The 50 most-cited articles in Physical Review C, 2023

Generating an ensemble of equations of state that fulfill multimessenger constraints, we statistically determine the properties of dense matter found inside neutron stars (NSs). We calculate the speed of sound and trace anomaly and demonstrate that they are driven towards their conformal values at the center of maximally massive NSs. The local peak of the speed of sound is shown to be located at values of the energy and particle densities, which are consistent with deconfinement and percolation conditions in QCD matter. We also analyze fluctuations of the net-baryon number density in the context of possible remnants of critical behavior. We find that the global maxima of the variance of these fluctuations emerge at densities beyond those found in the interiors of NSs.

Using the recent model-independent determination of the charge-weak form factor difference $\mathrm{\ensuremath{\Delta}}{F}_{\mathrm{CW}}$ in $^{48}\mathrm{Ca}$ and $^{208}\mathrm{Pb}$ by the CREX and PREX-2 collaborations together with some well-determined properties of doubly magic nuclei, we perform Bayesian inference of the symmetry energy ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ and the neutron skin thickness $\mathrm{\ensuremath{\Delta}}{r}_{\mathrm{np}}$ of $^{48}\mathrm{Ca}$ and $^{208}\mathrm{Pb}$ within the Skyrme energy density functional (EDF). We find the inferred ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ and $\mathrm{\ensuremath{\Delta}}{r}_{\mathrm{np}}$ separately from CREX and PREX-2 are compatible with each other at $90%$ C.L., although they are inconsistent at $68.3%$ C.L. with CREX (PREX-2) favoring a very soft (stiff) ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ and rather small (large) $\mathrm{\ensuremath{\Delta}}{r}_{\mathrm{np}}$. By combining the CREX and PREX-2 data, we obtain a soft symmetry energy around saturation density ${\ensuremath{\rho}}_{0}$ and thinner…

New results from the GlueX experiment provide improved cross sections for the photoproduction from the proton of $J/\ensuremath{\psi}$ mesons via the $\ensuremath{\gamma}+p\ensuremath{\rightarrow}J/\ensuremath{\psi}+p$ reaction. Such mesons have charm/anti-charm heavy-quark content. Measurements of this reaction near the kinematic threshold can help constrain aspects of the density distribution of gluons in the proton and how they contribute to the proton mass, under the assumption that $J/\ensuremath{\psi}$ production proceeds primarily through the exchange of gluons with the proton. However, these new measurements suggest contributions in addition to gluon exchange, pointing to the need for further theoretical work and more precise experimental measurements.

It is known that multiple partonic scatterings in high-energy proton-proton ($pp$) collisions must happen in parallel. However, a rigorous parallel scattering formalism, taking energy sharing properly into account, fails to reproduce factorization, which on the other hand is the basis of almost all $pp$ event generators. In addition, binary scaling in nuclear scatterings is badly violated. These problems are usually ``solved'' by simply not considering strictly parallel scatterings, which is not a solution. I will report on new ideas (leading to EPOS4), which allow recovering perfectly factorization, and also binary scaling in $AA$ collisions, in a rigorous unbiased parallel scattering formalism. In this new approach, dynamical saturation scales play a crucial role, and this seems to be the missing piece needed to reconcile parallel scattering with factorization. From a practical point of view, one can compute within the EPOS4 framework parton distribution functions (EPOS PDFs) and use them to compute inclusive $pp$ cross sections. So, for the first time, one may compute inclusive…

We construct a physics-agnostic approach to the neutron star (NS) equation of state (EoS) based on a sound speed model, which connects both low-density information from nuclear theory and high-density constraints from perturbative quantum chromodynamics (pQCD). Using this approach, we study the impact of pQCD calculations on NS EoS that have been constrained by astrophysical observations. We find that pQCD affects the EoS mainly beyond the densities realized in NS. Furthermore, we observe an interesting interplay between pQCD and astrophysical constraints, with pQCD preferring softer EoS for the heaviest NS while recent NICER observations suggest the EoS to be stiffer. We explore the sensitivity of our findings to pQCD uncertainties and study the constraining power of pQCD if future observations of heavy NS were to suggest radii larger than 13 km.

We study low-energy scattering of spin-$\frac{1}{2}$ baryons from the perspective of quantum information science, focusing on the correlation between entanglement minimization and the appearance of accidental symmetries. The baryon transforms as an octet under the $\mathrm{SU}(3)$ flavor symmetry and its interactions below the pion threshold are described by contact operators in an effective field theory (EFT) of QCD. Despite there being 64 channels in the 2-to-2 scattering, only six independent operators in the EFT are predicted by $\mathrm{SU}(3)$. We show that successive entanglement minimization in $\mathrm{SU}(3)$-symmetric channels are correlated with increasingly large emergent symmetries in the EFT. In particular, we identify scattering channels whose entanglement suppression are indicative of emergent $\mathrm{SU}(6), \mathrm{SO}(8), \mathrm{SU}(8)$, and $\mathrm{SU}(16)$ symmetries. We also observe the appearance of non-relativistic conformal invariance in channels with unnaturally large scattering lengths. Improved precision from lattice simulations could help determine…

