The 50 most-cited articles in Physical Review C, 2022

The chiral magnetic effect (CME) is predicted to occur as a consequence of a local violation of $\mathcal{P}$ and $\mathcal{C}P$ symmetries of the strong interaction amidst a strong electromagnetic field generated in relativistic heavy-ion collisions. Experimental manifestation of the CME involves a separation of positively and negatively charged hadrons along the direction of the magnetic field. Previous measurements of the CME-sensitive charge-separation observables remain inconclusive because of large background contributions. To better control the influence of signal and backgrounds, the STAR Collaboration performed a blind analysis of a large data sample of approximately 3.8 billion isobar collisions of $_{44}^{96}\mathrm{Ru}+_{44}^{96}\mathrm{Ru}$ and $_{40}^{96}\mathrm{Zr}+_{40}^{96}\mathrm{Zr}$ at $\sqrt{{s}_{{}_{NN}}}=200$ GeV. Prior to the blind analysis, the CME signatures are predefined as a significant excess of the CME-sensitive observables in $\mathrm{Ru}+\mathrm{Ru}$ collisions over those in $\mathrm{Zr}+\mathrm{Zr}$ collisions, owing to a larger magnetic field in…

We propose a novel storage scheme for three-nucleon (3N) interaction matrix elements relevant for the normal-ordered two-body approximation used extensively in ab initio calculations of atomic nuclei. This scheme reduces the required memory by approximately two orders of magnitude, which allows the generation of 3N interaction matrix elements with the standard truncation of ${E}_{3\mathrm{max}}=28$, well beyond the previous limit of 18. We demonstrate that this is sufficient to obtain the ground-state energy of $^{132}\mathrm{Sn}$ converged to within a few MeV with respect to the ${E}_{3\mathrm{max}}$ truncation. In addition, we study the asymptotic convergence behavior and perform extrapolations to the un-truncated limit. Finally, we investigate the impact of truncations made when evolving free-space 3N interactions with the similarity renormalization group. We find that the contribution of blocks with angular momentum ${J}_{\mathrm{rel}}>9/2$ to the ground-state energy is dominated by a basis-truncation artifact, which vanishes in the large-space limit, so these computationally…

Nuclear masses are predicted with the Bayesian neural networks by learning the mass surface of even-even nuclei and the correlation energies to their neighboring nuclei. By keeping the known physics in various sophisticated mass models and performing the delicate design of neural networks, the proposed Bayesian machine learning mass model achieves an accuracy of $84\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$, which crosses the accuracy threshold of the $100\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$ in the experimentally known region. It is also demonstrated the corresponding uncertainties of mass predictions are properly evaluated, while the uncertainties increase by about $50\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$ each step along the isotopic chains towards the unknown region. The shell structures in the known region are well described and several important features in the unknown region are predicted, such as the new magic numbers around $N=40$, the robustness of $N=82$ shell, the quenching of $N=126$ shell, and the smooth separation energies around $N=104$.

First results from the BEST Collaboration searching for short-baseline neutrino oscillations to sterile neutrinos with a high-intensity ${}^{51}$Cr monoenergetic neutrino source reaffirm that the so-called gallium anomaly, a deficit in electron neutrinos, persists. $4\ensuremath{\sigma}$ deficits were observed in the ${}^{71}$Ge production rates at two different distance scales, which could be interpreted as oscillations between an electron neutrino and a hypothetical sterile neutrino. The results are consistent with oscillations with a mass squared difference above about 0.5 eV${}^{2}$ and a large mixing angle ${\mathrm{sin}}^{2}\phantom{\rule{0.167em}{0ex}}2\ensuremath{\theta}\ensuremath{\approx}0.4$.

The author presents compelling arguments that measurements of collective flow in high-energy nuclear collisions can provide information on the shape of atomic nuclei on time scales several orders of magnitude shorter than are probed in low-energy experiments.

This work studies the production of direct photons in relativistic nuclear collisions, along with the production of hadrons. Radiation from the very first instants to the final moments of the evolution is included. The hybrid model used here describes all stages of relativistic heavy-ion collisions. Chronologically, those are an initial state reflecting the collision of nuclei described within the color glass condensate effective theory; a pre-equilibrium phase based on nonequilibrium linear response; relativistic viscous hydrodynamics, and a hadronic afterburner. The effect of the pre-equilibrium phase on both photonic and hadronic observables is highlighted for the first time. The potential of photon observables---spectrum, differential elliptic, and triangular flow---to reveal the chemical equilibration time is studied. Finally, we consider ``small collision systems,'' including $\text{proton}+\text{nucleus}$ collisions and collisions of light nuclei, as probed by hadronic and electromagnetic observables. We demonstrate how photon production can signal the formation of…

The structure of atomic nuclei is shown to influence a collection of observables measured in relativistic heavy-ion collisions. Details of the nuclear shape---here its triaxial nature---and of its fluctuations are reflected in the angular correlations between the detected particles, establishing a connection between high-energy nuclear collisions and low-energy nuclear structure.

