The 50 most-cited articles in Physical Review C, 2018

Global polarization of $\mathrm{\ensuremath{\Lambda}}$ hyperons has been measured to be of the order of a few tenths of a percentage in Au+Au collisions at $\sqrt{{s}_{{}_{NN}}}$ = 200 GeV, with no significant difference between $\mathrm{\ensuremath{\Lambda}}$ and $\overline{\mathrm{\ensuremath{\Lambda}}}$. These new results reveal the collision energy dependence of the global polarization together with the results previously observed at $\sqrt{{s}_{{}_{NN}}}$ = 7.7--62.4 GeV and indicate noticeable vorticity of the medium created in noncentral heavy-ion collisions at the highest Relativistic Heavy Ion Collider collision energy. The signal is in rough quantitative agreement with the theoretical predictions from a hydrodynamic model and from a multi-phase transport model. The polarization is larger in more peripheral collisions, and depends weakly on the hyperon's transverse momentum and pseudorapidity ${\ensuremath{\eta}}^{H}$ within $|{\ensuremath{\eta}}^{H}|<1$. An indication of the polarization dependence on the event-by-event charge asymmetry is observed at the…

The detection of gravitational waves from the neutron-star merger GW170817 provided the first firm observational constraint on the radius of neutron stars---nature's densest visible objects. The authors find that modern nuclear-physics-based calculations of the equation of state of dense neutron-rich matter predict radii that are compatible but more restrictive. They critically examine associated uncertainties and determine how improved constraints from future observations can provide new insights into dense matter and possible phase transitions in the neutron-star core.

Metamodeling for the nucleonic equation of state (EOS), inspired from a Taylor expansion around the saturation density of symmetric nuclear matter, is proposed and parameterized in terms of the empirical parameters. The present knowledge of nuclear empirical parameters is first reviewed in order to estimate their average values and associated uncertainties, and thus defining the parameter space of the metamodeling. They are divided into isoscalar and isovector types, and ordered according to their power in the density expansion. The goodness of the metamodeling is analyzed against the predictions of the original models. In addition, since no correlation among the empirical parameters is assumed a priori, all arbitrary density dependences can be explored, which might not be accessible in existing functionals. Spurious correlations due to the assumed functional form are also removed. This meta-EOS allows direct relations between the uncertainties on the empirical parameters and the density dependence of the nuclear equation of state and its derivatives, and the mapping between the two…

Constraints set on key parameters of the nuclear matter equation of state (EoS) by the values of the tidal deformability, inferred from GW170817, are examined by using a diverse set of relativistic and nonrelativistic mean-field models. These models are consistent with bulk properties of finite nuclei as well as with the observed lower bound on the maximum mass of neutron star $\ensuremath{\approx}2{M}_{\ensuremath{\bigodot}}$. The tidal deformability shows a strong correlation with specific linear combinations of the isoscalar and isovector nuclear matter parameters associated with the EoS. Such correlations suggest that a precise value of the tidal deformability can put tight bounds on several EoS parameters, in particular on the slope of the incompressibility and the curvature of the symmetry energy. The tidal deformability obtained from the GW170817 and its UV, optical and infrared counterpart sets the radius of a canonical $1.4{M}_{\ensuremath{\bigodot}}$ neutron star to be $11.82\ensuremath{\le}{R}_{1.4}\ensuremath{\le}13.72\phantom{\rule{4pt}{0ex}}\mathrm{km}$.

We present the results of an improved Monte Carlo Glauber (MCG) model of relevance for collisions involving nuclei at center-of-mass energies of the BNL Relativistic Heavy Ion Collider ($\sqrt{{s}_{\mathit{NN}}}=0.2$ TeV), CERN Large Hadron Collider (LHC) ($\sqrt{{s}_{\mathit{NN}}}=2.76--8.8\phantom{\rule{0.16em}{0ex}}\mathrm{TeV}$), and proposed future hadron colliders ($\sqrt{{s}_{\mathit{NN}}}\ensuremath{\approx}10--63$ TeV). The inelastic $pp$ cross sections as a function of $\sqrt{{s}_{\mathit{NN}}}$ are obtained from a precise data-driven parametrization that exploits the many available measurements at LHC collision energies. We describe the nuclear density of a lead nucleus with two separated two-parameter Fermi distributions for protons and neutrons to account for their different densities close to the nuclear periphery. Furthermore, we model the nucleon degrees of freedom inside the nucleus through a lattice with a minimum nodal separation, combined with a ``recentering and reweighting'' procedure, that overcomes some limitations of previous MCG approaches. The nuclear…

Using the conservation laws for charge, energy, momentum, and angular momentum, we derive hydrodynamic equations for the charge density, local temperature, and fluid velocity, as well as for the polarization tensor, starting from local equilibrium distribution functions for particles and antiparticles with spin $1/2$. The resulting set of differential equations extends the standard picture of perfect-fluid hydrodynamics with a conserved entropy current in a minimal way. This framework can be used in space-time analyses of the evolution of spin and polarization in various physical systems including high-energy nuclear collisions. We demonstrate that a stationary vortex, which exhibits vorticity-spin alignment, corresponds to a special solution of the spin-hydrodynamical equations.