Neutron stars explore matter at the highest densities in the universe such that their inner cores might undergo a phase transition from hadronic to exotic phases, e.g., quark matter. Such a transition could be associated with nontrivial structures in the density behavior of the speed of sound, such as jumps and sharp peaks. Here, we employ a physics-agnostic approach to model the density dependence of the speed of sound in neutron stars and study to what extent the existence of nontrivial structures can be inferred from existing astrophysical observations of neutron stars. For this, we exhaustively study different equations of state, including as well those with explicit first-order phase transitions. We obtain a large number of different equation of states which reproduce the same astrophysical observations and obey the same physical constraints, such as mechanical stability and causality. Among them, some have nontrivial structures in the sound speed whereas others do not. We conclude that astrophysical information to date do not require the existence of a phase transition to…

We present a new study of jet interactions in the quark-gluon plasma created in high-energy heavy-ion collisions, using a multistage event generator within the jetscape framework. We focus on medium-induced modifications in the rate of inclusive jets and high transverse momentum (high-${p}_{\mathrm{T}}$) hadrons. Scattering-induced jet energy loss is calculated in two stages: a high virtuality stage based on the matter model, in which scattering of highly virtual partons modifies the vacuum radiation pattern, and a second stage at lower jet virtuality based on the lbt model, in which leading partons gain and lose virtuality by scattering and radiation. Coherence effects that reduce the medium-induced emission rate in the matter phase are also included. The trento model is used for initial conditions, and the ($2+1$)dimensional vishnu model is used for viscous hydrodynamic evolution. Jet interactions with the medium are modeled via 2-to-2 scattering with Debye screened potentials, in which the recoiling partons are tracked, hadronized, and included in the jet clustering. Holes left…

We demonstrate that proton and pion flow measurements in heavy-ion collisions at incident energies ranging from 1 to 20 GeV per nucleon in the fixed target frame can be used for an accurate determination of the symmetric nuclear matter equation of state at baryon densities equal 2--4 times nuclear saturation density ${n}_{0}$. We simulate $\mathrm{Au}+\mathrm{Au}$ collisions at these energies using a hadronic transport model with an adjustable vector mean-field potential dependent on baryon density ${n}_{B}$. We show that the mean field can be parametrized to reproduce a given density dependence of the speed of sound at zero temperature ${c}_{s}^{2}({n}_{B},T=0)$, which we vary independently in multiple density intervals to probe the differential sensitivity of heavy-ion observables to the equation of state at these specific densities. Recent flow data from the STAR experiment at the center-of-mass energies $\sqrt{{s}_{NN}}={3.0,4.5}\phantom{\rule{4pt}{0ex}}\mathrm{GeV}$ can be described by our model, and a Bayesian analysis of these data indicates a hard equation of state at…

Halos and changes of nuclear magicities have been extensively investigated in exotic nuclei during past decades. The newly discovered $^{39}\mathrm{Na}$ with the neutron number $N=28$ provides a new platform to explore such novel phenomena near the neutron dripline of the sodium isotopic chain. We study the shell property and the possible halo structure in $^{39}\mathrm{Na}$ within the deformed relativistic Hartree-Bogoliubov theory in continuum. It is found that the lowering of $2p$ orbitals in the spherical limit results in the collapse of the $N=28$ shell closure in $^{39}\mathrm{Na}$, and a well-deformed ground state is established. The pairing correlations and the mixing of $pf$ components driven by deformation lead to the occupation of weakly bound or continuum $p$-wave neutron orbitals. An oblate halo is therefore formed around the prolate core in $^{39,41}\mathrm{Na}$, making $^{39}\mathrm{Na}$ a single nucleus with the coexistence of several exotic structures, including the quenched $N=28$ shell closure, Borromean structure, deformed halo, and shape decoupling. The…

All recent analyses of heavy-ion data that extract information about the transport properties of excited strongly interacting matter use Bayesian techniques to fit parameters of functional forms motivated by physical insight. These explicit parameterizations may introduce undesired long-range correlations between different regions of parameter space. This paper develops an information field approach to avoid an explicit functional parameterization and obtain a global Bayesian inference of the jet transport coefficient $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{q}$ as a function of the temperature.

The need to reconcile our understanding of the behavior of hadronic matter across a wide range of densities, especially at the time when data from multimessenger observations and novel experimental facilities are flooding in, has provided new challenges to the nuclear models. Particularly, the density dependence of the isovector channel of the nuclear energy functionals seems hard to pin down if experiments like PREX-II (or PREX) and CREX are required to be taken on the same footing. We put to test this anomaly in a semiagnostic modeling technique by performing a full Bayesian analysis of static properties of neutron stars, together with global properties of nuclei as binding energy, charge radii and neutron skin calculated at the semiclassical level. Our results show that the interplay between bulk and surface properties, and the importance of high-order empirical parameters that effectively decouple the subsaturation and the supersaturation density regime, might partially explain the tension between the different measurements and observations. If the surface behaviors, however,…

In relativistic heavy-ion collisions, a global spin polarization, ${P}_{\mathrm{H}}$, of $\mathrm{\ensuremath{\Lambda}}$ and $\overline{\mathrm{\ensuremath{\Lambda}}}$ hyperons along the direction of the system angular momentum was discovered and measured across a broad range of collision energies and demonstrated a trend of increasing ${P}_{\mathrm{H}}$ with decreasing $\sqrt{{s}_{NN}}$. A splitting between $\mathrm{\ensuremath{\Lambda}}$ and $\overline{\mathrm{\ensuremath{\Lambda}}}$ polarization may be possible due to their different magnetic moments in a late-stage magnetic field sustained by the quark-gluon plasma which is formed in the collision. The results presented in this study find no significant splitting at the collision energies of $\sqrt{{s}_{NN}}=19.6$ and 27 GeV in the BNL Relativistic Heavy Ion Collisions Beam Energy Scan Phase II using the STAR detector, with an upper limit of ${P}_{\overline{\mathrm{\ensuremath{\Lambda}}}}\ensuremath{-}{P}_{\mathrm{\ensuremath{\Lambda}}}<0.24$% and…