Charge radius is one of the most fundamental properties of a nucleus. However, a precise description of the evolution of charge radii along an isotopic chain is highly nontrivial, as reinforced by recent experimental measurements. In this paper, we propose a novel approach which combines a three-parameter formula and a Bayesian neural network. We find that the novel approach can describe the charge radii of all $A\ensuremath{\ge}40$ and $Z\ensuremath{\ge}20$ nuclei with a root-mean-square deviation about 0.015 fm. In particular, the charge radii of the calcium isotopic chain are reproduced very well, including the parabolic behavior and strong odd-even staggerings. We further test the approach for the potassium isotopes and show that it can describe well the experimental data within uncertainties.

Single- reference coupled-cluster theory is an accurate and affordable computational method for the nuclear many-body problem. For open-shell nuclei, the reference state typically breaks rotational invariance and angular momentum must be restored as a good quantum number. We perform angular-momentum projection after variation and employ the disentangled coupled-cluster formalism and a Hermitian approach. We compare our results with benchmarks for $^{8}\mathrm{Be}$ and $^{20}\mathrm{Ne}$ using a two-nucleon interaction from chiral effective field theory and for $pf$-shell nuclei within the traditional shell model. We compute the rotational band in the exotic nucleus $^{34}\mathrm{Mg}$ and find agreement with data.

To study the bulk properties of quark-gluon plasma produced at beam-energy scan (BES) energies at the Relativistic Heavy Ion Collider (RHIC), we extend the $(3+1)$-dimensional viscous hydrodynamics clvisc to include net baryon number conservation and Israel-Stewart--like equations for baryon diffusion with the neos-bqs equation of state, fluctuating initial conditions from the Monte Carlo Glauber model and the afterburner smash. This integrated framework is shown to provide a good description of identified particle spectra, mean transverse momenta, and anisotropic flows for different centralities and over a wide range of collision energies (7.7--62.4 GeV). It is found that the mean momenta of identified particles and anisotropic flows increase mildly with the collision energy due to larger radial flow. We further compute the multiple-particle cumulant ratio ${v}_{2}{4}/{v}_{2}{2}$ of elliptic flow across BES energies, and find that the relative fluctuations of elliptic flow are insensitive to the collision energy, consistent with the preliminary STAR data. Our model provides a…

Here, we present results of the first experiment aimed at the synthesis of Mc isotopes in the 243Am+48Ca reaction performed at the new gas-filled separator DGFRS-2 online to the new cyclotron DC280 at the Super Heavy Element Factory at JINR. Fifty-five new decay chains of 288Mc and six chains assigned to 289Mc were detected. The α decay of 268Db with an energy of 7.6–8.0 MeV, half-life of 16$^{+6}_{-4}$h, and a branch of 55$^{+20}_{-15}$% was registered for the first time, and a new spontaneously fissioning isotope 264Lr with a half-life of 4.9$^{+2.1}_{-1.3}$h was identified. The cross section for the 243Am(48Ca,3n)288Mc reaction was measured to be 17.1$^{+6.3}_{-4.7}$ pb, which is the largest value for the known superheavy nuclei at the island of stability.

The variational quantum eigensolver (VQE) is an algorithm to compute ground and excited state energy of quantum many-body systems. A key component of the algorithm and an active research area is the construction of a parametrized trial wave function---a so-called variational ansatz. The wave function parametrization should be expressive enough, i.e., represent the true eigenstate of a quantum system for some choice of parameter values. On the other hand, it should be trainable, i.e., the number of parameters should not grow exponentially with the size of the system. Here, we apply VQE to the problem of finding ground and excited state energies of the odd-odd nucleus $^{6}\mathrm{Li}$. We study the effects of ordering fermionic excitation operators in the unitary coupled clusters ansatz on the VQE algorithm convergence by using only operators preserving the ${J}_{z}$ quantum number. The accuracy is improved by two orders of magnitude in the case of descending order. We first compute optimal ansatz parameter values using a classical state-vector simulator with arbitrary measurement…

Employing the $^{11}\mathrm{B}(p,\ensuremath{\gamma})^{12}\mathrm{C}$ nuclear reaction, the angular correlation of ${e}^{+}{e}^{\ensuremath{-}}$ pairs was investigated in the angular range of ${40}^{\ensuremath{\circ}}\ensuremath{\le}\mathrm{\ensuremath{\Theta}}\ensuremath{\le}{175}^{\ensuremath{\circ}}$ for five different proton energies between ${E}_{p}=1.50$--2.5 MeV. At small angles ($\mathrm{\ensuremath{\Theta}}\ensuremath{\le}{120}^{\ensuremath{\circ}}$), the results can be well interpreted by the internal pair creation process of electromagnetic radiations with $E1$ and $M1$ multipolarities and by the external pair creation in the target backing. However, at angles greater than ${120}^{\ensuremath{\circ}}$, additional count excesses and anomalies were observed, which could be well accounted for by the existence of the previously suggested hypothetical X17 particle. Our results suggest that the X17 particle was generated mainly in $E1$ radiation. The derived mass of the particle is…

We present a systematic study of $f$-mode oscillations in neutron stars containing hyperons, extending recent results obtained within the Cowling approximation to linearized general relativity. Employing a relativistic mean-field model, we find that the Cowling approximation can overestimate the quadrupolar $f$-mode frequency of neutron stars by up to 30% compared to the frequency obtained in the linearized general relativistic formalism. Imposing current astrophysical constraints, we derive updated empirical relations for gravitational wave asteroseismology. The frequency and damping time of quadrupole $f$-mode oscillations of hyperonic stars are found to be in the range of 1.47--2.45 kHz and 0.13--0.51 s, respectively. Our correlation studies demonstrate that among the various parameters of the nucleonic and hyperonic sectors of the model, the nucleon effective mass shows the strongest correlation with mode characteristics and neutron star observables. Estimates for the detectability of $f$ modes in a transient burst of gravitational waves from isolated hyperonic stars is also…