The next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double-$\ensuremath{\beta}$ ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) decay in $^{136}\mathrm{Xe}$ with a target half-life sensitivity of approximately ${10}^{28}$ yr using $5\ifmmode\times\else\texttimes\fi{}{10}^{3}$ kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the $^{136}\mathrm{Xe}$ mass, the monolithic and homogeneous configuration of the active medium, and the multiparameter measurements of the interactions enabled by the time projection chamber. The detector concept and anticipated performance are presented based upon demonstrated realizable background rates.

The Bayesian statistical approaches have a recognized utility in improving the quantified predictions for nuclear masses away from stability that provide key inputs for a variety of astrophysical applications. The present paper is devoted to the methodology of such efforts. It applies Bayesian Gaussian processes and neural networks to two-neutron separation energies of nuclei. The authors find that Gaussian processes deliver a more stable performance.

We study the local structure of the vorticity field and the $\mathrm{\ensuremath{\Lambda}}$ polarization in Au+Au collisions in the energy range $\sqrt{{s}_{\mathrm{NN}}}=7.7--200\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$ and Pb+Pb collisions at $\sqrt{{s}_{\mathrm{NN}}}=2760\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$ using a multiphase transport model. We focus on the vorticity field arising from the nonuniform expansion of the fireball, which gives the circular structure of the transverse vorticity ${\mathbf{\ensuremath{\omega}}}_{\ensuremath{\perp}}=({\ensuremath{\omega}}_{x},{\ensuremath{\omega}}_{y})$ around the $z$ direction as well as the quadrupole pattern of the longitudinal vorticity ${\ensuremath{\omega}}_{z}$ in the transverse plane. As a consequence, the three components of the polarization vector $\mathbf{P}=({P}_{x},{P}_{y},{P}_{z})$ for $\mathrm{\ensuremath{\Lambda}}$ hyperons show harmonic behaviors as $\mathrm{sgn}(Y)sin{\ensuremath{\phi}}_{p}$, $\ensuremath{-}\mathrm{sgn}(Y)cos{\ensuremath{\phi}}_{p}$, and $\ensuremath{-}sin(2{\ensuremath{\phi}}_{p})$, where…

Valuable theoretical predictions of nuclear dipole excitations in the whole nuclear chart are of great interest for different applications, including in particular nuclear astrophysics. Here we extend our large-scale calculations of the $E1$ and $M1$ absorption $\ensuremath{\gamma}$-ray strength function obtained in the framework of the axially symmetric deformed quasiparticle random-phase approximation (QRPA) based on the finite-range D1M Gogny force to the deexcitation strength function. To do so, shell-model calculations of the deexcitation dipole strength function are performed and their limit at low $\ensuremath{\gamma}$ energies used to complement phenomenologically the QRPA calculations. We compare our final prediction of the $E1$ and $M1$ strength with available experimental data at low energies and show that a fairly good agreement is obtained. Predictions of the dipole strength function for spherical and deformed nuclei within the valley of $\ensuremath{\beta}$ stability as well as in the neutron-rich region are discussed and compared with traditional Lorentzian-type…

Employing recently proposed metamodeling for the nucleonic matter equation of state, we analyze neutron star global properties such as masses, radii, momentum of inertia, and others. The impact of the uncertainty on empirical parameters on these global properties is analyzed in a Bayesian statistical approach. Physical constraints, such as causality and stability, are imposed on the equation of state and different hypotheses for the direct Urca (dUrca) process are investigated. In addition, only metamodels with maximum masses above $2{M}_{\ensuremath{\bigodot}}$ are selected. Our main results are the following: the equation of state exhibits a universal behavior against the dUrca hypothesis under the condition of charge neutrality and $\ensuremath{\beta}$ equilibrium; neutron stars, if composed exclusively of nucleons and leptons, have a radius of $12.7\ifmmode\pm\else\textpm\fi{}0.4$ km for masses ranging from 1 up to $2{M}_{\ensuremath{\bigodot}}$; a small radius lower than 11 km is very marginally compatible with our present knowledge of the nuclear empirical parameters; and…

We present a fully three-dimensional model providing initial conditions for energy and net-baryon density distributions in heavy-ion collisions at arbitrary collision energy. The model includes the dynamical deceleration of participating nucleons or valence quarks, depending on the implementation. The duration of the deceleration continues until the string spanned between colliding participants is assumed to thermalize, which is either after a fixed proper time, or a fluctuating time depending on sampled final rapidities. Energy is deposited in space time along the string, which in general will span a range of space-time rapidities and proper times. We study various observables obtained directly from the initial-state model, including net-baryon rapidity distributions, two-particle rapidity correlations, as well as the rapidity decorrelation of the transverse geometry. Their dependence on the model implementation and parameter values is investigated. We also present the implementation of the model with 3+1-dimensional hydrodynamics, which involves the addition of source terms that…