The correlations between flow harmonics ${v}_{n}$ for $n=2$, 3, and 4 and mean transverse momentum $[{p}_{\mathrm{T}}]$ 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 ${v}_{n}\text{\ensuremath{-}}[{p}_{\mathrm{T}}]$ 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…

The $^{232}\mathrm{Th}+^{48}\mathrm{Ca}$ reaction has been studied at the gas-filled separator DGFRS-2 online to the cyclotron DC280 at the SHE Factory at JINR. Three new nuclides were synthesized for the first time: a spontaneously fissioning (SF) $^{268}\mathrm{Sg}$ with the half-life ${T}_{\mathrm{SF}}=13\begin{array}{c}+17\\ \ensuremath{-}4\end{array}$ s; an \ensuremath{\alpha} decaying $^{272}\mathrm{Hs}$ with ${T}_{\ensuremath{\alpha}}=0.16\begin{array}{c}+0.19\\ \ensuremath{-}0.06\end{array}$ s and ${E}_{\ensuremath{\alpha}}=9.63\ifmmode\pm\else\textpm\fi{}0.02\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$; and $^{276}\mathrm{Ds}$ with ${T}_{1/2}=0.15\begin{array}{c}+0.10\\ \ensuremath{-}0.04\end{array}$ ms, ${E}_{\ensuremath{\alpha}}=10.75\ifmmode\pm\else\textpm\fi{}0.03\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$, and an SF branch of 57%. The decay properties of these nuclei are in agreement with the systematics of experimental partial half-lives and \ensuremath{\alpha}-decay energies of heavy known nuclei, as well as spontaneous-fission half-lives. The cross sections of the…

In high-energy heavy-ion collisions, the initial condition of the produced quark-gluon plasma (QGP) and its evolution are sensitive to collective nuclear structure parameters describing the shape and radial profiles of the nuclei. We find a general scaling relation between these parameters and many experimental observables such as elliptic flow, triangular flow, and particle multiplicity distribution. In particular, the ratios of observables between two isobar systems depend only on the differences of these parameters, but not on the details of the final state interactions, hence offering a new way to constrain the QGP initial condition. Using this scaling relation, we show how the structure parameters of ${}_{44}^{96}\mathrm{Ru}$ and ${}_{40}^{96}\mathrm{Zr}$ conspire to produce the rich centrality dependences of these ratios, as measured by the STAR Collaboration. Our scaling approach demonstrates that isobar collisions are a precision tool to probe the initial condition of heavy-ion collisions, as well as the collective nuclear structures, including the neutron skin, of the…

We recently introduced new concepts, implemented in EPOS4, which allows us to consistently accommodate factorization and saturation in high-energy proton-proton and nucleus-nucleus collisions in a rigorous parallel scattering framework. EPOS4 has a modular structure and in this paper, we present in detail how the ``single scattering module'' (the main EPOS4 building block) is related to perturbative QCD and how these calculations are performed, with particular care being devoted to heavy flavor contributions. We discuss similarities and differences compared to the usual pQCD approach based on factorization.

Optical-model potentials (OMPs) continue to play a key role in nuclear reaction calculations. However, the uncertainty of phenomenological OMPs in widespread use---inherent to any parametric model trained on data---has not been fully characterized, and its impact on downstream users of OMPs remains unclear. Here we assign well-calibrated uncertainties for two representative global OMPs, those of Koning-Delaroche and Chapel Hill '89, using Markov-chain Monte Carlo for parameter inference. By comparing the canonical versions of these OMPs against the experimental data originally used to constrain them, we show how a lack of outlier rejection and a systematic underestimation of experimental uncertainties contributes to bias of, and overconfidence in, best-fit parameter values. Our updated, uncertainty-quantified versions of these OMPs address these issues and yield complete covariance information for potential parameters. Scattering predictions generated from our ensembles show improved performance both against the original training corpora of experimental data and against a new…

Two formulations of relativistic hydrodynamics of particles with spin 1/2 are compared. The first approach, dubbed the canonical one, uses expressions for the energy-momentum and spin tensors that have properties that follow a direct application of Noether's theorem, which yields a totally antisymmetric spin tensor. The other one is based on a simplified form of the spin tensor and is commonly used in the current literature under the name of a phenomenological approach. We show that these two frameworks are equivalent, i.e., they can be directly connected by a suitably defined pseudogauge transformation, only if the first framework is initially improved by a suitable modification of the energy-momentum tensor (addition of a divergence-free term that cannot be interpreted as a pseudogauge). Our analysis uses arguments related to the positivity of entropy production. The latter turns out to be equivalent for the improved canonical and phenomenological frameworks.

