Nuclear level density is important for evaluating nuclear reaction processes, but its microscopic investigation is not frequently performed. The present work applies a recently developed shell-model-based method to estimate the level density of fission products ${}^{133–137}\mathrm{Xe}$ and ${}^{135–138}\mathrm{Ba}$. The monopole-based universal interaction, $V_{\text{MU}}$, and the M3Y type spin-orbit interaction are combined to construct the shell-model Hamiltonian. The model space is truncated based on the binding energy of each configuration, estimated from the monopole interaction. The calculated level densities of ${}^{133–137}\mathrm{Xe}$ and ${}^{135–138}\mathrm{Ba}$ are in good agreement with available experimental data. The effects of spin-orbit and tensor forces on the nuclear level density and the shell effects in the spin distribution are discussed.

Isotope dependences of charge radii, i.e., isotope shifts, calculated by the Skyrme Hartree-Fock, the relativistic mean-field, and the relativistic Hartree-Fock calculations are compared against the experimental data of magic and semimagic nuclei. It is found that the tensor interaction plays a role in reproducing the “kink” behavior, irregularity of isotope shifts at the neutron magic number, in the relativistic Hartree-Fock approach. With several Skyrme models, it is found that the kink behavior can be reproduced with the spin-orbit interaction having nonzero isovector channel. The single-particle orbitals near the Fermi energy are crucial to determine the kink size. The effects of the symmetry energy and the pairing interaction are also discussed in relation to the kink behavior.

The Beam Energy Scan Theory (BEST) collaboration's equation of state (EoS) incorporates a three-dimensional Ising model critical point into the quantum chromodynamics (QCD) equation of state from lattice simulations. However, it contains four free parameters related to the size and location of the critical region in the QCD phase diagram. Certain combinations of the free parameters lead to acausal or unstable realizations of the EoS that should not be considered. In this work, we use an active learning framework to rule out pathological EoS efficiently. We find that checking stability and causality for a small portion of the parameters' range is sufficient to construct algorithms that perform with $>96$% accuracy across the entire parameter space. Though in this work we focus on a specific case, our approach can be generalized to any EoS containing a parameter space-class correspondence.

We present an alternative analysis of the ${}^{113}\mathrm{Cd}\beta$-decay electron energy spectrum in terms of spectral moments ${\mu }_n$, corresponding to the averaged values of $n\mathrm{th}$ powers of the $\beta$ particle energy. The zeroth moment ${\mu }_0$ is related to the decay rate, while higher moments ${\mu }_n$ are related to the spectrum shape. The here advocated spectral-moment method (SMM) allows for a complementary understanding of previous results, obtained using the so-called spectrum-shape method (SSM) and its revised version, in terms of two free parameters: $r=g_{\mathrm{A}}/g_{\mathrm{V}}$ (the ratio of axial-vector to vector couplings) and $s$ (the small vectorlike relativistic nuclear matrix element, $s$-NME). We present numerical results for three different nuclear models with the conserved vector current hypothesis (CVC) assumption of $g_{\mathrm{V}}=1$. We show that most of the spectral information can be captured by the first few moments, which are simple quadratic forms (conic sections) in the $(r,s)$ plane: An ellipse for $n=0$ and hyperbolas for $n\ge 1$, all being nearly degenerate as a result of cancellations among nuclear matrix elements. The intersections of these curves, as obtained by equating theoretical and experimental values of ${\mu }_n$, identify the favored values of $(r,s)$ at a glance, without performing detailed fits. In particular, we find that values around $r\approx 1$ and $s\approx 1.6$ are consistently favored in each nuclear model, confirming the evidence for $g_{\mathrm{A}}$ quenching in ${}^{113}\mathrm{Cd}$, and shedding light on the role of the $s$-NME. We briefly discuss future applications of the SMM to other forbidden $\beta$-decay spectra sensitive to $g_{\mathrm{A}}$.

We present cumulative fission product yields from the ${}^{238}\mathrm{U}(n,f)$ reaction at an incident energy of 4.6 MeV for fission products with half-lives from less than one second to several hours. We employed direct $\gamma$-ray spectroscopy to measure unseparated fission products with a conventional neutron activation analysis and a cyclic activation technique using the RApid Belt-driven Irradiated Target Transfer System (RABITTS). Yields were determined for 78 isotopes and isomers, covering the mass range $84\le A\le 148$ and the charge range from $33\text{(As)}\le Z\le 58\text{(Ce)}$. Our experimental cumulative yields are compared to the literature and evaluated data at $E_n\approx 0.5$ MeV from ENDF/B-VIII.0 and JEFF-3.3 libraries and with theoretical models using the gef and freya codes at $E_n=4.6$ MeV.

