The 50 most-cited articles in Physical Review C, 2017

The beam-energy scan at RHIC aims to discover whether a critical point exists in the phase diagram of QCD. This paper reports on the most comprehensive measurement of single-particle spectra for a multitude of hadrons from the first run, taken with the STAR experiment. From these the authors infer the kinetic and chemical freeze-out temperatures and the baryon chemical potential as functions of beam energy and centrality. The results provide an opportunity for the beam-energy scan program at RHIC to enlarge the ($T,\ensuremath{\mu}\phantom{\rule{0}{0ex}}B$) region of the phase diagram to search for the QCD critical point.

We present $\mathit{NN}$ potentials through five orders of chiral effective field theory ranging from leading order (LO) to next-to-next-to-next-to-next-to-leading order (${\mathrm{N}}^{4}\mathrm{LO}$). The construction may be perceived as consistent in the sense that the same power counting scheme as well as the same cutoff procedures are applied in all orders. Moreover, the long-range parts of these potentials are fixed by the very accurate $\ensuremath{\pi}N$ low-energy constants (LECs) as determined in the Roy-Steiner equations analysis by Hoferichter, Ruiz de Elvira, and coworkers. In fact, the uncertainties of these LECs are so small that a variation within the errors leads to effects that are essentially negligible, reducing the error budget of predictions considerably. The $\mathit{NN}$ potentials are fit to the world $\mathit{NN}$ data below the pion-production threshold of the year 2016. The potential of the highest order (${\mathrm{N}}^{4}\mathrm{LO}$) reproduces the world $\mathit{NN}$ data with the outstanding ${\ensuremath{\chi}}^{2}$/datum of 1.15, which is the…

The system created in ultrarelativistic nuclear collisions is known to behave as an almost ideal liquid. In noncentral collisions, because of the large orbital momentum, such a system might be the fluid with the highest vorticity ever created under laboratory conditions. Particles emerging from such a highly vorticous fluid are expected to be globally polarized with their spins on average pointing along the system angular momentum. Vorticity-induced polarization is the same for particles and antiparticles, but the intense magnetic field generated in these collisions may lead to the splitting in polarization. In this paper we outline the thermal approach to the calculation of the global polarization phenomenon for particles with spin and we discuss the details of the experimental study of this phenomenon, estimating the effect of feed-down. A general formula is derived for the polarization transfer in two-body decays and, particularly, for strong and electromagnetic decays. We find that accounting for such effects is crucial when extracting vorticity and magnetic field from the…

Off-central relativistic heavy ion collisions impart very large orbital angular momenta onto the quark-gluon plasma, creating a strong vortex in the initial hot fluid and appearing eventually, via spin-vorticity coupling, as particle polarization. From the vorticity field given by a multi-phase transport model the authors compute the global polarization of $\mathrm{\ensuremath{\Lambda}}$ baryons which is in agreement with experimental data. This suggests that the spin of a hadron could provide information on quark-gluon plasma flow.

We explore the impact of nuclear matter saturation on the properties and systematics of finite nuclei across the nuclear chart. By using the ab initio in-medium similarity renormalization group (IM-SRG), we study ground-state energies and charge radii of closed-shell nuclei from $^{4}\mathrm{He}$ to $^{78}\mathrm{Ni}$ based on a set of low-resolution two- and three-nucleon interactions that predict realistic saturation properties. We first investigate in detail the convergence properties of these Hamiltonians with respect to model-space truncations for both two- and three-body interactions. We find one particular interaction that reproduces well the ground-state energies of all closed-shell nuclei studied. As expected from their saturation points relative to this interaction, the other Hamiltonians underbind nuclei but lead to a remarkably similar systematics of ground-state energies. Extending our calculations to complete isotopic chains in the $sd$ and $pf$ shells with the valence-space IM-SRG, the same interaction reproduces not only experimental ground states but…

Chiral effective field theory (EFT) predictions are necessarily truncated at some order in the EFT expansion. Bayesian analysis has been proposed as a means to quantify the theoretical uncertainties that are induced by that truncation, in order to provide a robust statistical comparison with experiment. The authors apply a Bayesian model to an extended set of observables calculated for a class of EFT interactions, and demonstrate that a subset of these potentials are consistent with their statistical model for order-by-order convergence.

Background: Multinucleon transfer in low-energy nucleus-nucleus collisions is proposed as a method of production of yet-unknown neutron-rich nuclei hardly reachable by other methods.Purpose: Modeling of dynamics of nuclear reactions induced by heavy ions in their full complexity of competing reaction channels remains to be a challenging task. The work is aimed at development of such a model and its application to the analysis of multinucleon transfer in deep inelastic collisions of heavy ions leading, in particular, to formation of neutron-rich isotopes in the vicinity of the $N=126$ shell closure.Method: Multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations has been proposed. It is combined with a statistical model for simulation of de-excitation of primary reaction fragments. The model provides a continuous description of the system evolution starting from the well-separated target and projectile in the entrance channel of the reaction up to the formation of final reaction products.Results: A rather complete set of experimental data…

With a Yang-Mills flux-tube initial state and a high-resolution (3+1)D particle-in-cell relativistic (PICR) hydrodynamics simulation, we calculate the $\mathrm{\ensuremath{\Lambda}}$ polarization for different energies. The origination of polarization in high energy collisions is discussed, and we find linear impact parameter dependence of the global $\mathrm{\ensuremath{\Lambda}}$ polarization. Furthermore, the global $\mathrm{\ensuremath{\Lambda}}$ polarization in our model decreases very quickly in the low energy domain, and the decline curve fits well the recent results of Beam Energy Scan (BES) program launched by the STAR Collaboration at the Relativistic Heavy Ion Collider (RHIC). The time evolution of polarization is also discussed.