Transverse momentum (${p}_{\ensuremath{\perp}}$) generation in relativistic heavy-ion collisions is sensitive to the initial geometry and the final-state bulk evolution. We demonstrate with hydrodynamic calculations that the mean ${p}_{\ensuremath{\perp}}$ ratio (${R}_{\ensuremath{\langle}{p}_{\ensuremath{\perp}}\ensuremath{\rangle}}$) between the highly similar isobar $_{44}^{96}\mathrm{Ru}+_{44}^{96}\mathrm{Ru}$ and $_{40}^{96}\mathrm{Zr}+_{40}^{96}\mathrm{Zr}$ collisions is insensitive to the bulk evolution and remains sensitive to the small difference in the initial nuclear structure (neutron skin and deformation) between the Ru and Zr nuclei. We further find that nuclear deformation can produce an anticorrelation between ${R}_{\ensuremath{\langle}{p}_{\ensuremath{\perp}}\ensuremath{\rangle}}$ and eccentricity (or elliptic flow) in central collisions. These findings suggest that the ${R}_{\ensuremath{\langle}{p}_{\ensuremath{\perp}}\ensuremath{\rangle}}$ between the isobar systems can be used to measure the neutron skin thickness and deformation parameters, which can, in turn,…

There is no unique and widely accepted definition of the complexity measure (CM) of a many-fermion wave function in the presence of interactions. The simplest many-fermion wave function is a Slater determinant. In shell-model or configuration interaction (CI) and other related methods, the state is represented as a superposition of a large number of Slater determinants, which in the case of CI calculations reaches about 20 billion terms [Johnson, arXiv:1809.07869]. Although in practice this number has been used as a CM for decades, it is ill defined: it is not unique, and it depends on the particular type and the number of single-particle wave functions used to construct the Slater determinants. The canonical wave functions and/or natural orbitals [L\"owdin, Adv. Phys. 5, 1 (1956); L\"owdin and Shull, Phys. Rev. 101, 1730 (1956); Bardeen et al., Phys. Rev. 108, 1175 (1957); N. N. Bogoljubov, Il Nuovo Cimento 7, 794 (1958); Valatin, Il Nuovo Cimento 7, 843 (1958); de Gennes, Superconductivity of Metals and Alloys (CRC Press, Boca Raton, FL, 1999); Ring and Schuck, The Nuclear…

We present ($3+1$)-dimensional [($3+1$)D] dynamical simulations of asymmetric nuclear collisions at the BNL Relativistic Heavy Ion Collider (RHIC). Employing a dynamical initial state model coupled to ($3+1$)D viscous relativistic hydrodynamics, we explore the rapidity dependence of anisotropic flow in the RHIC small system scan at 200 GeV center-of-mass energy. We calibrate parameters to describe central $^{3}\mathrm{He}+\mathrm{Au}$ collisions and make extrapolations to $d+\mathrm{Au}$ and $p+\mathrm{Au}$ collisions. Our calculations demonstrate that approximately 50% of the ${v}_{3}({p}_{T})$ difference between the measurements by the STAR and PHENIX Collaborations can be explained by the use of reference flow vectors from different rapidity regions. This emphasizes the importance of longitudinal flow decorrelation for anisotropic flow measurements in asymmetric nuclear collisions, and the need for ($3+1$)D simulations. We also present results for the beam energy dependence of particle spectra and anisotropic flow in $d+\mathrm{Au}$ collisions.

Background: Quantum simulations offer the potential to predict the structure and dynamics of nuclear many-body systems that are beyond the capabilities of classical computing. Generally, preparing the ground state of strongly interacting many-body systems relevant to nuclear physics is, however, inefficient, even using ideal quantum computers. In addition, currently available noisy intermediate-scale quantum (NISQ) era quantum devices possess modest numbers of qubits, limiting the size of quantum many-body systems that can be simulated. In this context, a reformulation of the quantum many-body problems using truncated model spaces and Hamiltonians is desirable to make them more amenable to near-term quantum computers. The importance of symmetries in low-energy theories, including effective field theories (EFTs), lattice quantum chromodynamics (QCD), and effective model spaces for nuclear systems, in particular their interplay with the reduction of active Hilbert spaces, is well known. Lesser known is the fact that the noncommutivity of some symmetries and truncations of the model…

We study the rapidity and azimuthal angle dependences of the global spin alignment ${\ensuremath{\rho}}_{00}$ for $\ensuremath{\phi}$ mesons with respect to the reaction plane in $\mathrm{Au}+\mathrm{Au}$ collisions at the BNL Relativistic Heavy Ion Collider by the relativistic coalescence model in the spin transport theory. The global spin alignment of $\ensuremath{\phi}$ mesons arises from local fluctuations of strong force fields whose values are extracted from the STAR's data. The calculated results show that ${\ensuremath{\rho}}_{00}<1/3$ at the rapidity $Y=0$, and then it increases with rapidity and becomes ${\ensuremath{\rho}}_{00}>1/3$ at $Y=1$. Such a rapidity dependence is dominated by the relative motion of the $\ensuremath{\phi}$ meson in the bulk matter. We also give a prediction for the azimuthal angle dependence of ${\ensuremath{\rho}}_{00}$ at different rapidities.