Studies of fluctuations and correlations of soft hadrons and hard and electromagnetic probes of the dense and strongly interacting medium require event-by-event hydrodynamic simulations of high-energy heavy-ion collisions that are computing intensive. We develop a $(3+1)$-dimensional viscous hydrodynamic model---CLVisc that is parallelized on a graphics processing unit (GPU) by using the open computing language (OpenCL) with 60 times performance increase for spacetime evolution and more than 120 times for the Cooper--Frye particlization relative to that without GPU parallelization. The model is validated with comparisons with different analytic solutions, other existing numerical solutions of hydrodynamics, and experimental data on hadron spectra in high-energy heavy-ion collisions. The pseudorapidity dependence of anisotropic flow ${v}_{n}(\ensuremath{\eta})$ are then computed in CLVisc with initial conditions given by the a multiphase transport (ampt) model, with energy density fluctuations both in the transverse plane and along the longitudinal direction. Although the magnitude…

For the first time, the baryon current and its diffusive effects have been incorporated into one of the 3D relativistic viscous hydrodynamics models, successfully used to describe heavy-ion collisions at the top RHIC energies and at the LHC. This approach will be very useful in the interpretation of data coming from the low-energy Beam Energy Scan (BES) at RHIC, and for the search for a critical point in the QCD phase diagram.

Simulations by transport codes are indispensable to extract valuable physical information from heavy-ion collisions. In order to understand the origins of discrepancies among different widely used transport codes, we compare 15 such codes under controlled conditions of a system confined to a box with periodic boundary, initialized with Fermi-Dirac distributions at saturation density and temperatures of either 0 or 5 MeV. In such calculations, one is able to check separately the different ingredients of a transport code. In this second publication of the code evaluation project, we only consider the two-body collision term; i.e., we perform cascade calculations. When the Pauli blocking is artificially suppressed, the collision rates are found to be consistent for most codes (to within $1%$ or better) with analytical results, or completely controlled results of a basic cascade code. In orderto reach that goal, it was necessary to eliminate correlations within the same pair of colliding particles that can be present depending on the adopted collision prescription. In calculations with…

By applying a Bayesian model-to-data analysis, we estimate the temperature and momentum dependence of the heavy quark diffusion coefficient in an improved Langevin framework. The posterior range of the diffusion coefficient is obtained by performing a Markov chain Monte Carlo random walk and calibrating on the experimental data of $D$-meson ${R}_{\mathrm{AA}}$ and ${v}_{2}$ in three different collision systems at the Relativistic Heavy-Ion Collidaer (RHIC) and the Large Hadron Collider (LHC): Au-Au collisions at 200 GeV and Pb-Pb collisions at 2.76 and 5.02 TeV. The spatial diffusion coefficient is found to be consistent with lattice QCD calculations and comparable with other models' estimation. We demonstrate the capability of our improved Langevin model to simultaneously describe the ${R}_{\mathrm{AA}}$ and ${v}_{2}$ at both RHIC and the LHC energies, as well as the higher order flow coefficient such as $D$ meson ${v}_{3}$. We show that by applying a Bayesian analysis, we are able to quantitatively and systematically study the heavy flavor dynamics in heavy-ion collisions.

We investigate the charge-dependent flow induced by magnetic and electric fields in heavy-ion collisions. We simulate the evolution of the expanding cooling droplet of strongly coupled plasma hydrodynamically, using the iEBE-VISHNU framework, and add the magnetic and electric fields as well as the electric currents they generate in a perturbative fashion. We confirm the previously reported effect of the electromagnetically induced currents [Gursoy et al., Phys. Rev. C 89, 054905 (2014)], that is a charge-odd directed flow $\mathrm{\ensuremath{\Delta}}{v}_{1}$ that is odd in rapidity, noting that it is induced by magnetic fields (\`a la Faraday and Lorentz) and by electric fields (the Coulomb field from the charged spectators). In addition, we find a charge-odd $\mathrm{\ensuremath{\Delta}}{v}_{3}$ that is also odd in rapidity and that has a similar physical origin. We furthermore show that the electric field produced by the net charge density of the plasma drives rapidity-even charge-dependent contributions to the radial flow $\ensuremath{\langle}{p}_{T}\ensuremath{\rangle}$ and the…

Neutron lifetime is one of the most important physical constants: it determines parameters of the weak interaction and predictions of primordial nucleosynthesis theory. There remains the unsolved problem of a 3.9\ensuremath{\sigma} discrepancy between measurements of this lifetime using neutrons in beams and those with stored ultracold neutrons (UCN). In our experiment we measure the lifetime of neutrons trapped by Earth's gravity in an open-topped vessel. Two configurations of the trap geometry are used to change the mean frequency of UCN collisions with the surfaces; this is achieved by plunging an additional surface into the trap without breaking the vacuum. The trap walls are coated with a hydrogen-less fluorine-containing polymer to reduce losses of UCN. The stability of this coating over multiple thermal cycles between 80 and 300 K was tested. At 80 K, the probability of UCN loss due to collisions with the trap walls is just 1.5% of the probability of \ensuremath{\beta} decay. The free neutron lifetime is determined by extrapolation to an infinitely large trap with zero…