The production of ground-state and excited bottomonia in ultrarelativistic heavy-ion collisions is investigated within a kinetic-rate equation approach including regeneration. We augment our previous calculations by an improved treatment of medium effects, with temperature-dependent binding energies and pertinent reaction rates, $B$-meson resonance states in the equilibrium limit near the hadronization temperature, and a lattice-QCD based equation of state for the bulk medium. In addition to the centrality dependence of the bottomonium yields, we compute their transverse-momentum (${p}_{T}$) spectra and elliptic flow with momentum-dependent reaction rates and a regeneration component based on $b$-quark spectra from a nonperturbative transport model of heavy-quark diffusion. The latter has noticeable consequences for the shape of the bottomonium ${p}_{T}$ spectra. We quantify how uncertainties in the various modeling components affect the predictions for observables. Based on this we argue that the $\mathrm{\ensuremath{\Upsilon}}(1S)$ suppression is a promising observable for mapping…

We describe the propagation of charm quarks in the quark-gluon plasma (QGP) by means of a Boltzmann transport approach. Nonperturbative interaction between heavy quarks and light quarks have been taken into account through a quasiparticle approach in which light partons are dressed with thermal masses tuned to lattice quantum chromodynamics (lQCD) thermodynamics. Such a model is able to describe the main feature of the nonperturbative dynamics: the enhancement of the interaction strength near ${T}_{c}$. We show that the resulting charm in-medium evolution is able to correctly predict simultaneously the nuclear suppression factor, ${R}_{\text{AA}}$, and the elliptic flow, ${v}_{2}$, at both Relativistic Heavy Ion Collider and Large Hadron Collider (LHC) energies and at different centralities. The hadronization of charm quarks is described by mean of an hybrid model of fragmentation plus coalescence and plays a key role toward the agreement with experimental data. We also performed calculations within the Langevin approach, which can lead to very similar ${R}_{\text{AA}}({p}_{T})$ as…

Using a chiral kinetic approach based on initial conditions from a multiphase transport model, we study the spin polarizations of quarks and antiquarks in noncentral heavy ion collisions at the BNL Relativistic Heavy Ion Collider. Because of the nonvanishing vorticity field in these collisions, quarks and antiquarks are found to acquire appreciable spin polarizations in the direction perpendicular to the reaction plane. Converting quarks and antiquarks to hadrons via the coalescence model, we further calculate the spin polarizations of $\mathrm{\ensuremath{\Lambda}}$ and anti-$\mathrm{\ensuremath{\Lambda}}$ hyperons and find their values comparable to those measured in experiments by the STAR Collaboration.

The authors develop a coupled jet-fluid model that includes interactions between jets and a fluid medium in a heavy-ion collision. The model treats both the effect of the medium on the jet shower as well as the back-reaction of this energy deposition on the medium itself. The authors show how the energy that is lost by a jet is deposited in and evolves with the medium, and how that deposited energy might appear in measured observables.

Inclusive jet spectra from $pp$ and PbPb collisions at a nucleon-nucleon center-of-mass energy of $2.76\phantom{\rule{0.16em}{0ex}}\text{TeV}$, collected with the CMS detector at the CERN Large Hadron Collider, are presented. Jets are reconstructed with three different distance parameters ($R=0.2$, 0.3, and 0.4) for transverse momentum (${p}_{\mathrm{T}}$) greater than $70\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}/\mathrm{c}$ and pseudorapidity $|\ensuremath{\eta}|<2$. Next-to-leading-order quantum chromodynamic calculations with nonperturbative corrections are found to overpredict jet production cross sections in $pp$ for small distance parameters. The jet nuclear modification factors for PbPb compared to $pp$ collisions, show a steady decrease from peripheral to central events, along with a weak dependence on the jet ${p}_{\mathrm{T}}$. They are found to be independent of the distance parameter in the measured kinematic range.