Background: One fascinating frontier in nuclear physics is the study of exotic nuclei. The deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc), which simultaneously includes the nuclear superfluidity, deformation, and continuum effects, can provide proper descriptions for both stable and exotic nuclei. In a previous work [Zhang et al., Phys. Rev. C 102, 024314 (2020)], the DRHBc theory based on the point-coupling density functionals was developed and the DRHBc calculation, previously accessible only for light nuclei, was extended for all even-even nuclei in the nuclear chart. The ground-state properties for the even-even nuclei with $8\ensuremath{\le}Z\ensuremath{\le}120$ from the DRHBc calculations have been summarized [Zhang et al., At. Data Nucl. Data Tables 144, 101488 (2022)].Purpose: The aim of this paper is to extend the point-coupling DRHBc theory to odd-$A$ and odd-odd nuclei and examine its applicability by taking odd-$A$ Nd isotopes as examples.Method: In the DRHBc theory, the densities and potentials with axial deformation are expanded in terms of…

Modeling of nuclear masses is important for many areas of nuclear science including nuclear astrophysics, reaction modeling, and nuclear data evaluations, but accuracy is challenging. This paper shows how judicious use of physics knowledge---so-called feature-space engineering---in machine learning, coupled with sophisticated models of theoretical uncertainties, can lead to better predictions.

This work presents a three-dimensional dynamical initialization model for relativistic heavy-ion collisions, implementing local energy-momentum conservation and baryon charge fluctuations at string junctions. Constraining parameters using experimental data from $p+p$ collisions at various collision energies, the model provides a very good description of the charged hadron and net proton rapidity distributions in $\mathrm{Au}+\mathrm{Au}$ collisions from 7.7 to 200 GeV and $\mathrm{Pb}+\mathrm{Pb}$ collisions at 8.77 and 17.3 GeV. We demonstrate the importance of fluctuations of baryon densities to string junctions for describing net-proton distributions at collision energies of 62.4 and 200 GeV. Including this improved baryon stopping description along with the requirement of strangeness neutrality also yields a good description of identified particle yields as functions of the collision energy above 7.7 GeV. We further study asymmetric $p+\mathrm{Al}$ and $(p,d,^{3}\mathrm{He})+\mathrm{Au}$ collisions at the top Relativistic Heavy-Ion Collider (RHIC) energy and $p+\mathrm{Pb},…

We present an approach to modeling the ground-state mass of atomic nuclei based directly on a probabilistic neural network constrained by relevant physics. Our physically interpretable machine learning (PIML) approach incorporates knowledge of physics by using a physically motivated feature space in addition to a soft physics constraint that is implemented as a penalty to the loss function. We train our PIML model on a random set of approximately 20% of the atomic mass evaluation (AME) and predict the remaining 80%. The success of our methodology is exhibited by a ${\ensuremath{\sigma}}_{\mathrm{rms}}\ensuremath{\approx}186$ keV match to data for the training set and ${\ensuremath{\sigma}}_{\mathrm{rms}}\ensuremath{\approx}316$ keV for the entire AME with $Z\ensuremath{\ge}20$. We show that our general methodology can be interpreted using feature importance.

We use the Lipkin-Meshkov-Glick (LMG) model and the valence-space nuclear shell model to examine the likely performance of variational quantum eigensolvers in nuclear-structure theory. The LMG model exhibits both a phase transition and spontaneous symmetry breaking at the mean-field level in one of the phases, features that characterize collective dynamics in medium-mass and heavy nuclei. We show that with appropriate modifications, the ADAPT-VQE algorithm, a particularly flexible and accurate variational approach, is not troubled by these complications. We treat up to 12 particles and show that the number of quantum operations needed to approach the ground-state energy scales linearly with the number of qubits. We find similar scaling when the algorithm is applied to the nuclear shell model with realistic interactions in the $sd$ and $pf$ shells. Although most of these simulations contain no noise, we use a noise model from real IBM hardware to show that for the LMG model with four particles, weak noise has no effect on the efficiency of the algorithm.

We explore the preparation of specific nuclear states on gate-based quantum hardware using variational algorithms. Large-scale classical diagonalizations of the nuclear shell model have reached sizes of ${10}^{9}--{10}^{10}$ basis states but are still severely limited by computational resources. Quantum computing can, in principle, solve such systems exactly with exponentially fewer resources than classical computing. Exact solutions for large systems require many qubits and large gate depth, but variational approaches can effectively limit the required gate depth. We use the unitary coupled cluster approach to construct approximations of the ground-state vectors, later to be used in dynamics calculations. The testing ground is the phenomenological shell model space, which allows us to mimic the complexity of the internucleon interactions. We find that often one needs to minimize over a large number of parameters, using a large number of entanglements that makes the application on existing hardware challenging. Prospects for rapid improvements with more capable hardware are,…