In relativistic heavy-ion collisions, the production of heavy quarks at large transverse momenta is strongly suppressed compared to proton-proton collisions. In addition, an unexpectedly large azimuthal anisotropy was observed for the emission of charmed hadrons in noncentral collisions. Both observations pose challenges to the theoretical understanding of the coupling between heavy quarks and the quark-gluon plasma produced in these collisions. Transport models for the evolution of heavy quarks in a QCD medium offer the opportunity to study these effects; two of the most successful approaches are based on the linearized Boltzmann transport equation and the Langevin equation. In this work, we develop a hybrid transport model that combines the strengths of both of these approaches: Heavy quarks scatter with medium partons using matrix-elements calculated in perturbative QCD, while between these discrete hard scatterings they evolve using a Langevin equation with empirical transport coefficients to capture the nonperturbative soft part of the interaction. With the hybrid transport…

Charge-dependent azimuthal correlations of same- and opposite-sign pairs with respect to the second- and third-order event planes have been measured in $p\text{Pb}$ collisions at $\sqrt{{s}_{{}_{\mathrm{NN}}}}=8.16\phantom{\rule{0.28em}{0ex}}\text{TeV}$ and $\text{PbPb}$ collisions at 5.02 TeV with the CMS experiment at the LHC. The measurement is motivated by the search for the charge separation phenomenon predicted by the chiral magnetic effect (CME) in heavy ion collisions. Three- and two-particle azimuthal correlators are extracted as functions of the pseudorapidity difference, the transverse momentum (${p}_{\mathrm{T}}$) difference, and the ${p}_{\mathrm{T}}$ average of same- and opposite-charge pairs in various event multiplicity ranges. The data suggest that the charge-dependent three-particle correlators with respect to the second- and third-order event planes share a common origin, predominantly arising from charge-dependent two-particle azimuthal correlations coupled with an anisotropic flow. The CME is expected to lead to a ${v}_{2}$-independent three-particle correlation…

We argue that relativistic hydrodynamics is able to make robust predictions for soft particle production in Xe+Xe collisions at the CERN Large Hadron Collider (LHC). The change of system size from Pb+Pb to Xe+Xe provides a unique opportunity to test the scaling laws inherent to fluid dynamics. Using event-by-event hydrodynamic simulations, we make quantitative predictions for several observables: mean transverse momentum, anisotropic flow coefficients, and their fluctuations. Results are shown as a function of collision centrality.

We construct parameter sets of the relativistic mean-field model fitted to the recent constraints on the asymmetry energy $J$ and the slope parameter $L$ for pure neutron matter. We find cases of unphysical behavior, i.e., the appearance of negative pressures, for stiff parameter sets with low values of the effective mass ${m}^{*}/m$. In some cases the equation of state of pure neutron matter turns out to be outside the allowed band given by chiral effective field theory. The mass-radius relations of neutron stars for all acceptable parameter sets shows a maximum mass in excess of $2{M}_{\ensuremath{\bigodot}}$ being compatible with pulsar mass measurements. Given the constraints on the model in the low-density regime coming from chiral effective theory, we find that the radius of a $1.4{M}_{\ensuremath{\bigodot}}$ neutron star is nearly independent of the value of $L$. This is in contrast to some previous claims for a strong connection of the slope parameter with the radius of a neutron star. In fact, the mass-radius relation turns out to depend only on the isoscalar parameters of…

The precision of the current generation of space-based cosmic-ray experiments, such as AMS-02, PAMELA, CALET, and ISS-CREAM, is now reaching $\ensuremath{\approx}1$--3%, from energies of GeV/nucleon to multi-TeV/nucleon. These and future measurements of the isotopic composition and energy spectra of cosmic rays may reveal signatures of as-yet unknown phenomena in a wide range of topics, provided that the currently large uncertainties of 20--50% in many of the isotopic production cross sections can be reduced. This paper provides a systematic study of the reaction channels to produce particular isotopes and identifies the most important channels for reducing the present uncertainties. It provides a first road map for planning new measurement campaigns worldwide to reach the desired uncertainties.

Invariant differential yields of deuterons and antideuterons in $pp$ collisions at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV and the yields of tritons, $^{3}\mathrm{He}$ nuclei, and their antinuclei at $\sqrt{s}$ = 7 TeV have been measured with the ALICE detector at the CERN Large Hadron Collider. The measurements cover a wide transverse momentum (${p}_{\text{T}}$) range in the rapidity interval $|y|<0.5$, extending both the energy and the ${p}_{\text{T}}$ reach of previous measurements up to 3 GeV/$c$ for $A=2$ and 6 GeV/$c$ for $A=3$. The coalescence parameters of (anti)deuterons and $^{3}\overline{\text{He}}$ nuclei exhibit an increasing trend with ${p}_{\text{T}}$ and are found to be compatible with measurements in $pA$ collisions at low ${p}_{\text{T}}$ and lower energies. The integrated yields decrease by a factor of about 1000 for each increase of the mass number with one (anti)nucleon. Furthermore, the deuteron-to-proton ratio is reported as a function of the average charged particle multiplicity at different center-of-mass energies.

