in neighbouring odd-A nuclei and transition rate calculations.

In recent years, interest in experimental studies of (beta )-decay electron spectra – often referred to as (beta ) spectra – has been growing. This is particularly true for (beta ) transitions where the electron spectra are sensitive to the effective value of the weak axial coupling, (g_{textrm{A}}). Such measurements serve as important benchmarks for nuclear physics calculations and can also be used to characterize background in astroparticle physics experiments. In this work, a dedicated experiment has been carried out to investigate the spectral shape of the third-forbidden (^{87})Rb (beta )-decays, with the goal of estimating the effective (g_{textrm{A}}) value for this transition and of deriving the (hbox {T}_{1/2}) value. This was done by comparing the experimental spectral shape with the estimates from various phenomenological models. The (^{87})Rb source was embedded directly within the detector material of a new (hbox {Rb}_2hbox {ZrCl}_6) crystal scintillator; the data taking was performed deep underground at Gran Sasso National Laboratory. The obtained experimental half-life value for the studied process is (hbox {T}_{1/2} = 5.08(13) times 10^{10}) yr; while a (g_{textrm{A}}) value in the range 0.4–0.6 is obtained when accounting for uncertainties and depending on the model adopted as discussed in detail in the text.

The concept of seniority plays a central role in nuclear structure physics by classifying many-body states according to the number of unpaired nucleons. While exact seniority conservation holds in single-j systems with (j le 7/2), deviations arise for higher-j orbitals where residual interactions can mix states of different seniority. Surprisingly, certain states in systems with (j ge 9/2) exhibit partial conservation of seniority, remaining solvable even when the symmetry is expected to break. This paper reviews the theoretical foundation of the seniority scheme, its connection to pairing interactions and coefficients of fractional parentage, and the conditions under which solvability persists. Particular emphasis is placed on the (j=9/2) case, where two (v=4) states with (I=4) and (I=6) remain unmixed under arbitrary interactions. We discuss analytical proofs of their existence, numerical studies, and supporting experimental evidence from semi-magic nuclei across five regions of the nuclear chart. Extensions to symbolic shell-model approaches are also presented, highlighting their utility in exploring wave functions and symmetries in many-body systems.

The (^{116,118,120,122,124})In nuclei have been populated as fission fragments in reactions induced by heavy ions. Level schemes have been built from (gamma )-rays detected using the Gammasphere array. Medium-spin states of (^{118,120})In(_{69,71}) nuclei have been identified for the first time, while the level schemes of (^{116,122,124})In(_{67,73,75}) were enriched. The observed states at lower excitations and at medium spin can be described by the coupling of the proton g(_{9/2}) hole to the neutron or neutron-hole in the h(_{11/2}) orbital. This coupling can now be followed in all odd-odd In isotopes from (^{104})In(_{55}) to (^{126})In(_{77}).