We present a dynamical description of (anti)proton number cumulants and correlation functions in central Au-Au collisions at $\sqrt{{s}_{NN}}=7.7--200\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$ by utilizing viscous hydrodynamics simulations. The cumulants of proton and baryon number are calculated in a given momentum acceptance analytically, via an appropriately extended Cooper-Frye procedure describing particlization of an interacting hadron resonance gas. The effects of global baryon number conservation are taken into account using a generalized subensemble acceptance method. The experimental data of the STAR Collaboration are consistent at $\sqrt{{s}_{NN}}\ensuremath{\gtrsim}20\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$ with simultaneous effects of global baryon number conservation and repulsive interactions in the baryon sector, the latter being in line with the behavior of baryon number susceptibilities observed in lattice QCD. The data at lower collision energies show possible indications for sizable attractive interactions among baryons. The data also indicate sizable negative…

We present a systematic study of $\mathrm{\ensuremath{\Lambda}}$ hyperon's polarization observables using event-by-event ($3+1$) dimensional relativistic hydrodynamics. The effects of initial hot spot size and quark gluon plasma's specific shear viscosity on the polarization observables are quantified. We examine the effects of the two formulations of the thermal shear tensor on the polarization observables using the same hydrodynamic background. With event-by-event simulations, we make predictions for the Fourier coefficients of ${\mathrm{\ensuremath{\Lambda}}}^{\ensuremath{'}}\mathrm{s}$ longitudinal polarization ${P}^{z}$ with respect to the event planes of different orders of anisotropic flow. We propose new correlations among the Fourier coefficients of ${P}^{z}$ and charged hadron anisotropic flow coefficients to further test the mapping from fluid velocity gradients to hyperon's polarization. Finally, we present a system size scan with $\mathrm{Au}+\mathrm{Au}$, $\mathrm{Ru}+\mathrm{Ru}$, and $\mathrm{O}+\mathrm{O}$ collisions at…

We study a family of equations of state (EOS) for hybrid neutron star matter. The hybrid EOS are obtained by a Maxwell construction of the first-order phase transition between a hadronic phase described by the relativistic density-functional EOS of the ``DD2'' class with excluded volume effects and a deconfined quark matter phase modeled by an instantaneous nonlocal version of the Nambu--Jona-Lasinio model in $\text{SU}{(2)}_{f}$ with vector interactions and color superconductivity. The form factor in the nonlocal quark matter model is fitted to lattice QCD results in the Coulomb gauge. Owing to strong coupling in the vector meson and diquark channels, a coexistence phase of color superconductivity and chiral symmetry breaking occurs. Our results show an approximately constant behavior for the squared speed of sound with values of 0.4--0.6 in the density region relevant for neutron star interiors. To simultaneously fulfill the constraints from the Neutron Star Interior Composition Explorer radius measurement for PSR $\mathrm{J}0740+6620$ and tidal deformability from GW170817 it is…

The electromagnetic response of hot QCD matter to decaying external magnetic fields is investigated.We examine the validity of Ohm's law and find that the induced electric current increases from zero and relaxes towards the value from Ohm's law.The relaxation time is larger than the lifetime of the external magnetic field for the QCD matter in relativistic heavy-ion collisions.The lower-than-expected electric current significantly suppresses the induced magnetic field and makes the electromagnetic response incomplete.We demonstrate the incomplete electromagnetic response of hot QCD matter by calculations employing the parton transport model combined with the solution of Maxwell's equations.Our results show a strong suppression by two orders of magnitude in the magnetic field relative to calculations assuming the validity of Ohm's law.This may undermine experimental efforts to measure magnetic-field-related effects in heavy-ion collisions.

In this paper, we present results of the second experiment on the synthesis of Mc isotopes in the $^{243}\mathrm{Am}+^{48}\mathrm{Ca}$ reaction performed at the gas-filled separator DGFRS-2 of the SHE Factory at JINR. The new isotope $^{286}\mathrm{Mc}$ was synthesized, and its half-life of $20\begin{array}{c}+98\\ \ensuremath{-}9\end{array}$ ms and \ensuremath{\alpha}-particle energy of $10.71\ifmmode\pm\else\textpm\fi{}0.02$ MeV were determined. A $^{286}\mathrm{Mc} \ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{decay}$ chain was recorded down to the spontaneous fission of $^{266}\mathrm{Db}$. The spontaneous fission of $^{279}\mathrm{Rg}$ was observed for the first time in one of four new decay chains of $^{287}\mathrm{Mc}$. The excitation function of the reaction was measured at three $^{48}\mathrm{Ca}$ energies of 242, 250, and 259 MeV; the latter resulted in the first observation of the $5n\text{\ensuremath{-}}\mathrm{evaporation}$ channel with a cross section of $0.{5}_{\ensuremath{-}0.4}^{+1.3}$ pb. The decay properties of 21 previously known…

We perform a systematic study on the local and global spin polarization of $\mathrm{\ensuremath{\Lambda}}$ and $\overline{\mathrm{\ensuremath{\Lambda}}}$ hyperons in relativistic heavy-ion collisions at beam energy scan energies via the ($3+1$)-dimensional CLVisc hydrodynamics model with a multiphase transport (AMPT) and simulating many accelerated strongly interacting hadron (SMASH) initial conditions. Following the quantum kinetic theory, we decompose the polarization vector as the parts induced by thermal vorticity, shear tensor and the spin Hall effect (SHE). We find that the polarization induced by the SHE and the total polarization strongly depends on the initial conditions. At $7.7\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$, the SHE gives a sizable contribution and even flips the sign of the local polarization along the beam direction for the AMPT initial condition, which is not observed for the SMASH initial condition. Meanwhile, the local polarization along the out-of-plane direction induced by the SHE with the AMPT initial condition does not always increase with decreasing…