Background: The recent accurate measurement of the mass of two pulsars close to or above $2\phantom{\rule{0.16em}{0ex}}{\mathrm{M}}_{\ensuremath{\bigodot}}$ has raised the question of whether such large pulsar masses allow for the existence of exotic degrees of freedom, such as hyperons, inside neutron stars.Purpose: In the present work, we will investigate, within a phenomenological relativistic mean field approach, how the existing hypernuclei properties may constrain the neutron star equation of state and confront the neutron star maximum masses obtained with equations of state calibrated to hypernuclei properties with the astrophysical $2\phantom{\rule{0.16em}{0ex}}{\mathrm{M}}_{\ensuremath{\bigodot}}$ constraint.Method: The study is performed using a relativistic mean field approach to describe both the hypernuclei and the neutron star equations of state. Unified equations of state are obtained. A set of five models that describe $2\phantom{\rule{0.16em}{0ex}}{\mathrm{M}}_{\ensuremath{\bigodot}}$ when only nucleonic degrees of freedom are employed. Some of these models also…

The equation of state (EOS) of dense matter is an essential ingredient for numerical simulations of core-collapse supernovae and neutron star mergers. The properties of matter near and above nuclear saturation density are uncertain, which translates into uncertainties in astrophysical simulations and their multimessenger signatures. Therefore, a wide range of EOSs spanning the allowed range of nuclear interactions are necessary for determining the sensitivity of these astrophysical phenomena and their signatures to variations in input microphysics. We present a new set of finite temperature EOSs based on experimentally allowed Skyrme forces. We employ a liquid-drop model of nuclei to capture the nonuniform phase of nuclear matter at subsaturation density, which is blended into a nuclear statistical equilibrium EOS at lower densities. We also provide a new, open-source code for calculating EOSs for arbitrary Skyrme parametrizations. We then study the effects of different Skyrme parametrizations on thermodynamical properties of dense astrophysical matter, the neutron star mass-radius…

Background: Binding energies and charge radii are fundamental properties of atomic nuclei. When inspecting their particle-number dependence, both quantities exhibit pronounced odd-even staggering. While the odd-even effect in binding energy can be attributed to nucleonic pairing, the origin of staggering in charge radii is less straightforward to ascertain.Purpose: In this work, we study the odd-even effect in binding energies and charge radii, and systematic behavior of differential radii, to identify the underlying components of the effective nuclear interaction.Method: We apply nuclear density functional theory using a family of Fayans and Skyrme energy density functionals fitted to similar data sets but using different optimization protocols. We inspect various correlations between differential charge radii, odd-even staggering in energies and radii, and nuclear matter properties. The Fayans functional is assumed to be in the local ${\mathrm{FaNDF}}^{0}$ form. Detailed analysis is carried out for medium-mass and heavy semimagic nuclei with a particular focus on the Ca…

The production of ${K}^{*}{(892)}^{0}$ and $\ensuremath{\phi}(1020)$ mesons in proton-proton ($pp$) and lead-lead (Pb-Pb) collisions at $\sqrt{{s}_{\mathit{NN}}}=2.76\phantom{\rule{4pt}{0ex}}\mathrm{TeV}$ has been analyzed using a high luminosity data sample accumulated in 2011 with the ALICE detector at the Large Hadron Collider (LHC). Transverse momentum (${p}_{\mathrm{T}}$) spectra have been measured for ${K}^{*}{(892)}^{0}$ and $\ensuremath{\phi}(1020)$ mesons via their hadronic decay channels for ${p}_{\mathrm{T}}$ up to $20\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$. The measurements in $pp$ collisions have been compared to model calculations and used to determine the nuclear modification factor and particle ratios. The ${K}^{*}{(892)}^{0}/K$ ratio exhibits significant reduction from $pp$ to central Pb-Pb collisions, consistent with the suppression of the ${K}^{*}{(892)}^{0}$ yield at low ${p}_{\mathrm{T}}$ due to rescattering of its decay products in the hadronic phase. In central Pb-Pb collisions the ${p}_{\mathrm{T}}$ dependent $\ensuremath{\phi}(1020)/\ensuremath{\pi}$ and…

We compute from chiral two- and three-nucleon interactions the energy per particle of symmetric nuclear matter and pure neutron matter at third-order in perturbation theory including self-consistent second-order single-particle energies. Particular attention is paid to the third-order particle-hole ring diagram, which is often neglected in microscopic calculations of the equation of state. We provide semianalytic expressions for the direct terms from central and tensor model-type interactions that are useful as theoretical benchmarks. We investigate uncertainties arising from the order-by-order convergence in both many-body perturbation theory and the chiral expansion. Including also variations in the resolution scale at which nuclear forces are resolved, we provide new error bands on the equation of state, the isospin-asymmetry energy, and its slope parameter. We find in particular that the inclusion of third-order diagrams reduces the theoretical uncertainty at low densities, while in general the largest error arises from omitted higher-order terms in the chiral expansion of the…