Stellar nuclear fusion reactions take place in a hot, dense plasma within stars. To account for the effect of these environments, the theory of open quantum systems is used to conduct pioneering studies of thermal and atomic effects on fusion probability at a broad range of temperatures and densities. Since low-lying excited states are more likely to be populated at stellar temperatures and increase nuclear plasma interaction rates, a ${}^{188}\mathrm{Os}$ nucleus was used as a target that interacts with an inert ${}^{16}\mathrm{O}$ projectile. Key results showed thermal effects yield an average increase in fusion probability of 15.5% and 36.9% for our test nuclei at temperatures of 0.1 and 0.5 MeV, respectively, compared to calculations at zero temperature. Thermal effects could be tested in a laboratory using targets prepared in excited states as envisaged in facilities exploiting laser-nucleus interactions.

We attempt to put forth the competing reaction mechanisms through residual cross section measurement in ${}^6\mathrm{Li}$ fusion with ${}^{93}\mathrm{Nb}$. The measured residual cross sections in the 24–43 MeV energy range are analyzed with the theoretical estimations from pace4, empire3.2.2, and alice23 statistical model codes. The replication of major $xn$-channel cross sections by empire with enhanced generalized superfluid model (EGSM) level density confirms that the population of $xn$-channel residues is through the complete fusion (CF) mechanism. The preequilibrium (PEQ) emission signatures were witnessed in the case of ${}^{97}\mathrm{Ru}$ residue populated via the $2n$ channel. Amplification of major experimental $p$- and $\alpha$-channel cross sections relative to the optimal theory was interpreted by considering the possibility of an incomplete fusion (ICF) process in addition to CF, owing to the low breakup threshold of the ${}^6\mathrm{Li}$ projectile. Thus, the ICF strength fraction $\left(F_{\mathrm{ICF}}\right)$ was estimated. The $F_{\mathrm{ICF}}$ turned out to be $\approx 8–20\%$ with an increasing trend and is found to be thoroughly higher than the deduced $F_{\mathrm{ICF}}$ for ${}^7\mathrm{Li}$ reaction on ${}^{93}\mathrm{Nb}$ target. In the case of weakly bound ${}^{6,7}\mathrm{Li}$-induced reactions, the first attempt is made to understand the influence of entrance channel parameters such as bombarding energy, $\alpha$-separation energy, Coulomb factor, mass asymmetry, neutron skin thickness, angular momentum, etc., on $F_{\mathrm{ICF}}$. The observed trend of the isomeric cross section ratios from the relative population of isomeric and ground states of ${}^{96,94}\mathrm{Tc}$ radionuclides is also discussed.

The impacts of various symmetry energy parameters on the properties of neutron stars (NSs) have been recently investigated, and the outcomes are at variance, as summarized in Table III of Phys. Rev. D 106, 063005 (2022). We have systematically analyzed the correlations of slope and curvature parameters of symmetry energy at the saturation density (${\rho }_0=0.16{\text{fm}}^{-3}$) with the tidal deformability and stellar radius of nonspinning neutron stars in the mass range of $1.2–1.6M_{\odot }$ using a large set of minimally constrained equations of state (EoSs). The EoSs at low densities correspond to the nucleonic matter and are constrained by empirical ranges of a few low-order nuclear matter parameters from the finite nuclei data and the pure neutron matter EoS from chiral effective field theory. The EoSs at high densities ($\rho >1.5–2{\rho }_0$) are obtained by a parametric form for the speed of sound that satisfies the causality condition. Several factors affecting the correlations between the NS properties and the individual symmetry energy parameters usually considered in the literature are explored. These correlations are quite sensitive to the choice of the distributions of symmetry energy parameters and their interdependence. But, variations of NS properties with the pressure of $\beta$-equilibrated matter at twice the saturation density remain quite robust which may be due to the fact that the pressure depends on the combination of multiple nuclear matter parameters that describe the symmetric nuclear matter as well as the density dependence of the symmetry energy. Our results are practically insensitive to the behavior of EoS at high densities.

