The 50 most-cited articles in Physical Review C, 2019

We develop a macroscopic description of the space-time evolution of the energy-momentum tensor during the pre-equilibrium stage of a high-energy heavy-ion collision. Based on a weak coupling effective kinetic description of the microscopic equilibration process (\`a la ``bottom-up''), we calculate the nonequilibrium evolution of the local background energy-momentum tensor as well as the nonequilibrium linear response to transverse energy and momentum perturbations for realistic boost-invariant initial conditions for heavy-ion collisions. We demonstrate how this framework can be used on an event-by-event basis to propagate the energy-momentum tensor from far-from-equilibrium initial-state models to the time ${\ensuremath{\tau}}_{\text{hydro}}$ when the system is well described by relativistic viscous hydrodynamics. The subsequent hydrodynamic evolution becomes essentially independent of the hydrodynamic initialization time ${\ensuremath{\tau}}_{\text{hydro}}$ as long as ${\ensuremath{\tau}}_{\text{hydro}}$ is chosen in an appropriate range where both kinetic and hydrodynamic…

Comprehensive results on the production of unidentified charged particles, ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}, {\mathrm{K}}^{\ifmmode\pm\else\textpm\fi{}}, {\mathrm{K}}_{\mathrm{S}}^{0}, {\mathrm{K}}^{*}{(892)}^{0}, p, \overline{p}, \ensuremath{\phi}$(1020), $\mathrm{\ensuremath{\Lambda}}, \overline{\mathrm{\ensuremath{\Lambda}}}, {\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}}, {\overline{\mathrm{\ensuremath{\Xi}}}}^{+}, {\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}}$, and ${\overline{\mathrm{\ensuremath{\Omega}}}}^{+}$ hadrons in proton-proton ($pp$) collisions at $\sqrt{s}=7$ TeV at midrapidity ($|y|<0.5$) as a function of charged-particle multiplicity density are presented. In order to avoid autocorrelation biases, the actual transverse momentum (${p}_{\mathrm{T}}$) spectra of the particles under study and the event activity are measured in different rapidity windows. In the highest multiplicity class, the charged-particle density reaches about 3.5 times the value measured in inelastic collisions. While the yield of protons normalized to pions remains approximately…

Effective field theories (EFTs) organize the description of complex systems into an infinite sequence of decreasing importance. Predictions are made with a finite number of terms, which induces a truncation error that is often left unquantified. We formalize the notion of EFT convergence and propose a Bayesian truncation error model for predictions that are correlated across the independent variables, e.g., energy or scattering angle. Central to our approach are Gaussian processes that encode both the naturalness and correlation structure of EFT coefficients. Our use of Gaussian processes permits efficient and accurate assessment of credible intervals, allows EFT fits to easily include correlated theory errors, and provides analytic posteriors for physical EFT-related quantities such as the expansion parameter. We demonstrate that model-checking diagnostics---applied to the case of multiple curves---are powerful tools for EFT validation. As an example, we assess a set of nucleon-nucleon scattering observables in chiral EFT. In an effort to be self-contained, appendices include…

The hot and dense matter generated in heavy-ion collisions contains intricate vortical structure in which the local fluid vorticity can be very large. Such vorticity can polarize the spin of the produced particles. We study the event-by-event generation of the so-called thermal vorticity in Au+Au collisions at energy region $\sqrt{s}=7.7--200$ GeV and calculate its time evolution, spatial distribution, etc., in a multiphase transport model. We then compute the spin polarization of the $\mathrm{\ensuremath{\Lambda}}$ and $\overline{\mathrm{\ensuremath{\Lambda}}}$ hyperons as a function of $\sqrt{s}$, transverse momentum ${p}_{T}$, rapidity, and azimuthal angle. Furthermore, we study the harmonic flow of the spin, in a manner analogous to the harmonic flow of the particle number. The measurement of the spin harmonic flow may provide a way to probe the vortical structure in heavy-ion collisions. We also discuss the spin polarization of ${\mathrm{\ensuremath{\Xi}}}^{0}$ and ${\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}}$ hyperons, which may provide further information about the spin…