We critically compare thermodynamic and kinetic approaches that have been recently used to study relations between the spin polarization and fluid vorticity in systems consisting of spin-1/2 particles. The thermodynamic approach refers to general properties of global thermal equilibrium with a rigidlike rotation and demonstrates that the spin-polarization and thermal-vorticity tensors are equal. On the other hand, the kinetic approach uses the concept of the Wigner function and its semiclassical expansion. In most of the works done so far, the Wigner functions satisfy kinetic equations with a vanishing collision term. We show that this assumption restricts significantly the applicability of such frameworks and, in contrast to many claims found in the literature, does not allow for drawing any conclusions regarding the relation between the thermal-vorticity and spin-polarization tensors, except for the fact that the two should be constant in global equilibrium. We further show how the kinetic-theory equations including spin degrees of freedom can be used to formulate a hydrodynamic…

We carry out the study of finite nuclei, infinite nuclear matter, and neutron star properties with the newly developed relativistic force, the Institute of Physics Bhubaneswar-I (IOPB-I). Using this force, we calculate the binding energies, charge radii, and neutron-skin thickness for some selected nuclei. From the ground-state properties of superheavy nuclei ($Z=120$), it is noticed that considerable shell gaps appear at neutron numbers $N=172$, 184, and 198, manifesting the magicity at these numbers. The low-density behavior of the equation of state for pure neutron matter is compatible with other microscopic models. Along with the nuclear symmetry energy, its slope and curvature parameters at the saturation density are consistent with those extracted from various experimental data. We calculate the neutron star properties with the equation of state composed of nucleons and leptons in $\ensuremath{\beta}$-equilibrium, which are in good agreement with the x-ray observations by Steiner [Astrophys. J. 722, 33 (2010)] and N\"attil\"a [Astron. Astrophys. 591, A25 (2016)]. Based on the…

We have identified the most probable projectile-target combination by studying the fusion cross section, evaporation residue cross section, compound nucleus formation probability (${P}_{\mathrm{CN}}$), and survival probability (${P}_{\mathrm{Surv}}$) of different projectile target combinations to synthesize the superheavy element $Z=122$. The selected most probable projectile-target combinations to synthesize the superheavy element $Z=122$ are $\mathrm{Cr}+\mathrm{Cf}$, $\mathrm{Fe}+\mathrm{Cm}$, $\mathrm{Se}+\mathrm{Ra}$, and $\mathrm{As}+\mathrm{Ac}$. Superheavy nuclei may decay through the different decay modes such as spontaneous fission, ternary fission, and cluster decay. We have also studied the half-lives of spontaneous fission, ternary fission, and cluster decay of the predicted nuclei for $Z=122$ and compared with that of alpha decay. This enables us to study the competition between spontaneous fission, ternary fission, cluster decay, and alpha decay in the superheavy nuclei of $Z=122$. The comparision of half lives for different decay modes reveals that alpha decay is…

We construct a nuclear interaction in chiral effective field theory with explicit inclusion of the $\mathrm{\ensuremath{\Delta}}$-isobar $\mathrm{\ensuremath{\Delta}}(1232)$ degree of freedom at all orders up to next-to-next-to-leading order (NNLO). We use pion-nucleon ($\ensuremath{\pi}N$) low-energy constants (LECs) from a Roy-Steiner analysis of $\ensuremath{\pi}N$ scattering data, optimize the LECs in the contact potentials up to NNLO to reproduce low-energy nucleon-nucleon scattering phase shifts, and constrain the three-nucleon interaction at NNLO to reproduce the binding energy and point-proton radius of $^{4}\mathrm{He}$. For heavier nuclei we use the coupled-cluster method to compute binding energies, radii, and neutron skins. We find that radii and binding energies are much improved for interactions with explicit inclusion of $\mathrm{\ensuremath{\Delta}}(1232)$, while $\mathrm{\ensuremath{\Delta}}$-less interactions produce nuclei that are not bound with respect to breakup into $\ensuremath{\alpha}$ particles. The saturation of nuclear matter is significantly improved,…

Quantum Monte Carlo methods have recently been employed to study properties of nuclei and infinite matter using local chiral effective-field-theory interactions. In this work, we present a detailed description of the auxiliary field diffusion Monte Carlo algorithm for nuclei in combination with local chiral two- and three-nucleon interactions up to next-to-next-to-leading order. We show results for the binding energy, charge radius, charge form factor, and Coulomb sum rule in nuclei with $3\ensuremath{\le}A\ensuremath{\le}16$. Particular attention is devoted to the effect of different operator structures in the three-body force for different cutoffs. The outcomes suggest that local chiral interactions fit to few-body observables give a very good description of the ground-state properties of nuclei up to $^{16}\mathrm{O}$, with the exception of one fit for the softer cutoff which predicts overbinding in larger nuclei.

In a previous publication, we have presented a model for the photoproduction of $J/\ensuremath{\psi}$ vector mesons off protons, where the proton structure in the impact-parameter plane is described by an energy-dependent hot-spot profile. Here we extend this model to study the photonuclear production of $J/\ensuremath{\psi}$ vector mesons in coherent and incoherent interactions of heavy nuclei. We study two methods to extend the model to the nuclear case: using the standard Glauber-Gribov formalism and using geometric scaling to obtain the nuclear saturation scale. We find that the incoherent cross section changes sizably with the inclusion of subnucleonic hot spots and that this change is energy dependent. We propose to search for this behavior by measuring the ratio of the incoherent to coherent cross sections at different energies. We compare the results of our model to results from the Relativistic Heavy-Ion Collider (RHIC) and from run 1 at the Large Hadron Collider (LHC), finding satisfactory agreement. We also present predictions for the LHC at the new energies reached in…

We describe ultrarelativistic heavy ion collisions at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider with a hybrid model using the IP-Glasma model for the earliest stage and viscous hydrodynamics and microscopic transport for the later stages of the collision. We demonstrate that within this framework the bulk viscosity of the plasma plays an important role in describing the experimentally observed radial flow and azimuthal anisotropy simultaneously. We further investigate the dependence of observables on the temperature below which we employ the microscopic transport description.