Emulators for low-energy nuclear physics can provide fast and accurate predictions of bound-state and scattering observables for applications that require repeated calculations with different parameters, such as Bayesian uncertainty quantification. In this paper, we extend a scattering emulator based on the Kohn variational principle (KVP) to momentum space (including coupled channels) with arbitrary boundary conditions, which enable the mitigation of spurious singularities known as Kohn anomalies. We test it on a modern chiral nucleon-nucleon $\left(NN\right)$ interaction, including emulation of the coupled channels. We provide comparisons between a Lippmann-Schwinger equation emulator and our KVP momentum-space emulator for a representative set of neutron-proton $\left(np\right)$ scattering observables, and also introduce a quasi-spline-based approach for the KVP-based emulator. Our findings show that while there are some trade-offs between accuracy and speed, all three emulators perform well. Self-contained Jupyter notebooks that generate the results and figures in this paper are publicly available.

High-energy vector meson photoproduction is an important tool for studying the partonic structure of matter at low Bjorken $x$. In the Good-Walker (GW) paradigm, the cross section $d\sigma /dt$ for coherent production of vector mesons or other final states depends the average transverse distribution of gluons, while the incoherent cross section depends on fluctuations in the nuclear structure, due to variations in nucleon positions, and/or gluonic hot spots. However, predictions of the the GW paradigm seemingly conflict with data from multiple experiments which observe coherent production of vector mesons accompanied by nuclear excitation, or in peripheral relativistic heavy-ion collisions. These data are consistent with a simpler, semiclassical approach. I will discuss this contradiction and explore how and why GW fails. I will also contrast the significant differences in incoherent photoproduction on ${}^{197}\mathrm{Au}$ and ${}^{208}\mathrm{Pb}$ targets in the GW approach with the much smaller expected differences in their low-$x$ gluon content.

In this work, the canonical thermodynamical model for nuclear multifragmentation has been updated with a realistic nuclear equation of state. Mass distribution, intermediate mass fragment multiplicity, and isospin sensitive observables have been investigated with a semi-microscopic approach of determining nuclear binding and excitation energies. Production of neutron-rich isotopes as well as isoscaling and isobaric yield ratio parameters have been significantly modified due to inclusion of this realistic nuclear equation of state.

Isotopic yield distributions of nuclei produced in peripheral collisions of ${}^{80}\mathrm{Kr}+{}^{40,48}\mathrm{Ca}$ at 35 MeV/nucleon are studied. Experimental results obtained by the FAZIA Collaboration at the LNS facility in Catania are compared with calculations performed with the statistical multifragmentation model (SMM). The fragments with atomic number $Z=19–24$ observed at forward angles are successfully described with the ensemble method previously established for reactions at higher energy. Using the SMM results, the isotopic compositions of the projectile residues are reconstructed. The results indicate a significant isospin exchange between the projectile and target nuclei, not far from isospin equilibrium, during the initial phase of the reaction. The two groups of light fragments with $Z=1–4$, experimentally distinguished by their velocities relative to coincident heavy projectile fragments, are found to originate from different sources. The isotopic composition of the slower group is consistent with emission from a low-density neck, enriched in neutrons, and satisfactorily reproduced with SMM calculations for a corresponding neck source of small mass.

The cross section of the ${}^{65}\mathrm{Cu}\left(n,p\right){}^{65}\mathrm{Ni}$ reaction was studied experimentally at three different neutron energies using an activation technique. The quasimonoenergetic neutrons were produced via the ${}^7\mathrm{Li}\left(p,n\right)$ reaction at the 14UD BARC-TIFR Pelletron facility in Mumbai, India. Al monitor foils along with Cu samples were activated to determine the incident neutron flux. The activities of the reaction products were measured using a high resolution high purity germanium spectrometry system. Statistical model calculations were performed using the reaction codes talys (ver. 1.9) and empire (ver. 3.2.3) from the reaction threshold to the neutron energy of 25 MeV. Additionally, the effects of various combinations of the theoretical nuclear level densities (NLDs), optical model potentials (OMPs), preequilibrium models (PEs), and γ-ray strength functions (γ SFs) were considered for the reproduction of experimental data. The input parameters needed in theoretical calculations to reproduce the present and previous measurements were taken from the RIPL-3 database. The present results are compared with the previous measurements, with the latest evaluations of the ENDF/B-VIII.0, JEFF-3.3, JENDL-4.0/HE, CENDL-3.2, TENDL-2019, and FENDL-3.2 libraries, and with the theoretically calculated values based on talys and empire codes. Furthermore, the cross section of the ${}^{65}\mathrm{Cu}\left(n,p\right){}^{65}\mathrm{Ni}$ reaction was estimated within the neutron energies of 14–15 MeV using different systematic formulas. These estimated cross sections by various systematic formulas were compared with the available experimental data. The present data will help to understand the nuclear reaction theory (models) in higher energy regions and improve the evaluated nuclear data evaluation that is needed for fundamental nuclear applications.