Multiparticle azimuthal cumulants, often used to study collective flow in high-energy heavy-ion collisions, have recently been applied in small collision systems such as $pp$ and $p+A$ to extract the second-order azimuthal harmonic flow ${v}_{2}$. Recent observation of four-, six-, and eight-particle cumulants with ``correct sign'' ${c}_{2}{4}<0$, ${c}_{2}{6}>0$, ${c}_{2}{8}<0$ and approximate equality of the inferred single-particle harmonic flow, ${v}_{2}{4}\ensuremath{\approx}{v}_{2}{6}\ensuremath{\approx}{v}_{2}{8}$, have been used as strong evidence for a collective emission of all the soft particles produced in the collisions. We show that these relations in principle could be violated due to the non-Gaussianity in the event-by-event fluctuation of flow and/or nonflow. Furthermore, we show, using $pp$ events generated with the pythia model, that ${c}_{2}{2k}$ obtained with the standard cumulant method are dominated by nonflow from dijets. An alternative cumulant method based on two or more $\ensuremath{\eta}$-separated subevents is proposed to suppress the dijet contribution.…

We develop a set of kinetic equations for hydrodynamic fluctuations which are equivalent to nonlinear hydrodynamics with noise. The hydrokinetic equations can be coupled to existing second-order hydrodynamic codes to incorporate the physics of these fluctuations. We first show that the kinetic response precisely reproduces the renormalization of the shear viscosity and the fractional power $(\ensuremath{\propto}{\ensuremath{\omega}}^{3/2})$ which characterizes equilibrium correlators of energy and momentum for a static fluid. Then we use the hydrokinetic equations to analyze thermal fluctuations for a Bjorken expansion, evaluating the contribution of thermal noise from the earliest moments and at late times. In the Bjorken case, the solution to the kinetic equations determines the coefficient of the first fractional power of the gradient expansion $(\ensuremath{\propto}1/{(\ensuremath{\tau}T)}^{3/2})$ for the expanding system. Numerically, we find that the contribution to the longitudinal pressure from hydrodynamic fluctuations is larger than second-order hydrodynamics for typical…

The Pauli exclusion principle induces a repulsion between composite systems of identical fermions such as colliding atomic nuclei. Our goal is to study how heavy-ion fusion is impacted by this ``Pauli repulsion.'' We propose a new microscopic approach, the density-constrained frozen Hartree-Fock method, to compute the bare potential including the Pauli exclusion principle exactly. Pauli repulsion is shown to be important inside the barrier radius and increases with the charge product of the nuclei. Its main effect is to reduce tunneling probability. Pauli repulsion is part of the solution to the long-standing deep sub-barrier fusion hindrance problem.

Collective behavior has been observed in hadronic measurements of high multiplicity $\text{proton}+\text{lead}$ collisions at the Large Hadron Collider, as well as in (proton, deuteron, helium-3) + gold collisions at the Relativistic Heavy Ion Collider. To better understand the evolution dynamics and the properties of the matter created in these small systems, a systematic study of the soft hadronic observables together with electromagnetic radiation from these collisions is performed by using a hydrodynamic framework. Quantitative agreement is found between theoretical calculations and existing experimental hadronic observables. The validity of the fluid-dynamical description is estimated by calculating Knudsen and inverse Reynolds numbers. Sizeable thermal yields are predicted for low-${p}_{T}$ photons. Further predictions of higher-order charged hadron anisotropic flow coefficients and of thermal photon enhancement are proposed.

ATLAS measurements of two-particle correlations are presented for $\sqrt{s}=5.02$ and 13 TeV $pp$ collisions and for $\sqrt{{s}_{\mathrm{NN}}}=5.02$ TeV $p+\text{Pb}$ collisions at the LHC. The correlation functions are measured as a function of relative azimuthal angle $\mathrm{\ensuremath{\Delta}}\ensuremath{\phi}$, and pseudorapidity separation $\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}$, using charged particles detected within the pseudorapidity interval $|\ensuremath{\eta}|<2.5$. Azimuthal modulation in the long-range component of the correlation function, with $|\mathrm{\ensuremath{\Delta}}\ensuremath{\eta}|>2$, is studied using a template fitting procedure to remove a ``back-to-back'' contribution to the correlation function that primarily arises from hard-scattering processes. In addition to the elliptic, $\mathrm{cos}(2\mathrm{\ensuremath{\Delta}}\ensuremath{\phi})$, modulation observed in a previous measurement, the $pp$ correlation functions exhibit significant $\mathrm{cos}(3\mathrm{\ensuremath{\Delta}}\ensuremath{\phi})$ and…

Background: Since the earliest days of fission, stochastic models have been used to describe and model the process. For a quarter century, numerical solutions of Langevin equations have been used to model fission of highly excited nuclei, where microscopic potential-energy effects have been neglected.Purpose: In this paper I present a Langevin model for the fission of nuclei with low to medium excitation energies, for which microscopic effects in the potential energy cannot be ignored.Method: I solve Langevin equations in a five-dimensional space of nuclear deformations. The macroscopic-microscopic potential energy from a global nuclear structure model well benchmarked to nuclear masses is tabulated on a mesh of approximately ${10}^{7}$ points in this deformation space. The potential is defined continuously inside the mesh boundaries by use of a moving five-dimensional cubic spline approximation. Because of reflection symmetry, the effective mesh is nearly twice this size. For the inertia, I use a (possibly scaled) approximation to the inertia tensor defined by irrotational flow. A…

This work demonstrates that the ``standard model'' of heavy ion collisions, starting with initial-state fluctuations, followed by viscous hydrodynamic expansion, and concluding with conversion to hadrons that undergo rescattering and resonance decays, describes data at the highest LHC energy.