Machine learning is employed to build an energy density functional for self-bound nuclear systems for the first time. By learning the kinetic energy as a functional of the nucleon density alone, a robust and accurate orbital-free density functional for nuclei is established. Self-consistent calculations that bypass the Kohn-Sham equations provide the ground-state densities, total energies, and root-mean-square radii with a high accuracy in comparison with the Kohn-Sham solutions. No existing orbital-free density functional theory comes close to this performance for nuclei. Therefore, it provides a new promising way for future developments of nuclear energy density functionals for the whole nuclear chart.

The momentum correlation functions of $S=\ensuremath{-}2$ baryon pairs ($p{\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}}$ and $\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}$) produced in high-energy $pp$ and $pA$ collisions are investigated on the basis of the coupled-channels formalism. The strong interaction is described by the coupled-channels HAL QCD potential obtained by lattice QCD simulations near physical quark masses, while the hadronic source function is taken to be a static Gaussian form. The coupled-channels effect, the threshold difference, the realistic strong interaction, and the Coulomb interaction are fully taken into account for the first time in the femtoscopic analysis of baryon-baryon correlations. The characteristic features of the experimental data for the $p{\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}}$ and $\mathrm{\ensuremath{\Lambda}}\mathrm{\ensuremath{\Lambda}}$ pairs at the Large Hadron Collider are reproduced quantitatively with a suitable choice of nonfemtoscopic parameters and the source size. The agreement between theory and experiment…

Experiments using a $^{48}\mathrm{Ca}$ beam on $^{238}\mathrm{U}$ and $^{242}\mathrm{Pu}$ targets to produce superheavy nuclei were performed at the gas-filled separator DGFRS-2 online to the new cyclotron DC280 at the SHE Factory at JINR. The decay properties of $^{286}\mathrm{Fl}$ and $^{287}\mathrm{Fl}$, as well as their \ensuremath{\alpha}-decay products, were refined after the detection of 25 and 69 new decay chains, respectively. In addition, 16 decay chains of $^{283}\mathrm{Cn}$ were observed in the $^{238}\mathrm{U}+^{48}\mathrm{Ca}$ reaction. The possibility of existing of isomeric states in the $^{287}\mathrm{Fl}$ consecutive \ensuremath{\alpha} decays is discussed. A new \ensuremath{\alpha} line with an energy of 100--200 keV lower than the main one at 10.19 MeV was observed for the first time for even-even $^{286}\mathrm{Fl}$ decay. A maximum cross section of $10.{4}_{\ensuremath{-}2.1}^{+3.5}\mathrm{pb}$ was measured for the $^{242}\mathrm{Pu}(^{48}\mathrm{Ca},3n) ^{287}\mathrm{Fl}$ reaction.

Background: Recent developments in ab initio nuclear theory demonstrate promising results in medium- to heavy-mass nuclei. A particular challenge for many of the many-body methodologies, however, is an accurate treatment of the electric-quadrupole, $E2$, strength associated with collectivity.Purpose: The valence-space in-medium similarity renormalization group (VS-IMSRG) is a particularly powerful method for accessing medium- and high-mass nuclei but has been found to underpredict $E2$ strengths. The purpose of this work is to evaluate the isospin dependence of this underprediction.Methods: We perform a systematic comparison of VS-IMSRG calculations with available literature. We make use of isoscalar and isovector contributions to the $E2$ matrix elements to assess isoscalar and isovector contributions to the missing strength.Results: It is found that the $E2$ strength is consistent throughout ${T}_{z}=|\frac{1}{2}|, {T}_{z}=|1|, {T}_{z}=|\frac{3}{2}|$, and ${T}_{z}=2$ pairs within the $sd$ shell. Furthermore, no isovector contribution to the deficiency is identified.Conclusions: A…

We describe and implement a procedure for determining the couplings of a relativistic mean-field theory (RMFT) that is optimized for application to neutron star phenomenology. In the standard RMFT approach, the couplings are constrained by comparing the theory's predictions for symmetric matter at saturation density with measured nuclear properties. The theory is then applied to neutron stars which consist of neutron-rich matter at densities ranging up to several times saturation density, which allows for additional astrophysical constraints. In our approach, rather than using the RMFT to extrapolate from symmetric to neutron-rich matter and from finite-sized nuclei to uniform matter, we fit the RMFT to properties of uniform pure neutron matter obtained from chiral effective field theory. Chiral effective field theory incorporates the experimental data for nuclei in the framework of a controlled expansion for nuclear forces valid at nuclear densities and enables us to account for theoretical uncertainties when fitting the RMFT. We construct four simple RMFTs that span the…