We develop a kinetic approach to the production of light nuclei up to mass number $A\phantom{\rule{4pt}{0ex}}\ensuremath{\leqslant}\phantom{\rule{4pt}{0ex}}4$ in intermediate-energy heavy-ion collisions by including them as dynamic degrees of freedom. The conversions between nucleons and light nuclei during the collisions are incorporated dynamically via the breakup of light nuclei by a nucleon and their reverse reactions. We also include the Mott effect on light nuclei; i.e., a light nucleus will no longer be bound if the phase-space density of its surrounding nucleons is too large. With this kinetic approach, we obtain a reasonable description of the measured yields of light nuclei in central $\mathrm{Au}+\mathrm{Au}$ collisions at energies of $0.25A\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$--$1.0A\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$ by the FOPI Collaboration. Our study also indicates that the observed enhancement of the $\ensuremath{\alpha}$-particle yield at low incident energies can be attributed to a weaker Mott effect on the $\ensuremath{\alpha}$ particle, which makes it…

We study two-neutrino ($2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) and neutrinoless double-$\ensuremath{\beta}$ ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) decays in the nuclear shell model and proton-neutron quasiparticle random-phase approximation (pnQRPA) frameworks. Calculating the decay half-life of several dozens of nuclei ranging from calcium to xenon with the shell model, and of $\ensuremath{\beta}\ensuremath{\beta}$ emitters with a wide range of proton-neutron pairing strengths in the pnQRPA, we observe good linear correlations between $2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$- and $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay nuclear matrix elements for both methods. We then combine the correlations with measured $2\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay half-lives to predict $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay matrix elements with theoretical uncertainties based on our systematic calculations. Our results include two-body currents and the short-range…

Various models of the QCD phase diagram favor a first-order phase transition to quark-gluon plasma, and therefore a critical endpoint which could manifest itself in measurable fluctuations and correlations. The authors report measurements of the moments of the net proton multiplicity fluctuations (cumulants) and correlation functions from the RHIC beam energy scan. They establish that at $\sqrt{{s}_{N\phantom{\rule{0}{0ex}}N}}=3$ GeV the produced system is dominated by hadronic rather than thermal interactions. This puts a limit on the search for the elusive critical point in the QCD phase diagram to energies higher than 3 GeV.

We study entanglement entropies between the single-particle states of the hole space and its complement in nuclear systems. Analytical results based on the coupled-cluster method show that entanglement entropies are proportional to the particle number fluctuation and the depletion number of the hole space for sufficiently weak interactions. General arguments also suggest that the entanglement entropy in nuclear systems fulfills a volume instead of an area law. We test and confirm these results by computing entanglement entropies of the pairing model and neutron matter, and the depletion number of finite nuclei.

$\ensuremath{\alpha}$ decay serves as an important probe for the studies of unstable nuclei. This paper proposes an approach combining the sophisticated $\ensuremath{\alpha}$-decay model and Bayesian neural network (BNN) to improve the prediction accuracy of $\ensuremath{\alpha}$-decay half-lives. The global and extrapolated analyses show that the BNN method can improve the description of model-based predictions of $\ensuremath{\alpha}$ decay. In our calculation, the experimental decay energies ${Q}_{\ensuremath{\alpha}}$ are used to obtain the accurate $\ensuremath{\alpha}$-decay penetration probability, which indicates that the improvements come from the corrections of $\ensuremath{\alpha}$-cluster preformation factors. Further analyzing $\ensuremath{\alpha}$-decay half-lives of nuclide chains shows that the shell structure effect can be well introduced into estimations of $\ensuremath{\alpha}$-cluster preformation factors by utilizing the BNN. The studies of this paper provide an effective way to predict the $\ensuremath{\alpha}$-decay half-lives of unknown nuclei.

For quantum many-body systems with short-range correlations (SRCs), the intimate relationship between their magnitude, the behavior of the single-particle occupation probabilities at momenta larger than the Fermi momentum, and the entanglement entropy is a new qualitative aspect not studied and exploited yet. A large body of recent condensed matter studies indicates that the time evolution of the entanglement entropy describes the nonequilibrium dynamics of isolated and strongly interacting many-body systems, in a manner similar to the Boltzmann entropy, which is strictly defined for dilute and weakly interacting many-body systems. Both theoretical and experimental studies in nuclei and cold atomic gases have shown that the fermion momentum distribution has a generic behavior $n(k)=C/{k}^{4}$ at momenta larger than the Fermi momentum, due to the presence of SRCs, with approximately 20% of the particles having momenta larger than the Fermi momentum. The presence of the long momentum tails in the presence of SRCs changes the textbook relation between the single-particle kinetic energy…

A microscopic self-consistent triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc), which simultaneously takes into account the triaxiality and pairing correlations as well as continuum effects, is established and applied to explore the novel halo phenomenon in aluminum isotopes. The experimental proton drip line and the available data of neutron separation energies and charge radii are reproduced well without any free parameters. The neutron-richest odd-odd aluminum isotope observed so far, $^{42}\mathrm{Al}$, is predicted to be triaxially deformed with $\ensuremath{\beta}=0.35$ and $\ensuremath{\gamma}={42}^{\ensuremath{\circ}}$. Its one-neutron separation energy is predicted to be 0.68 MeV, in agreement with the AME2020, and the neutron rms radius is 3.94 fm, remarkably larger than the empirical value. The density distribution of the valance neutron, which extends much farther in space than the core, suggests a possible neutron halo in $^{42}\mathrm{Al}$. The dominant components responsible for the spatial extension of the halo are revealed by the single-neutron…