In this work we present a newly constructed equation of state (EoS), applicable to stellar core collapse and neutron star mergers including the entire baryon octet. Our EoS is compatible with the main constraints from nuclear physics and, in particular, with a maximum mass for cold $\ensuremath{\beta}$-equilibrated neutron stars of $2{M}_{\ensuremath{\bigodot}}$ in agreement with recent observations. As an application of our new EoS, we compute numerical stationary models for rapidly (rigidly) rotating hot neutron stars. We consider maximum masses of hot stars, such as protoneutron stars or hypermassive neutron stars in the postmerger phase of binary neutron star coalescence. The universality of $I\text{\ensuremath{-}}Q$ relations at nonzero temperature for fast rotating models, comparing a purely nuclear EoS with its counterparts containing $\mathrm{\ensuremath{\Lambda}}$ hyperons or the entire baryon octet, respectively, is discussed, too. We find that the $I\text{\ensuremath{-}}Q$ universality is broken in our models when thermal effects become important, independent on the…

The masses of nuclei between the experimentally known region and the neutron drip line are key inputs for a variety of astrophysical applications. Particularly near the drip lines, unstable nuclei are also at the core of fundamental questions about the limits of nuclear binding. The authors use two existing mass models that capture the essential underlying physics and then refine their predictions by training an artificial neural network. The results significantly reduce the root-mean-square deviation relative to experiment. These newly refined mass tables are used to map the neutron drip lines and to study a few critical $r$-process nuclei.

The STAR Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum hadron trigger, in central and peripheral $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{\mathrm{NN}}}=200$ GeV. Charged jets are reconstructed with the anti-${k}_{\mathrm{T}}$ algorithm for jet radii $R$ between 0.2 and 0.5 and with low infrared cutoff of track constituents (${p}_{\mathrm{T}}>0.2 \mathrm{GeV}/\mathrm{c}$). A novel mixed-event technique is used to correct the large uncorrelated background present in heavy ion collisions. Corrected recoil jet distributions are reported at midrapidity, for charged-jet transverse momentum ${p}_{\mathrm{T},\mathrm{jet}}^{\mathrm{ch}}<30 \mathrm{GeV}/\mathrm{c}$. Comparison is made to similar measurements for $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s}=2.76$ TeV, to calculations for $p+p$ collisions at $\sqrt{s}=200$ GeV based on the pythia Monte Carlo generator and on a next-to-leading order perturbative QCD approach, and to theoretical calculations incorporating jet quenching. The…

We present the first application of the newly developed extended Kuo-Krenciglowa (EKK) theory of the effective nucleon-nucleon interaction to shell-model studies of exotic nuclei, including those where conventional approaches with fitted interactions encounter difficulties. This EKK theory enables us to derive an interaction that is suitable for several major shells $(sd+pf$ in this work). By using such an effective interaction obtained from the Entem-Machleidt QCD-based $\ensuremath{\chi}{\mathrm{N}}^{3}\mathrm{LO}$ interaction and the Fujita-Miyazawa three-body force, the energies, $E2$ properties, and spectroscopic factors of low-lying states of neutron-rich Ne, Mg, and Si isotopes are nicely described, as the first shell-model description of the ``island of inversion'' without fit of the interaction. The long-standing question as to how particle-hole excitations occur across the $sd\text{\ensuremath{-}}pf$ magic gap is clarified with distinct differences from the conventional approaches. The shell evolution is shown to appear similarly to earlier studies.

The multinucleon transfer reaction has been investigated within the dinuclear system model. The nucleon transfer is coupled to the dissipation of relative motion energy and angular momentum by solving a set of microscopically derived master equations. A barrier distribution approach is implemented in the model in order to include the contributions of different orientations and dynamical effects. The available data of fragment production via multinucleon transfer reactions could be understood with the model for the reactions of $^{136}\mathrm{Xe}+^{198}\mathrm{Pt}/^{208}\mathrm{Pb}$ near Coulomb barrier energies. It is found that the production of heavy neutron-rich nuclei weakly depends on the incident energy. However, the yields of proton-rich nuclei increase with the incident energy.

We develop a method to construct a microscopic optical potential from chiral interactions for nucleon-nucleus scattering. The optical potential is constructed by combining the Green's function approach with the coupled-cluster method. To deal with the poles of the Green's function along the real energy axis we employ a Berggren basis in the complex energy plane combined with the Lanczos method. Using this approach, we perform a proof-of-principle calculation of the optical potential for the elastic neutron scattering on $^{16}\mathrm{O}$. For the computation of the ground state of $^{16}\mathrm{O}$, we use the coupled-cluster method in the singles-and-doubles approximation, while for the $A\ifmmode\pm\else\textpm\fi{}1$ nuclei we use particle-attached/removed equation-of-motion method truncated at two-particle--one-hole and one-particle--two-hole excitations, respectively. We verify the convergence of the optical potential and scattering phase shifts with respect to the model-space size and the number of discretized complex continuum states. We also investigate the absorptive…