Carbon burning is a critical phase for nucleosynthesis in massive stars. The conditions for igniting this burning stage, and the subsequent isotope composition of the resulting ashes, depend strongly on the reaction rate for $^{12}\mathrm{C}+^{12}\mathrm{C}$ fusion at very low energies. Results for the cross sections for this reaction are influenced by various backgrounds encountered in measurements at such energies. In this paper, we report on a new measurement of $^{12}\mathrm{C}+^{12}\mathrm{C}$ fusion cross sections where these backgrounds have been minimized. It is found that the astrophysical $S$ factor exhibits a maximum around ${E}_{\mathrm{cm}}=3.5--4.0$ MeV, which leads to a reduction of the previously predicted astrophysical reaction rate.

We computed a new set of static fission properties suited for $r$-process calculations. The potential energy surfaces and collective inertias of 3640 nuclei in the superheavy region are obtained from self-consistent mean-field calculations using the Barcelona-Catania-Paris-Madrid energy density functional. The fission path is computed as a function of the quadrupole moment by minimizing the potential energy and exploring octupole and hexadecapole deformations. The spontaneous fission lifetimes are evaluated employing different schemes for the collective inertias and vibrational energy corrections. This allows us to explore the sensitivity of the lifetimes to those quantities together with the collective ground-state energy along the superheavy landscape. We computed neutron-induced stellar reaction rates relevant for $r$-process nucleosynthesis using the Hauser-Feshbach statistical approach and study the impact of collective inertias. The competition between different reaction channels including neutron-induced rates, spontaneous fission, and $\ensuremath{\alpha}$ decay is discussed…

A neutron $\ensuremath{\beta}$-decay asymmetry measurement using polarized ultracold neutrons (UCN) determines the correlation between the spin of the neutron and the momentum of the decay electron. The authors extract the ratio of the weak axial-vector to vector couplings with reduced uncertainties. This new result from the first measurement of this asymmetry using UCN contributes a benchmark for lattice QCD calculations and the possibility for improved precision on the CKM matrix element ${V}_{u\phantom{\rule{0}{0ex}}d}$ from neutron $\ensuremath{\beta}$ decay.

The QCD equation of state at zero baryon chemical potential is the only element of the standard dynamical framework to describe heavy ion collisions that can be directly determined from first principles. Continuum extrapolated lattice QCD equations of state have been computed using 2+1 quark flavors (up/down and strange) as well as 2+1+1 flavors to investigate the effect of thermalized charm quarks on QCD thermodynamics. Lattice results have also indicated the presence of new strange resonances that not only contribute to the equation of state of QCD matter but also affect hadronic afterburners used to model the later stages of heavy ion collisions. We investigate how these new developments obtained from first principles calculations affect multiparticle correlations in heavy ion collisions. We compare the commonly used equation of state S95n-v1, which was constructed using what are now considered outdated lattice results and hadron states, to the current state-of-the-art lattice QCD equations of state with 2+1 and 2+1+1 flavors coupled to the most up-to-date hadronic resonances and…

A detailed study of multiparticle azimuthal correlations is presented using $pp$ data at $\sqrt{s}=5.02$ and 13 TeV, and $p$+Pb data at $\sqrt{{s}_{\mathrm{NN}}}=5.02$ TeV, recorded with the ATLAS detector at the CERN Large Hadron Collider. The azimuthal correlations are probed using four-particle cumulants ${c}_{n}{4}$ and flow coefficients ${v}_{n}{4}={(\ensuremath{-}{c}_{n}{4})}^{1/4}$ for $n=2$ and 3, with the goal of extracting long-range multiparticle azimuthal correlation signals and suppressing the short-range correlations. The values of ${c}_{n}{4}$ are obtained as a function of the average number of charged particles per event, $\ensuremath{\langle}{N}_{\mathrm{ch}}\ensuremath{\rangle}$, using the recently proposed two-subevent and three-subevent cumulant methods, and compared with results obtained with the standard cumulant method. The standard method is found to be strongly biased by short-range correlations, which originate mostly from jets with a positive contribution to ${c}_{n}{4}$. The three-subevent method, on the other hand, is found to be least sensitive to…

If the thermal evolution of the hot young neutron star in the supernova remnant HESS J1731-347 is driven by neutrino emission, it provides a stringent constraint on the coupling of light (mass $\ensuremath{\ll}10\phantom{\rule{0.28em}{0ex}}\mathrm{keV}$) axion-like particles to neutrons. Using Markov-Chain Monte Carlo we find that for the values of axion-neutron coupling ${g}_{ann}^{2}>7.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}$ (90% c.l.) the axion cooling from the bremsstrahlung reaction $n+n\ensuremath{\rightarrow}n+n+a$ is too rapid to account for the high observed surface temperature. This implies that the Pecci-Quinn scale or axion decay constant ${f}_{a}>6.7\ifmmode\times\else\texttimes\fi{}{10}^{7}\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$ for KSVZ axions and ${f}_{a}>1.7\ifmmode\times\else\texttimes\fi{}{10}^{9}\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$ for DFSZ axions. The high temperature of this neutron star also allows us to tighten constraints on the size of the nucleon pairing gaps.