The beam energy dependence of the directed flow is a sensitive probe for the properties of strongly interacting matter. Hybrid models that simulate dense (core) and dilute (corona) parts of the system by combining the fluid dynamics and hadronic cascade model describe well the bulk observables, strangeness productions, and radial and elliptic flows in high-energy heavy-ion collisions in the high baryon density region. However, the beam energy dependence of the directed flow cannot be described in existing hybrid models. We focus on improving the corona part, i.e., the nonequilibrium evolution part of the system, by introducing the mean-field potentials into a hadronic cascade model. For this purpose, we consider different implementations of momentum-dependent hadronic mean fields in the relativistic quantum molecular dynamics (RQMD) framework. First, Lorentz scalar implementation of a Skyrme type potential is examined. Then, full implementation of the Skyrme type potential as a Lorentz vector in the RQMD approach is proposed. We find that scalar implementation of the Skyrme force is…

We present the reduced basis method as a tool for developing emulators for equations with tunable parameters within the context of the nuclear many-body problem. The method uses a basis expansion informed by a set of solutions for a few values of the model parameters and then projects the equations over a well-chosen low-dimensional subspace. We connect some of the results in the eigenvector continuation literature to the formalism of reduced basis methods and show how these methods can be applied to a broad set of problems. As we illustrate, the possible success of the formalism on such problems can be diagnosed beforehand by a principal component analysis. We apply the reduced basis method to the one-dimensional Gross-Pitaevskii equation with a harmonic trapping potential and to nuclear density functional theory for $^{48}\mathrm{Ca}$, achieving speed-ups of more than $\ifmmode\times\else\texttimes\fi{}150$ and $\ifmmode\times\else\texttimes\fi{}250$, respectively, when compared to traditional solvers. The outstanding performance of the approach, together with its straightforward…

We calculate the transverse momentum broadening $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{q}$ and collisional energy loss $dE/dx$ of hard probes traversing an evolving glasma during the earliest phase of a relativistic heavy-ion collision. We use a Fokker-Planck equation and apply a proper time expansion to describe the temporal evolution of the glasma. The correlators of the chromodynamic fields that determine the Fokker-Planck collision terms, which in turn provide $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{q}$ and $dE/dx$, are computed to fifth order. Both transport coefficients are strongly dependent on time. The maximum values they acquire before the proper time expansion breaks down are large: $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{q}$ is of the order of a few ${\mathrm{GeV}}^{2}/\mathrm{fm}$ and $dE/dx\ensuremath{\sim}1\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}/\mathrm{fm}$. Their precise values depend on the probe's velocity $\mathbf{v}$, the saturation momentum ${Q}_{s}$, and an IR regulator $m$ that is related to the confinement scale. We study the dependence of our…

We study cluster and hypernuclei production in heavy-ion collisions at relativistic energies employing the parton-hadron-quantum-molecular-dynamics (PHQMD) approach, a microscopic $n$-body transport model based on the QMD propagation of the baryonic degrees of freedom with density dependent two-body potential interactions. All other ingredients of PHQMD, including the collision integral and the treatment of the quark-gluon plasma (QGP) phase, are adopted from the parton-hadron-string-dynamics (PHSD) approach. In PHQMD the cluster formation occurs dynamically, caused by the interactions. The clusters are recognized by the Minimum Spanning Tree (MST) algorithm. We present the PHQMD results for cluster and hypernuclei formation in comparison with the available experimental data at energies available at the Alternating Gradient Synchrotron, the Super Proton Synchrotron, and the Beam Energy Scan and fixed-target programs at the BNL Relativistic Heavy Ion Collider. We also provide predictions on cluster production for the upcoming experiments at the GSI Facility for Antiproton and Ion…

We present the first next-to-leading-order (NLO) perturbative QCD (pQCD) study of rapidity-differential cross sections of coherent exclusive photoproduction of $J/\ensuremath{\psi}$ mesons in heavy-ion ultraperipheral collisions (UPCs) at the CERN Large Hadron Collider (LHC), $d\ensuremath{\sigma}/dy(\text{Pb}+\text{Pb}\ensuremath{\rightarrow}\text{Pb}+J/\ensuremath{\psi}+\text{Pb})$. For this, we account for the photon-nucleon NLO cross sections at the forward limit, the $t$ dependence using a standard nuclear form factor, and the photon fluxes of the colliding nuclei. Approximating the generalized parton distributions with their forward-limit parton distribution functions (PDFs), we quantify the NLO contributions in the cross sections, show that the real part of the amplitude and quark-PDF contributions must not be neglected, quantify the uncertainties arising from the scale choice and PDFs, and compare our results with ALICE, CMS, and LHCb $J/\ensuremath{\psi}$ photoproduction data in $\mathrm{Pb}+\mathrm{Pb}$ UPCs, exclusive $J/\ensuremath{\psi}$ photoproduction data from HERA,…

Causality is violated in the early stages of state-of-the-art heavy-ion hydrodynamic simulations. Such violations are present in up to 75% of the fluid cells in the initial time and only after 2--3 fm/$c$ of evolution do we find that $50%$ of the fluid cells are definitely causal. Superluminal propagation reaches up to 15% the speed of light in some of the fluid cells. The inclusion of pre-equilibrium evolution significantly reduces the number of acausal cells. Our findings suggests that relativistic causality may place constraints on the available parameter space of heavy-ion collision simulations when factored into more thorough statistical analyses.