We extend our virial approach to study the neutral-current neutrino response of nuclear matter at low densities. In the long-wavelength limit, the virial expansion makes model-independent predictions for neutrino-nucleon scattering rates and the density ${S}_{V}$ and spin ${S}_{A}$ responses. We find that ${S}_{A}$ is significantly reduced from one even at low densities. We provide a simple fit ${S}_{A}^{f}(n,T,{Y}_{p})$ of the axial response as a function of density $n$, temperature $T$, and proton fraction ${Y}_{p}$, which can be incorporated into supernova simulations in a straightforward manner. This fit reproduces our virial results at low densities and the Burrows and Sawyer random-phase approximation (RPA) model calculations at high densities. Preliminary one-dimensional supernova simulations suggest that the virial reduction in the axial response may enhance neutrino heating rates in the gain region during the accretion phase of a core-collapse supernovae.

Background: Interest in the behavior of nucleon electromagnetic form factors at large momentum transfers has steadily increased since the discovery, using polarization observables, of the rapid decrease of the ratio ${G}_{E}^{p}/{G}_{M}^{p}$ of the proton's electric and magnetic form factors for momentum transfers ${Q}^{2}\ensuremath{\gtrsim}1$ ${\mathrm{GeV}}^{2}$, in strong disagreement with previous extractions of this ratio using the traditional Rosenbluth separation technique.Purpose: The GEp-III and $\mathrm{GEp}\text{\ensuremath{-}}2\ensuremath{\gamma}$ experiments were carried out in Jefferson Laboratory's (JLab's) Hall C from 2007 to 2008, to extend the knowledge of ${G}_{E}^{p}/{G}_{M}^{p}$ to the highest practically achievable ${Q}^{2}$ given the maximum beam energy of 6 GeV and to search for effects beyond the Born approximation in polarization transfer observables of elastic $\stackrel{P\vec}{e}p$ scattering. This article provides an expanded description of the common experimental apparatus and data analysis procedures, and reports the results of a final reanalysis of…

We present a microscopic calculation of $\ensuremath{\alpha}$-cluster formation in heavy nuclei by using the quartetting wave function approach. The interaction of the quartet with the core nucleus is taken in local density approximation. The $\ensuremath{\alpha}$-cluster formation is found to be particularly sensitive to the interplay of the mean field felt by the $\ensuremath{\alpha}$-cluster and the Pauli blocking as a consequence of antisymmetrization. The striking feature of $\ensuremath{\alpha}$-cluster formation probability across the major shell closures of 82 protons and 126 neutrons is reproduced. The shell (or subshell) effects on the $\ensuremath{\alpha}$-cluster formation in superheavy nuclei are also analyzed.

The authors present a detailed report on quantum Monte Carlo (QMC) calculations of light nuclei with local two- and three-body interactions from chiral effective field theory. They establish QMC methods with local chiral interactions as a versatile and systematic approach to $a\phantom{\rule{0}{0ex}}b-i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations of light nuclei.

We show that in the three-polytrope model of Hebeler et al. [Astrophys. J. 773, 11 (2013)] for the neutron star equation of state (EoS) at supersaturation densities a third family of compact stars can be obtained which confirms the possibility of high-mass twin stars that have coincident masses ${M}_{1}={M}_{2}\ensuremath{\approx}2{M}_{\ensuremath{\bigodot}}$ and significantly different radii $|{R}_{1}\ensuremath{-}{R}_{2}|>2--3$ km. We show that the causality constraint puts severe limitations on the maximum mass of the third family sequence which can be relaxed when this scheme is extended to four polytropes thus mimicking a realistic high-density matter EoS.

We present the formalism for consistently transforming transition operators within the in-medium similarity renormalization group framework. We implement the operator transformation in both the equations-of-motion and valence-space variants, and present first results for electromagnetic transitions and moments in medium-mass nuclei using consistently evolved operators, including the induced two-body parts. These results are compared to experimental values, and---where possible---the results of no-core shell-model calculations using the same input chiral interaction. We find good agreement between the equations-of-motion and valence-space approaches. Magnetic dipole observables are generally in reasonable agreement with experiment, while the more collective electric quadrupole and octupole observables are significantly underpredicted, often by over an order of magnitude, indicating missing physics at the present level of truncation.