Three-nucleon (3N) interactions are key for an accurate solution of the nuclear many-body problem. However, fully taking into account 3N forces constitutes a computational challenge and hence approximate treatments are commonly employed. The method of normal ordering has proven to be a powerful tool that allows to systematically include 3N interactions in an efficient way, but traditional normal-ordering frameworks require the representation of 3N interactions in a large single-particle basis, typically necessitating a truncation of 3N matrix elements. While this truncation has only a minor impact for light and medium-mass nuclei, its effects become sizable for heavier systems and hence limit the scope of ab initio calculations. In this work, we present a novel normal-ordering framework that allows to circumvent this limitation by performing the normal ordering directly in a Jacobi basis. We discuss in detail the new framework, benchmark it against established results, and present calculations for ground-state energies and charge radii of heavy nuclei, such as $^{132}\mathrm{Sn}$…

A modified version of the density dependent covariant density-functional model proposed in [Astrophys. J. 930, 17 (2022)] is employed in a Bayesian analysis to determine the equation of state (EOS) of dense matter with nucleonic degrees of freedom. Various constraints from nuclear physics and microscopic calculations of pure neutron matter (PNM) along with a lower bound on the maximum mass of neutron stars (NSs) are imposed on the EOS models to investigate the effectiveness of progressive incorporation of the constraints, their compatibility as well as correlations among parameters of nuclear matter and properties of NSs. Our results include the different roles played by pressure and energy per particle of PNM in constraining the isovector behavior of nuclear matter; tension with the values of Dirac effective mass extracted from spin-orbit splitting; correlations between the radius of the canonical mass NS and second- and third-order coefficients in the Taylor expansion of energy per particle as a function of density; correlation between the central pressure of the maximum mass…

The understanding of the mechanisms for the production of weakly bound clusters, such as a deuteron $d$, in heavy-ion reactions at mid-rapidity is presently one of the challenging problems which is also known as the ``ice in a fire'' puzzle. In this study we investigate the dynamical formation of deuterons within the parton-hadron quantum molecular dynamics (PHQMD) microscopic transport approach and advance two microscopic production mechanisms to describe deuterons in heavy-ion collisions from energies available at the GSI Schwerionensynchrotron (SIS) to those at the BNL Relativistic Heavy Ion Collider (RHIC): kinetic production by hadronic reactions and potential production by the attractive potential between nucleons. Differently from other studies, for the ``kinetic'' deuterons we employ the full isospin decomposition of the various $\ensuremath{\pi}NN\ensuremath{\leftrightarrow}\ensuremath{\pi}d, NNN\ensuremath{\leftrightarrow}Nd$ channels and take into account the finite-size properties of the deuteron by means of an excluded volume condition in coordinate space and by the…

The hot fusion reaction ${}^{48}$C + ${}^{238}$U is studied with time-dependent Hartree-Fock theory in combination with coupled-channels and fusion-by-diffusion models. The authors find that the fusion probability is strongly dependent on the orientation of the ${}^{238}$U nucleus, with the probability being greatest for the tip collision orientation. This understanding will be applied in the future to determine optimal target and projectile combinations for the synthesis of elements $Z=119$ and 120.

The ATLAS detector at the Large Hadron Collider has been used to measure jet substructure modification and suppression in Pb+Pb collisions at a nucleon-nucleon center-of-mass energy √ s NN = 5.02 TeV in comparison with proton-proton (pp) collisions at √ s = 5.02 TeV.The Pb+Pb data, collected in 2018, have an integrated luminosity of 1.72 nb -1 , while the pp data, collected in 2017, have an integrated luminosity of 260 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 g of the first hard splitting inside the jet by reclustering them using the Cambridge-Aachen algorithm and employing the softdrop grooming technique.The nuclear modification factor, R AA , used to characterize jet suppression in Pb+Pb collisions, is presented differentially in r g , jet transverse momentum, and in intervals of collision centrality.The R AA value is observed to depend significantly on jet r g .Jets produced with the largest…

Predicting the structure of quantum many-body systems from the first principles of quantum mechanics is a common challenge in physics, chemistry, and material science. Deep machine learning has proven to be a powerful tool for solving condensed matter and chemistry problems, while for atomic nuclei it is still quite challenging because of the complicated nucleon-nucleon interactions, which strongly couple the spatial, spin, and isospin degrees of freedom. By combining essential physics of the nuclear wave functions and the strong expressive power of artificial neural networks, we develop FeynmanNet, a deep-learning variational quantum Monte Carlo approach for ab initio nuclear structure. We show that FeynmanNet can provide very accurate solutions of ground-state energies and wave functions for $^{4}\mathrm{He}, ^{6}\mathrm{Li}$, and even up to $^{16}\mathrm{O}$ as emerging from the leading-order and next-to-leading-order Hamiltonians of pionless effective field theory. Compared to the conventional diffusion Monte Carlo approaches, which suffer from the severe inherent fermion-sign…

The deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) is employed to study the ground-state properties of Kr and Sr isotopes. Based on the constrained DRHBc calculations, it is found that Kr and Sr isotopes with $N=50$ are spherical, while the nuclei just away from $N=50$ generally have soft potential energy curves. Further moving along the isotopic chains in both neutron-rich and neutron-deficient directions, there are generally two minima at oblate and prolate sides for nuclear potential energy curves, where possible candidates for shape coexistence are found. The dynamical correlations are crucial to describe the properties of nuclei with soft potential energy curves or shape coexistence, e.g., the binding energies, two-neutron separation energies, deformations, and charge radii, which are considered with the two-dimensional collective Hamiltonian method. In addition, the constrained DRHBc calculations would be helpful to distinguish the oblate or prolate shape for the nuclei with deformation $|{\ensuremath{\beta}}_{2}|\ensuremath{\gtrsim}0.3$ by combining with…