The correlations between flow harmonics $v_n$ for $n=2$, 3, and 4 and mean transverse momentum $\left[p_{\mathrm{T}}\right]$ in ${}^{129}\mathrm{Xe}+{}^{129}\mathrm{Xe}$ and ${}^{208}\mathrm{Pb}+{}^{208}\mathrm{Pb}$ collisions at $\sqrt{s_{}}=5.44$ and 5.02 TeV, respectively, are measured using charged particles with the ATLAS detector. The correlations are potentially sensitive to the shape and size of the initial geometry, nuclear deformation, and initial momentum anisotropy. The effects from nonflow and centrality fluctuations are minimized, respectively, via a subevent cumulant method and an event-activity selection based on particle production at very forward rapidity. The $v_n\text{−}\left[p_{\mathrm{T}}\right]$ correlations show strong dependencies on centrality, harmonic number $n$, $p_{\mathrm{T}}$, and pseudorapidity range. Current models qualitatively describe the overall centrality- and system-dependent trends but fail to quantitatively reproduce all features of the data. In central collisions, where models generally show good agreement, the $v_2\text{−}\left[p_{\mathrm{T}}\right]$ correlations are sensitive to the triaxiality of the quadruple deformation. Comparison of the model with the $\mathrm{Pb}+\mathrm{Pb}$ and $\mathrm{Xe}+\mathrm{Xe}$ data confirms that the ${}^{129}\mathrm{Xe}$ nucleus is a highly deformed triaxial ellipsoid that has neither a prolate nor oblate shape. This provides strong evidence for a triaxial deformation of the ${}^{129}\mathrm{Xe}$ nucleus from high-energy heavy-ion collisions.

We revisit the unified treatment of low-energy hadronic parity violation espoused by Desplanques, Donoghue, and Holstein to the end of an ab initio treatment of parity violation in low-energy nuclear processes within the standard model. We use our improved effective Hamiltonian and precise nonperturbative assessments of the quark charges of the nucleon within lattice quantum chromodynamics (QCD) to make new assessments of the parity-violating meson-nucleon coupling constants. Comparing with recent, precise measurements of hadronic parity violation in few-body nuclear reactions, we find improved agreement with these experimental results, though some tensions remain. We thus note the broader problem of comparing low-energy constants from nuclear and few-nucleon systems, considering, too, unresolved theoretical issues in connecting an ab initio, effective Hamiltonian approach to chiral effective theories. We note how future experiments and lattice QCD studies could sharpen the emerging picture, promoting the study of hadronic parity violation as a laboratory for testing “end-to-end” theoretical descriptions of weak processes in hadrons and nuclei at low energies.

Based on the Skyrme-Hartree-Fock model (SHF) as well as its extension [the Korea-IBS-Daegu-SKKU (KIDS) model] and the relativistic mean-field (RMF) model, we have studied the constraints on the parameters of the nuclear matter equation of state (EOS) from adopted astrophysical observables using a Bayesian approach. While the masses and radii of neutron stars generally favor a stiff isoscalar EOS and a moderately soft nuclear symmetry energy, model dependence on the constraints is observed and mostly originates from the incorporation of higher-order EOS parameters and differences between relativistic and nonrelativistic models. At twice saturation density, the value of the symmetry energy is constrained to be ${48}_{-11}^{+15}\mathrm{MeV}$ in the standard SHF model, ${48}_{-15}^{+8}\mathrm{MeV}$ in the KIDS model, and ${48}_{-6}^{+5}\mathrm{MeV}$ in the RMF model, around their maximum a posteriori values within $68\%$ confidence intervals. Our study helps to obtain a robust constraint on nuclear matter EOS, and, meanwhile, to understand the model dependence of the results.