We developed a four-dimensional (4D) Langevin model, which can treat the deformation of each fragment independently and applied it to low-energy fission of $^{236}\mathrm{U}$, the compound system of the reaction $n+^{235}\mathrm{U}$. The potential energy is calculated with the deformed two-center Woods-Saxon (TCWS) and the Nilsson-type potential with the microscopic energy corrections following the Strutinsky method and BCS pairing. The transport coefficients are calculated by macroscopic prescriptions. It turned out that the deformation for the light and heavy fragments behaves differently, showing a sawtooth structure similar to that of the neutron multiplicities of the individual fragments $\ensuremath{\nu}(A)$. Furthermore, the measured total kinetic energy $\mathrm{TKE}(A)$ and its standard deviation are reproduced fairly well by the 4D Langevin model based on the TCWS potential in addition to the fission fragment mass distributions. The developed model allows a multiparametric correlation analysis among, e.g., the three key fission observables, mass, TKE, and neutron…

Background:The discovery of neutrinoless double-$\ensuremath{\beta}$ ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) decay would demonstrate the nature of neutrinos, have profound implications for our understanding of matter-antimatter mystery, and solve the mass hierarchy problem of neutrinos. The calculations for the nuclear matrix elements ${M}^{0\ensuremath{\nu}}$ of $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay are crucial for the interpretation of this process.Purpose: We study the effects of relativity and nucleon-nucleon short-range correlations on the nuclear matrix elements ${M}^{0\ensuremath{\nu}}$ by assuming the mechanism of exchanging light or heavy neutrinos for the $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay.Methods:The nuclear matrix elements ${M}^{0\ensuremath{\nu}}$ are calculated within the framework of covariant density functional theory, where the beyond-mean-field correlations are included in the nuclear wave functions by configuration mixing of both angular-momentum and particle-number projected quadrupole deformed…

The modification of hard jets in an extended static medium held at a fixed temperature is studied using three different Monte Carlo event generators: linear Boltzmann transport (LBT), modular all twist transverse-scattering elastic-drag and radiation (MATTER), and modular algorithm for relativistic treatment of heavy-ion interactions (MARTINI). Each event generator contains a different set of assumptions regarding the energy and virtuality of the partons within a jet versus the energy scale of the medium and, hence, applies to a different epoch in the space-time history of the jet evolution. Here modeling is developed where a jet may sequentially transition from one generator to the next, on a parton-by-parton level, providing a detailed simulation of the space-time evolution of medium modified jets over a much broader dynamic range than has been attempted previously in a single calculation. Comparisons are carried out for different observables sensitive to jet quenching, including the parton fragmentation function and the azimuthal distribution of jet energy around the jet axis.…

The string melting version of a multi-phase transport model is often applied to high-energy heavy-ion collisions since the dense matter thus formed is expected to be in parton degrees of freedom. In this work we improve its quark coalescence component, which describes the hadronization of the partonic matter to a hadronic matter. We removed the previous constraint that forced the numbers of mesons, baryons, and antibaryons in an event to be separately conserved through the quark coalescence process. A quark now could form either a meson or a baryon depending on the distance to its coalescence partner(s). We then compare results from the improved model with the experimental data on hadron $dN/dy,\phantom{\rule{0.16em}{0ex}}{p}_{{}_{\mathrm{T}}}$ spectra, and ${v}_{2}$ in heavy-ion collisions from $\sqrt{{s}_{{}_{\mathrm{NN}}}}=62.4$ GeV to 5.02 TeV. We show that, besides being able to describe these observables for low-${p}_{{}_{\mathrm{T}}}$ pions and kaons, the improved model also better describes the low-${p}_{{}_{\mathrm{T}}}$ baryon observables in general, especially the baryon…

Static and dynamic aspects of the fission process of $^{226}\mathrm{Th}$ are analyzed in a self-consistent framework based on relativistic energy density functionals. Constrained relativistic mean-field calculations in the collective space of axially symmetric quadrupole and octupole deformations, based on the energy density functional PC-PK1 and a $\ensuremath{\delta}$-force pairing, are performed to determine the potential energy surface of the fissioning nucleus, the scission line, the single-nucleon wave functions, energies, and occupation probabilities, as functions of deformation parameters. Induced fission dynamics is described using the time-dependent generator coordinate method in the Gaussian overlap approximation. A collective Schr\"odinger equation, determined entirely by the microscopic single-nucleon degrees of freedom, propagates adiabatically in time the initial wave packet built by boosting the ground-state solution of the collective Hamiltonian for $^{226}\mathrm{Th}$. The position of the scission line and the microscopic input for the collective Hamiltonian are…

Using a new approximate analytic parameter-free proxy-SU(3) scheme, we make simple predictions of shape observables for deformed nuclei, namely $\ensuremath{\gamma}$ and $\ensuremath{\beta}$ deformation variables, the global feature of prolate dominance, and the locus of the prolate-oblate shape transition. The predictions are compared with empirical results.

Elliptic flow, ${v}_{2}$, and triangular flow, ${v}_{3}$, are to a good approximation linearly proportional to the corresponding spatial anisotropies of the initial density profile, ${\ensuremath{\varepsilon}}_{2}$ and ${\ensuremath{\varepsilon}}_{3}$. Using event-by-event hydrodynamic simulations, we point out when deviations from this linear scaling are to be expected. When these deviations are negligible, relative ${v}_{n}$ fluctuations are equal to relative ${\ensuremath{\varepsilon}}_{n}$ fluctuations, and one can directly probe models of initial conditions using ratios of cumulants, for instance ${v}_{n}{4}/{v}_{n}{2}$. We argue that existing models of initial conditions tend to overestimate flow fluctuations in central Pb + Pb collisions, and to underestimate them in peripheral collisions. We make predictions for ${v}_{3}{6}$ in noncentral Pb + Pb collisions, and for ${v}_{3}{4}$ and ${v}_{3}{6}$ in high-multiplicity $p+\text{Pb}$ collisions.