In this paper, with restored isospin symmetry, we evaluated the neutrinoless double-$\ensuremath{\beta}$-decay nuclear matrix elements for $^{76}\mathrm{Ge}, ^{82}\mathrm{Se}, ^{130}\mathrm{Te}, ^{136}\mathrm{Xe}$, and $^{150}\mathrm{Nd}$ for both the light and heavy neutrino mass mechanisms using the deformed quasiparticle random-phase approximation approach with realistic forces. We give detailed decompositions of the nuclear matrix elements over different intermediate states and nucleon pairs, and discuss how these decompositions are affected by the model space truncations. Compared to the spherical calculations, our results show reductions from $30%$ to about $60%$ of the nuclear matrix elements for the calculated isotopes mainly due to the presence of the BCS overlap factor between the initial and final ground states. The comparison between different nucleon-nucleon (NN) forces with corresponding short-range correlations shows that the choice of the NN force gives roughly $20%$ deviations for the light exchange neutrino mechanism and much larger deviations for the heavy…

We show that the commonly used criterion for $\ensuremath{\beta}$ equilibrium in neutrino-transparent dense nuclear matter becomes invalid as temperatures rise above 1 MeV. Such temperatures are attained in neutron-star mergers. By numerically computing the relevant weak-interaction rates we find that the correct criterion for $\ensuremath{\beta}$ equilibrium requires an isospin chemical potential that can be as large as 10--20 MeV, depending on the temperature at which neutrinos become trapped.

The Gamow-Teller (GT) matrix element contributing to tritium $\ensuremath{\beta}$ decay is calculated with trinucleon wave functions obtained from hyperspherical-harmonics solutions of the Schr\"odinger equation with the chiral two- and three-nucleon interactions including $\mathrm{\ensuremath{\Delta}}$ intermediate states that have recently been constructed in configuration space. Predictions up to next-to-next-to-next-to-leading order (N3LO) in the chiral expansion of the axial current (with $\mathrm{\ensuremath{\Delta}}$'s) overestimate the empirical value by 1--4%. By exploiting the relation between the low-energy constant (LEC) in the contact three-nucleon interaction and two-body axial current, we provide new determinations of the LECs ${c}_{D}$ and ${c}_{E}$ that characterize this interaction by fitting the trinucleon binding energy and tritium GT matrix element. Some of the implications that the resulting models of three-nucleon interactions have on the spectra of light nuclei and the equation of state of neutron matter are briefly discussed. We also provide a partial…

The $\ensuremath{\alpha}$-decay half-lives of superheavy nuclei (SHN) with $Z\ensuremath{\ge}104$ are investigated by employing the effective liquid drop model (ELDM). By comparison between the calculated half-lives and the experimental ones, it is shown that the ELDM is a successful model to reproduce the experimental half-lives of SHN. Within the ELDM the $\ensuremath{\alpha}$-decay half-lives of $Z=118\text{--}120$ isotopes are predicted by inputting the $\ensuremath{\alpha}$-decay energy (${Q}_{\ensuremath{\alpha}}$) values extracted from the newest Weizs\"acker-Skyrme-4 (WS4) model, the finite-range droplet model (FRDM), the Kourra-Tachibaba-Uno-Yamada (KTUY) formula, and the Hartree-Fock-Bogoliubov mean field with the D1S Gogny force (GHFB). It is found that the shell effects at $N=178$ and 184 are evident by analyzing the ${Q}_{\ensuremath{\alpha}}$ values and half-lives versus the neutron number $N$. Because the WS4 ${Q}_{\ensuremath{\alpha}}$ values have the smallest rms deviation, the predicted $\ensuremath{\alpha}$-decay half-lives could be more accurate than the ones of…

A nonrelativistic quark coalescence model is formulated for polarized vector mesons and baryons of spin-1/2 octet and spin-3/2 decuplet. With the spin density matrix, one can compute in a uniform way the polarizations of vector mesons and baryons from those of quarks and antiquarks with explicit momentum dependence. The results are compared to those obtained from kinetic and statistical models for hadrons.

Ab initio calculations of the Gamow-Teller (GT) matrix elements in the $\ensuremath{\beta}$ decays of $^{6}\mathrm{He}$ and $^{10}\mathrm{C}$ and electron captures in $^{7}\mathrm{Be}$ are carried out using both variational and Green's function Monte Carlo wave functions obtained from the Argonne ${v}_{18}$ two-nucleon and Illinois-7 three-nucleon interactions, and axial many-body currents derived from either meson-exchange phenomenology or chiral effective field theory. The agreement with experimental data is excellent for the electron captures in $^{7}\mathrm{Be}$, while theory overestimates the $^{6}\mathrm{He}$ and $^{10}\mathrm{C}$ data by $\ensuremath{\sim}2%$ and \ensuremath{\sim}10%, respectively. We show that for these systems correlations in the nuclear wave functions are crucial to explaining the data, while many-body currents increase by \ensuremath{\sim}2--3% the one-body GT contributions.