We address the question of the role of low-energy nuclear physics data in constraining neutron star global properties, e.g., masses, radii, angular momentum, and tidal deformability, in the absence of a phase transition in dense matter. To do so, we assess the capacity of 415 relativistic mean field and nonrelativistic Skyrme-type interactions to reproduce the ground state binding energies, the charge radii, and the giant monopole resonances of a set of spherical nuclei. The interactions are classified according to their ability to describe these characteristics, and we show that a tight correlation between the symmetry energy and its slope is obtained provided that $N=Z$ and $N\ensuremath{\ne}Z$ nuclei are described with the same accuracy (mainly driven by the charge radius data). By additionally imposing the constraints from isobaric analog states and neutron skin radius in $^{208}\mathrm{Pb}$, we obtain the following estimates: ${E}_{\mathrm{sym},2}=31.8\ifmmode\pm\else\textpm\fi{}0.7$ MeV and ${L}_{\mathrm{sym},2}=58.1\ifmmode\pm\else\textpm\fi{}9.0$ MeV. We then analyze…

Using a ($3+1$)-dimensional hybrid framework with parametric initial conditions, we study the rapidity-dependent directed flow ${v}_{1}(y)$ of identified particles, including pions, kaons, protons, and lambdas in heavy-ion collisions. Cases involving $\mathrm{Au}+\mathrm{Au}$ collisions are considered, performed at $\sqrt{{s}_{NN}}$ ranging from 7.7 to 200 GeV. The dynamics in the beam direction is constrained using the measured pseudorapidity distribution of charged particles and the net proton rapidity distribution. Within this framework, the directed flow of mesons is driven by the sideward pressure gradient from the tilted source, and that of baryons mainly due to the initial asymmetric baryon distribution with respect to the beam axis driven by the transverse expansion. Our approach successfully reproduces the rapidity- and beam energy-dependence of ${v}_{1}$ for both mesons and baryons. We find that the ${v}_{1}(y)$ of baryons has strong constraining power on the initial baryon stopping, and together with that of mesons, the directed flow probes the equation of state of the…

The entanglement properties of neutron-proton scattering are investigated using a measure that counts the number of entangled pairs produced by the action of a scattering operator on a given initial neutron-proton state. All phase shifts relevant for scattering at laboratory energies up to 350 MeV are used. Entanglement is found to depend strongly on the initial state. Entanglement is maximized in very low energy scattering if the initial spin state is $|\ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\rangle}$, but not if the initial state is $|\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\rangle}$. At such energies the Hamiltonian obeys Wigner SU(4) symmetry, and an entanglement maximum is a sign of that symmetry. At higher energies the angular dependence of entanglement is strong and the entanglement is large for many scattering angles. The tensor force is shown to play a significant role in producing entanglement at laboratory kinetic energies greater than about 50 MeV.

The nuclear structure orbital entanglement entropy of short range correlation (SRC) is calculated based on the nuclear scale separation, specifically, the entanglement between the SRC orbitals and the rest of the system. It should be stressed that this is a single nucleon and not a pair entanglement entropy between the proton and neutron. The entanglement arises from the probability for a nucleon to occupy a momentum state above the Fermi momentum. The momentum space of the nucleus separates into two parts such that nucleons can occupy the mean-field part of the wave function, i.e., the Fermi sea (FS) and separately the high-momentum SRC part. The orbital entropy obtained is between these two parts where essentially two momentum subspaces are defined, one containing all the low momentum FS states and the other containing the high-momentum part as a SRC ``orbital'' state. For the calculation of the decoupling of low and high momenta which was established by the similarity normalization group the SRC is employed and viewed as a further orbital which can be multiply occupied. Since the…

Isospin-symmetry breaking is responsible for the energy difference of excited states in mirror nuclei. It also influences the coefficient of the isobaric multiplet mass equation. In the present work, we extensively investigate isospin-symmetry breaking in medium-mass nuclei within ab initio frameworks. For this, we employ the ab initio valence-space in-medium similarity renormalization group approach, in which charge-symmetry and charge-independence breakings are included in the adopted nuclear force. The mirror energies of $sd$- and $pf$-shell nuclei are computed for that matter. The effects of single-particle states on weakly bound and unbound nuclear states, especially those of the $s$ wave, are discussed. Predictions are also made concerning proton drip-line nuclei bearing large mirror energy difference. Finally, the coefficient of the isobaric multiplet mass equation in $T=1/2$ and $T=1$ isospin multiplets for $A=18$ to $A=76$ is calculated.