Background: Microscopic calculations of heavy nuclei face considerable difficulties due to the sizes of the matrices that need to be solved. Various approximation schemes have been invoked, for example by truncating the spaces, imposing seniority limits, or appealing to various symmetry schemes such as pseudo-SU(3). This paper proposes a new symmetry scheme also based on SU(3). This proxy-SU(3) can be applied to well-deformed nuclei, is simple to use, and can yield analytic predictions.Purpose: To present the new scheme and its microscopic motivation, and to test it using a Nilsson model calculation with the original shell model orbits and with the new proxy set.Method: We invoke an approximate, analytic, treatment of the Nilsson model, that allows the above vetting and yet is also transparent in understanding the approximations involved in the new proxy-SU(3).Results: It is found that the new scheme yields a Nilsson diagram for well-deformed nuclei that is very close to the original Nilsson diagram. The specific levels of approximation in the new scheme are also shown, for each…

Background: The possibility that an unconventional depletion (referred to as a ``bubble'') occurs in the center of the charge density distribution of certain nuclei due to a purely quantum mechanical effect has attracted theoretical and experimental attention in recent years. Based on a mean-field rationale, a correlation between the occurrence of such a semibubble and an anomalously weak splitting between low angular-momentum spin-orbit partners has been further conjectured. Energy density functional and valence-space shell model calculations have been performed to identify and characterize the best candidates, among which $^{34}\mathrm{Si}$ appears as a particularly interesting case. While the experimental determination of the charge density distribution of the unstable $^{34}\mathrm{Si}$ is currently out of reach, $(d,p)$ experiments on this nucleus have been performed recently to test the correlation between the presence of a bubble and an anomalously weak $1/{2}^{\ensuremath{-}}\text{\ensuremath{-}}3/{2}^{\ensuremath{-}}$ splitting in the spectrum of $^{35}\mathrm{Si}$ as…

The self-consistent quasiparticle random-phase approximation (QRPA) approach is formulated in the canonical single-nucleon basis of the relativistic Hatree--Fock--Bogoliubov (RHFB) theory. This approach is applied to study the isobaric analog states (IASs) and Gamow--Teller resonances (GTRs) by taking Sn isotopes as examples. It is found that self-consistent treatment of the particle-particle residual interaction is essential to concentrate the IAS in a single peak for open-shell nuclei and the Coulomb exchange term is very important to predict the IAS energies. For the GTR, the isovector pairing can increase the calculated GTR energy, while the isoscalar pairing has an important influence on the low-lying tail of the Gamow--Teller transition.

The $^{13}\mathrm{C}(^{18}\mathrm{O},^{16}\mathrm{O})^{15}\mathrm{C}$ reaction is studied at 84 MeV incident energy. Excitation energy spectra and absolute cross-section angular distributions for the strongest transitions are measured with good energy and angular resolutions. Strong selectivity for two-neutron configurations in the states of the residual nucleus is found. The measured cross-section angular distributions are analyzed by exact finite-range coupled reaction channel calculations. The two-particle wave functions are extracted using the extreme cluster and the independent coordinate scheme with shell-model derived coupling strengths. A new approach also is introduced, the microscopic cluster, in which the spectroscopic amplitudes in the center-of-mass reference frame are derived from shell-model calculations using the Moshinsky transformation brackets. This new model is able to describe well the experimental cross section and to highlight cluster configurations in the involved wave functions.

An improved semi-empirical relationship for $\ensuremath{\alpha}$-decay half-lives is proposed by introducing a precise radius formula and an analytic expression for preformation probability. By using the improved relationship, the $\ensuremath{\alpha}$-decay half-lives of 421 nuclei are calculated. It is shown that the accuracy of this semi-empirical relationship is improved significantly compared to its predecessor. Further research shows that it also reproduces the experimental half-lives of the superheavy nuclei well. Last, with the improved formula the $\ensuremath{\alpha}$-decay half-lives of the $Z=118--121$ isotopes are predicted, which are helpful for future experiments. In addition, there is a prediction of a magic number effect at $N=184$.

We derive the charged current absorption rate of electron and antielectron neutrinos in dense matter using a fully relativistic approach valid at arbitrary matter degeneracy. We include mean field energy shifts due to nuclear interactions and the corrections due to weak magnetism. The rates are derived both from the familiar Fermi's golden rule and from the techniques of finite temperature field theory, and are shown to be equivalent. In various limits, these results can also be used to calculate neutral current opacities. We find that some pieces of the response have been left out in previous derivations and their contribution at high density can be significant. Useful formulas and detailed derivations are presented and we provide a new open-source implementation of these opacities for use in radiation hydrodynamic simulations of core-collapse supernovae and neutron star mergers.