We introduce a global analysis of relativistic heavy ion collisions using Trajectum of a significantly higher precision and including a new option to vary the normalization of the centrality estimator. We use the posterior distribution of our parameters to generate a set of high-statistics samples that allows us to make precise predictions including statistical and systematic uncertainties estimated from the model parameter distribution. The results are systematically compared with experiment whereby we also include many observables not included in the global analysis. This includes in particular (extremely) ultracentral anisotropic flow and mean transverse momentum, whereby we find satisfactory agreement with experiment where data are available. Lastly, we compute spectra and anisotropic flow for oxygen-oxygen collisions performed at the BNL Relativistic Heavy Ion Collider (RHIC) and to be performed at the the CERN Large Hadron Collider (LHC) and comment on how these collisions may inform us on properties of the quark-gluon plasma.

Ab initio calculations of nuclear masses, binding energy, and $\ensuremath{\alpha}$-decay half-lives are intractable for heavy nucleus because of the curse of dimensionality in many-body quantum simulations as proton number ($N$) and neutron number ($Z$) grow. We take advantage of the powerful nonlinear transformation and feature representation ability of deep neural network (DNN) to predict the nuclear masses and $\ensuremath{\alpha}$-decay half-lives. For nuclear binding energy prediction problem we achieve standard deviation $\ensuremath{\sigma}=0.263$ MeV on 10-fold cross validation on 2149 nuclei. Word-vectors which are high-dimensional representation of nuclei from the hidden layers of mass-regression DNN help us to calculate $\ensuremath{\alpha}$-decay half-lives. For this task, we get $\ensuremath{\sigma}=0.797$ on 100 times 10-fold cross validation on 350 nuclei on ${\text{log}}_{10}{T}_{1/2}$ and $\ensuremath{\sigma}=0.731$ on 486 nuclei. DNN is also used to reduce the residual of three-parameter Gamow formula on 159 even-even nuclei, from 0.3627 to 0.2297 on…

We present developments and applications for the diagonalization of shell-model Hamiltonians in a discrete nonorthogonal basis. The method, and its actual numerical implementation carina, based on mean-field and beyond-mean-field techniques, has already been applied in previous studies and is focused on basis states selection optimization. The method is benchmarked against a full set of $sd$ shell exact diagonalizations, and is applied for the first time to the heavy deformed $^{254}\mathrm{No}$ nucleus.

We present a comprehensive investigation of few-nucleon systems as well as light and medium-mass nuclei up to $A=48$ using the current Low Energy Nuclear Physics International Collaboration two-nucleon interactions in combination with the third-order (${\mathrm{N}}^{2}\mathrm{LO}$) three-nucleon forces. To address the systematic overbinding of nuclei starting from $A\ensuremath{\approx}10$ found in our earlier study utilizing the ${\mathrm{N}}^{2}\mathrm{LO}$ two- and three-nucleon forces, we take into account higher-order corrections to the two-nucleon potentials up through fifth order in chiral effective field theory. The resulting Hamiltonian can be completely determined using the $A=3$ binding energies and selected nucleon-deuteron cross sections as input. It is then shown to predict other nucleon-deuteron scattering observables and spectra of light $p$-shell nuclei, for which a detailed correlated truncation error analysis is performed, in agreement with experimental data. Moreover, the predicted ground state energies of nuclei in the oxygen isotopic chain from…

In heavy ion collisions, elliptic flow ${v}_{2}$ and radial flow, characterized by eventwise average transverse momentum $[{p}_{\mathrm{T}}]$, are related to the shape and size of the overlap region, which are sensitive to the shape of colliding atomic nuclei. The Pearson correlation coefficient between ${v}_{2}$ and $[{p}_{\mathrm{T}}], {\ensuremath{\rho}}_{2}$, was found to be particularly sensitive to the quadrupole deformation parameter $\ensuremath{\beta}$ that is traditionally measured in low energy experiments. Built on earlier insight that the prolate deformation $\ensuremath{\beta}>0$ reduces the ${\ensuremath{\rho}}_{2}$ in ultracentral collisions (UCC), we show that the prolate deformation $\ensuremath{\beta}<0$ enhances the value of ${\ensuremath{\rho}}_{2}$. As $\ensuremath{\beta}>0$ and $\ensuremath{\beta}<0$ are the two extremes of triaxiality, the strength and sign of ${v}_{2}^{2}\text{\ensuremath{-}}[{p}_{\mathrm{T}}]$ correlation can be used to provide valuable information on the triaxiality of the nucleus. Our study provide further arguments for using the…

For the first time, the calculation of the nuclear matrix element of the double-$\ensuremath{\beta}$ decay of $^{100}\mathrm{Mo}$, with and without the emission of two neutrinos, is performed in the framework of the nuclear shell model. This task is accomplished starting from a realistic nucleon-nucleon potential, then the effective shell-model Hamiltonian and decay operators are derived within the many-body perturbation theory. The exotic features which characterize the structure of Mo isotopes---such as shape coexistence and triaxiality softness---push the shell-model computational problem beyond its present limits, making it necessary to truncate the model space. This has been done with the goal to preserve as much as possible the role of the rejected degrees of freedom in an effective approach that has been introduced and tested in previous studies. This procedure is grounded on the analysis of the effective single-particle energies of a large-scale shell-model Hamiltonian, that leads to a truncation of the number of the orbitals belonging to the model space. Then, the original…