A stochastic approach based on four-dimensional Langevin equations has been used to simulate the fission dynamics of the excited compound nuclei ${}^{256}\mathrm{Fm}, {}^{254}\mathrm{Fm}, {}^{224}\mathrm{Th}, {}^{215}\mathrm{Fr}, {}^{213}\mathrm{Fr}, {}^{200}\mathrm{Pb}, {}^{187}\mathrm{Ir}, {}^{172}\mathrm{Yb}, {}^{170}\mathrm{Yb}, {}^{162}\mathrm{Yb}, {}^{142}\mathrm{Ce}$, and ${}^{125}\mathrm{Cs}$ produced in ${}^{16,18}\mathrm{O}+X$ reactions with projectile energies 158.8 and 288 MeV. The effect of nuclear dissipation was investigated in the dynamical simulation of fission process of these nuclei. The average prescission neutron multiplicity, the fission time, the average total kinetic energy of fission fragments, the mass and energy distribution of fission fragments, and the variation of the prescission neutron multiplicity with total kinetic energy of fission fragments have been calculated for these nuclei. The dynamical calculations have taken into account not only three shape collective coordinates introduced on the basis of the “funny hills” shape parameters but also orientation degree of freedom (spin about the symmetry axis), and in the dynamical calculations dissipation generated through the chaos-weighted wall and window friction formula and also the sum of the chaos-weighted wall and window friction formula with the two-body nuclear friction. Furthermore, the effect of dissipation coefficient of $K, {\gamma }_K$, were also considered in the dynamical calculations. Comparison of the theoretical results with the experimental data shows that the experimental data for compound nuclei produced with the projectile energy 158.8 MeV can be reproduced satisfactorily with the results of calculations by using the chaos-weighted wall and window friction formula, although the results of calculations of the average prescission neutron multiplicity, the fission time, and the variation of the pre-scission neutron multiplicity with total kinetic energy of fission fragments lie somewhat below the experimental data for heavy nuclei produced in reactions with projectile energy $E_{\mathrm{lab}}=158.8\mathrm{MeV}$ and also for compound nuclei produced with the projectile energy 288 MeV. It was also shown that for reproducing experimental data for heavy nuclei produced in reactions with projectile energy $E_{\mathrm{lab}}=158.8\mathrm{MeV}$ and also for nuclei produced with projectile energy $E_{\mathrm{lab}}=288\mathrm{MeV}$ is suitable to use the sum of the chaos-weighted wall and window friction formula with the two-body nuclear friction in the Langevin equations. In other words, for simulations of fission dynamics of nuclei at high excitation energies and also for heavy nuclei it is suitable to use the sum of the chaos-weighted wall and window friction formula with the two-body nuclear friction in the Langevin equations.

The ATLAS detector at the Large Hadron Collider has been used to measure jet substructure modification and suppression in $\mathrm{Pb}+\mathrm{Pb}$ collisions at a nucleon–nucleon center-of-mass energy $\sqrt{s_{{}_{NN}}}=5.02\mathrm{TeV}$ in comparison with proton–proton ($pp$) collisions at $\sqrt{s}=5.02\mathrm{TeV}$. The $\mathrm{Pb}+\mathrm{Pb}$ data, collected in 2018, have an integrated luminosity of $1.72{\mathrm{nb}}^{-1}$, while the $pp$ data, collected in 2017, have an integrated luminosity of $260{\mathrm{pb}}^{-1}$. Jets used in this analysis are clustered using the anti-$k_t$ algorithm with a radius parameter $R=0.4$. The jet constituents, defined by both tracking and calorimeter information, are used to determine the angular scale $r_{\mathrm{g}}$ of the first hard splitting inside the jet by reclustering them using the Cambridge–Aachen algorithm and employing the soft-drop grooming technique. The nuclear modification factor, $R_{AA}$, used to characterize jet suppression in $\mathrm{Pb}+\mathrm{Pb}$ collisions, is presented differentially in $r_{\mathrm{g}}$, jet transverse momentum, and in intervals of collision centrality. The $R_{AA}$ value is observed to depend significantly on jet $r_{\mathrm{g}}$. Jets produced with the largest measured $r_{\mathrm{g}}$ are found to be twice as suppressed as those with the smallest $r_{\mathrm{g}}$ in central $\mathrm{Pb}+\mathrm{Pb}$ collisions. The $R_{AA}$ values do not exhibit a strong variation with jet $p_{\mathrm{T}}$ in any of the $r_{\mathrm{g}}$ intervals. The $r_{\mathrm{g}}$ and $p_{\mathrm{T}}$ dependence of jet $R_{AA}$ is qualitatively consistent with a picture of jet quenching arising from coherence and provides the most direct evidence in support of this approach.

We study the fragmentation functions of both pions and kaons in the Field-Feynman recursive model with the extended SU(2) flavor symmetry relations of fragmentation functions and fitting parameters. Parametrizations are determined from a leading-order analysis of HERMES experimental multiplicity data of meson production in semi-inclusive deep inelastic scattering, and uncertainties are estimated with the Hessian method. We compare our results with the experimental data and the analysis results of other parametrizations. The SU(2) flavor symmetry breaking effect of meson fragmentation functions of $ud$ quarks is also discussed, and we show that the fragmentation functions of kaons have a bigger SU(2) flavor symmetry breaking effect of $ud$ quarks than these of pions.