We discuss the adequate treatment of the three- and four-body dynamics for the quark model picture of double-charm baryons and tetraquarks. We stress that the variational and Born-Oppenheimer approximations give energies very close to the exact ones, while the diquark approximation might be somewhat misleading. The Hall-Post inequalities also provide very useful lower bounds that exclude the possibility of stable tetraquarks for some mass ratios and some color wave functions.

The ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN density measured at the exit of the biological shield was $184(32) \mathrm{UCN}/{\mathrm{cm}}^{3}$, a fourfold increase from the highest previously reported. The polarized UCN density stored in an external chamber was measured to be $39(7) \mathrm{UCN}/{\mathrm{cm}}^{3}$, which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of…

We develop a new dynamical model for high-energy heavy-ion collisions in the beam energy region of the highest net-baryon densities on the basis of nonequilibrium microscopic transport model jam and macroscopic ($3+1$)-dimensional hydrodynamics by utilizing a dynamical initialization method. In this model, dynamical fluidization of a system is controlled by the source terms of the hydrodynamic fields. In addition, time-dependent core-corona separation of hot regions is implemented. We show that our new model describes multiplicities and mean transverse mass in heavy-ion collisions within a beam-energy region of $3<\sqrt{{s}_{NN}}<30$ GeV. Good agreement of the beam-energy dependence of the ${K}^{+}/{\ensuremath{\pi}}^{+}$ ratio is obtained, which is explained by the fact that a part of the system is not thermalized in our core-corona approach.

This paper presents a measurement of jet fragmentation functions in 0.49 ${\mathrm{nb}}^{\ensuremath{-}1}$ of Pb+Pb collisions and 25 ${\mathrm{pb}}^{\ensuremath{-}1}$ of $pp$ collisions at $\sqrt{{s}_{\mathit{\text{NN}}}}=5.02 \text{TeV}$ collected in 2015 with the ATLAS detector at the LHC. These measurements provide insight into the jet quenching process in the quark-gluon plasma created in the aftermath of ultrarelativistic collisions between two nuclei. The modifications to the jet fragmentation functions are quantified by dividing the measurements in Pb+Pb collisions by baseline measurements in $pp$ collisions. This ratio is studied as a function of the transverse momentum of the jet, the jet rapidity, and the centrality of the collision. In both collision systems, the jet fragmentation functions are measured for jets with transverse momentum between 126 and 398 $\text{GeV}$ and with an absolute value of jet rapidity less than 2.1. An enhancement of particles carrying a small fraction of the jet momentum is observed, which increases with centrality and with increasing jet…

We present the first ab initio calculations of neutrinoless double-$\ensuremath{\beta}$ decay matrix elements in $A=6\ensuremath{-}12$ nuclei using variational Monte Carlo wave functions obtained from the Argonne ${v}_{18}$ two-nucleon potential and Illinois-7 three-nucleon interaction. We study both light Majorana neutrino exchange and potentials arising from a large class of multi-TeV mechanisms of lepton-number violation. Our results provide benchmarks to be used in testing many-body methods that can be extended to the heavy nuclei of experimental interest. In light nuclei we also study the impact of two-body short-range correlations and the use of different forms for the transition operators, such as those corresponding to different orders in chiral effective theory.

We employ a variety of ab initio methods, including Faddeev-Yakubovsky equations, no-core configuration interaction approach, coupled-cluster theory, and in-medium similarity renormalization group, to perform a comprehensive analysis of the nucleon-deuteron elastic and breakup reactions and selected properties of light and medium-mass nuclei up to $^{48}\mathrm{Ca}$ using the recently constructed semilocal coordinate-space regularized chiral nucleon-nucleon potentials. We compare the results with those based on selected phenomenological and chiral EFT two-nucleon potentials, discuss the convergence pattern of the chiral expansion, and estimate the achievable theoretical accuracy at various chiral orders using an approach to quantify truncation errors of the chiral expansion without relying on cutoff variation. We also address the robustness of this method and explore alternative ways to estimate the theoretical uncertainty from the truncation of the chiral expansion.

We address a discrepancy between different computations of $\ensuremath{\eta}/s$ (shear viscosity over entropy density) of hadronic matter. Substantial deviations of this coefficient are found between transport approaches mainly based on resonance propagation with finite lifetime and other (semianalytical) approaches with energy-dependent cross sections, where interactions do not introduce a timescale. We provide an independent extraction of this coefficient by using the newly developed SMASH (Simulating Many Accelerated Strongly interacting Hadrons) transport code, which is an example of a mainly resonance-based approach. We compare the results from SMASH with numerical solutions of the Boltzmann equation for simple systems using the Chapman-Enskog expansion, as well as previous results in the literature. Our conclusion is that the hadron interaction via resonance formation/decay strongly affects the transport properties of the system, resulting in significant differences in $\ensuremath{\eta}/s$ with respect to other approaches where binary collisions dominate. We argue that the…