The production of ${K}^{*}{(892)}^{0}$ and $\ensuremath{\phi}(1020)$ mesons in proton--proton $(pp)$ and lead--lead (Pb--Pb) collisions at $\sqrt{{s}_{NN}}$ $=$ 5.02 TeV has been measured using the ALICE detector at the Large Hadron Collider (LHC). The transverse momentum $({p}_{\mathrm{T}})$ distributions of ${K}^{*}{(892)}^{0}$ and $\ensuremath{\phi}(1020)$ mesons have been measured at midrapidity $(|y|<0.5)$ up to ${p}_{\mathrm{T}}\phantom{\rule{4pt}{0ex}}=$ 20 $\mathrm{GeV}/c$ in inelastic $pp$ collisions and for several Pb--Pb collision centralities. The collision centrality and collision energy dependence of the average transverse momenta agree with the radial flow scenario observed with stable hadrons, showing that the effect is stronger for more central collisions and higher collision energies. The ${K}^{*0}/K$ ratio is found to be suppressed in Pb--Pb collisions relative to $pp$ collisions: this indicates a loss of the measured ${K}^{*}{(892)}^{0}$ signal due to rescattering of its decay products in the hadronic phase. In contrast, for the longer-lived…

We explore the possibility to perform symmetry restoration with the variation after projection technique on a quantum computer followed by additional postprocessing. The final goal is to develop configuration interaction techniques based on many-body trial states preoptimized on a quantum computer. We show how the projection method used for symmetry restoration can prepare optimized states that could then be employed as initial states for quantum or hybrid quantum-classical algorithms. We use the quantum phase estimation and the quantum Krylov approaches for the postprocessing. The latter method combined with the quantum variation after projection leads to very fast convergence toward the ground-state energy. The possibility to access excited states energies is also discussed. Illustrations of the different techniques are made using the pairing Hamiltonian.

The combined dinuclear system (DNS) model and statistical model incorporated in kewpie2 have been used to study the prospects for the synthesis of a superheavy element (SHE) with $Z=119$ in the $^{54}\mathrm{Cr}+^{243}\mathrm{Am}$ fusion reaction. The method of calculation has been verified by description of the evaporation residue cross sections measured for the $^{48}\mathrm{Ca}+^{243}\mathrm{Am}$ reaction. The calculated results of the partial and total cross sections for the complete fusion, quasifission, fast fission, and evaporation residues formation for both reactions are discussed.

This work uses two liquid-xenon detectors in the Gran Sasso Underground Laboratory, originally designed to search for dark matter, to find evidence for neutrinoless double-$\ensuremath{\beta}$ decay. The results indicate that such dark-matter detectors can provide important constraints and potential discoveries beyond their original purpose and design. This is further illustrated by the first statistically significant observation of a rare two-neutrino decay of ${}^{124}$Xe.

The mean spin polarization vector of spin 1/2 particles in a relativistic fluid at local thermal equilibrium (LTE) in different pseudogauges (PGs), i.e., with different choices for the decomposition of orbital and spin angular momentum, is obtained. The spin polarization obtained in the canonical PG differs from the one obtained in the Belinfante PG. It is found that this difference can not be written by replacing the thermal vorticity with the spin potential in the usual polarization formula. Other PG choices affect the contribution of thermal shear to the spin polarization. Therefore, the choice of a PG affects the predictions for the polarization measured in heavy-ion collisions. In general, it is shown that the Wigner function of a noninteracting Dirac field at LTE is affected by the PG transformations. Explicit expressions of the mean axial current are also calculated and it is found that even the axial vortical effect conductivity depends on the PG.

The dynamics of low-energy-induced fission is explored using a consistent microscopic framework that combines the time-dependent generator coordinate method (TDGCM) and time-dependent nuclear density functional theory (TDDFT). While the former presents a fully quantum mechanical approach that describes the entire fission process as an adiabatic evolution of collective degrees of freedom, the latter models the dissipative dynamics of the final stage of fission by propagating the nucleons independently toward scission and beyond. The two methods, based on the same nuclear energy density functional and pairing interaction, are employed in an illustrative study of the charge distribution of yields and total kinetic energy for induced fission of $^{240}\mathrm{Pu}$. For the saddle-to-scission phase a set of initial points for the TDDFT evolution is selected along an isoenergy curve beyond the outer fission barrier on the deformation energy surface, and the TDGCM is used to calculate the probability that the collective wave function reaches these points at different times. Fission…

Using and comparing kinetic theory and second-order Chapman-Enskog hydrodynamics, we study the nonconformal dynamics of a system undergoing Bjorken expansion. We use the concept of ``free-streaming fixed lines'' for scaled shear and bulk stresses in nonconformal kinetic theory and hydrodynamics, and show that these fixed lines behave as early-time attractors and repellors of the evolution. In the conformal limit, the free-streaming fixed lines reduce to the well-known fixed points of conformal Bjorken dynamics. A new fixed point in the free streaming regime is identified which lies at the intersection of these fixed lines. Contrary to the conformal scenario, both kinetic theory and hydrodynamics predict the absence of attractor behavior in the normalized shear stress channel. In kinetic theory a far-off-equilibrium attractor is found for the normalized effective longitudinal pressure, driven by rapid longitudinal expansion. Second-order viscous hydrodynamics fails to accurately describe this attractor. From a thorough analysis of the free-streaming dynamics in Chapman-Enskog…