Nuclear reactors are the most copious human-made source of electron antineutrinos (${\overline{\ensuremath{\nu}}}_{e}$) on Earth; yet, determining their flux and spectrum with accuracy remains a considerable challenge. In fact, measurements of the antineutrino flux from reactors have shown a deficit with respect to predictions, which has become known as the reactor antineutrino anomaly. This work combines a careful analysis of up-to-date nuclear decay data with advanced theoretical corrections to the $V$-$A$ theory of $\ensuremath{\beta}$ decay to produce, for the first time, a flux prediction with a comprehensive uncertainty budget. This new prediction achieves a better agreement with existing experimental neutrino data and methodically pins down points for improvements. It will likely stimulate targeted research to check and improve the experimental inputs, with potentially wide-ranging impact, from weak-interaction physics to many aspects of nuclear reactor science and technology.

Background: Single-charge-exchange reactions are appropriate tools to study the nuclear response to one-particle/one-hole isospin probes, gaining additional interest from the connection to beta decay. This analogy has been recently extended to second order, connecting double-charge-exchange reactions and double beta decays. Nowadays, the availability of powerful experimental setups and advanced nuclear theories and models allows one to access precious information on key nuclear structure aspects embedded in the widely sought neutrinoless double beta decay.Purpose: We intend to bring to light the main nuclear structure and reaction features involved in the $^{18}\mathrm{O}+^{12}\mathrm{C}$ collision at 275 MeV incident energy. In this paper, the main focus is on the role of the initial- and final-state interactions in the overall reaction dynamics and on the single-particle nuclear structure properties accessed via the study of single-nucleon transfer reactions. Forthcoming articles will be devoted to go into the details of the response to one- and two-particle/hole isospin…

To exploit the potential of deep learning (DL) in $\ensuremath{\alpha}$-decay studies, we refocus on the essence of DL, which is a nonlinear input-output mapping with a hierarchical learning process. Here, instead of using the residual between experimental data and the calculation, the idea of training DL directly by experimental $\ensuremath{\alpha}$-decay half-life is used. The Levenberg-Marquardt backpropagation algorithm is utilized for fixing free parameters of the mapping. A $\mathcal{K}$-fold cross-validation method is introduced to avoid overfitting and improve the generalization performance of DL, as well as to determine hyperparameters effectively. We find that DL results with both three-dimensional ${Z,A,{Q}_{\ensuremath{\alpha}}}$ and four-dimensional ${Z,A,{Q}_{\ensuremath{\alpha}},l}$ input vectors achieve an impressive accuracy that matches or even exceeds the traditional models. Especially, DL realizes an efficient extraction of the pertinent shell and odd-even staggering effects of half-life solely from the characteristics of ${Q}_{\ensuremath{\alpha}}$ values. On…

Precision mass measurements of neutron-rich rhodium isotopes have been performed at the JYFLTRAP Penning trap mass spectrometer at the Ion Guide Isotope Separator On-Line (IGISOL) facility. We report results on ground- and isomeric-state masses in $^{110,112,114,116,118}\mathrm{Rh}$ and the very first mass measurement of $^{120}\mathrm{Rh}$. The isomeric states were separated and measured for the first time using the phase-imaging ion-cyclotron-resonance (PI-ICR) technique. For $^{112}\mathrm{Rh}$, we also report new half-lives for both the ground state and the isomer. The results are compared to theoretical predictions using the BSkG1 mass model and discussed in terms of triaxial deformation.

The recent observation of the object HESS J1731-347 suggests the existence of a very light and very compact neutron star, which is a challenge for commonly used equations of state for dense matter. In this work we present a relativistic mean-field model enriched with isovector and isoscalar meson crossing terms. These interactions dominate the behavior of the symmetry energy and account for the small radius. The proposed model fulfills the recent constraints concerning the symmetry energy slope and the state-of-the-art compact star constraints derived from the NICER measurements of the pulsars PSR $\mathrm{J}0030+0451$ and PSR $\mathrm{J}0740+6620$, as well as from the GW170817 event and its associated electromagnetic counterparts AT2017gfo/GRB170817A.

We sample over 500 relativistic mean-field theories constrained by chiral effective-field theory and properties of isospin-symmetric nuclear matter and test them against known stellar structure constraints. This includes a recent mass and radius measurement of a compact object in supernova remnant HESS J1731-347, with an unusually low mass of $M=0.{77}_{\ensuremath{-}0.17}^{+0.20}{M}_{\ensuremath{\bigodot}}$ and a compact radius of $R=10.{4}_{\ensuremath{-}0.78}^{+0.86}$ km. We show that none of the sampled nuclear models meet all constraints at the $68%$ credibility level, but that hybrid equations of state with a quark-matter inner core and nuclear outer core easily can. This indicates a tension between astrophysical constraints and low-energy nuclear theory.

The measurement of the production of deuterons, tritons and $^{3}\mathrm{He}$ and their antiparticles in Pb-Pb collisions at $\sqrt{{s}_{NN}}=5.02\phantom{\rule{4pt}{0ex}}\mathrm{TeV}$ is presented in this article. The measurements are carried out at midrapidity $(|y|< 0.5)$ as a function of collision centrality using the ALICE detector. The ${p}_{\mathrm{T}}$-integrated yields, the coalescence parameters and the ratios to protons and antiprotons are reported and compared with nucleosynthesis models. The comparison of these results in different collision systems at different center-of-mass collision energies reveals a suppression of nucleus production in small systems. In the Statistical Hadronisation Model framework, this can be explained by a small correlation volume where the baryon number is conserved, as already shown in previous fluctuation analyses. However, a different size of the correlation volume is required to describe the proton yields in the same data sets. The coalescence model can describe this suppression by the fact that the wave functions of the nuclei are large…