Several transport models have been employed in recent years to analyze heavy-flavor meson spectra in high-energy heavy-ion collisions. Heavy-quark transport coefficients extracted from these models with their default parameters vary, however, by up to a factor of 5 at high momenta. To investigate the origin of this large theoretical uncertainty, a systematic comparison of heavy-quark transport coefficients is carried out between various transport models. Within a common scheme devised for the nuclear modification factor of charm quarks in a brick medium of a quark-gluon plasma, the systematic uncertainty of the extracted drag coefficient among these models is shown to be reduced to a factor of 2, which can be viewed as the smallest intrinsic systematical error band achievable at present time. This indicates the importance of a realistic hydrodynamic evolution constrained by bulk hadron spectra and of heavy-quark hadronization for understanding the final heavy-flavor hadron spectra and extracting heavy-quark drag coefficient. The transverse transport coefficient is less constrained…

Nuclear $\ensuremath{\beta}$ decay is a key process to understand the origin of heavy elements in the universe, while the accuracy is far from satisfactory for the predictions of $\ensuremath{\beta}$-decay half-lives by nuclear models to date. In this work, we pave a novel way to accurately predict $\ensuremath{\beta}$-decay half-lives with the machine learning based on the Bayesian neural network, in which the known physics has been explicitly embedded, including the ones described by the Fermi theory of $\ensuremath{\beta}$ decay, and the dependence of half-lives on pairing correlations and decay energies. The other potential physics, which is not clear or even missing in nuclear models nowadays, will be learned by the Bayesian neural network. The results well reproduce the experimental data with a very high accuracy and further provide reasonable uncertainty evaluations in half-life predictions. These accurate predictions for half-lives with uncertainties are essential for the $r$-process simulations.

We report on the first femtoscopic measurement of baryon pairs, such as $p\ensuremath{-}p, p\ensuremath{-}\mathrm{\ensuremath{\Lambda}}$, and $\mathrm{\ensuremath{\Lambda}}\ensuremath{-}\mathrm{\ensuremath{\Lambda}}$, measured by ALICE at the Large Hadron Collider (LHC) in proton-proton collisions at $\sqrt{s}=7\phantom{\rule{0.28em}{0ex}}\mathrm{TeV}$. This study demonstrates the feasibility of such measurements in $pp$ collisions at ultrarelativistic energies. The femtoscopy method is employed to constrain the hyperon-nucleon and hyperon-hyperon interactions, which are still rather poorly understood. A new method to evaluate the influence of residual correlations induced by the decays of resonances and experimental impurities is hereby presented. The $p\ensuremath{-}p, p\ensuremath{-}\mathrm{\ensuremath{\Lambda}}$, and $\mathrm{\ensuremath{\Lambda}}\ensuremath{-}\mathrm{\ensuremath{\Lambda}}$ correlation functions were fitted simultaneously with the help of a new tool developed specifically for the femtoscopy analysis in small colliding systems: Correlation Analysis Tool using the…

We construct the QCD equation of state at finite chemical potentials including net baryon, electric charge, and strangeness, based on the conserved charge susceptibilities determined from lattice QCD simulations and the equation of state of the hadron resonance gas model. For the application to relativistic heavy-ion collisions we consider the situation of strangeness neutrality and matter with a fixed electric charge-to-baryon ratio, resembling that of heavy nuclei. The importance of finite electric charge and strangeness chemical potentials for particle production in heavy-ion collisions is demonstrated using hydrodynamic simulations.

The Majorana Collaboration is operating an array of high-purity Ge detectors to search for the neutrinoless double-$\ensuremath{\beta}$ decay of $^{76}\mathrm{Ge}$. The Majorana Demonstrator consists of 44.1 kg of Ge detectors (29.7 kg enriched to 88% in $^{76}\mathrm{Ge}$) split between two modules constructed from ultraclean materials. Both modules are contained in a low-background shield at the Sanford Underground Research Facility in Lead, South Dakota. We present updated results on the search for neutrinoless double-$\ensuremath{\beta}$ decay in $^{76}\mathrm{Ge}$ with $26.0\ifmmode\pm\else\textpm\fi{}0.5$ kg yr of enriched exposure. With the Demonstrator's energy resolution of 2.53 keV FWHM at ${Q}_{\ensuremath{\beta}\ensuremath{\beta}}$, which is the best among all neutrinoless double-$\ensuremath{\beta}$ decay experiments, we observe one event in the region of interest with 0.65 events expected from the estimated background, resulting in a lower limit on the $^{76}\mathrm{Ge}$ neutrinoless double-$\ensuremath{\beta}$ decay half-life of…

The deuteron yield in Pb+Pb collisions at √ s NN = 2.76 TeV is consistent with thermal production at a freeze out temperature of T = 155 MeV.The existence of deuterons with binding energy of 2.2 MeV at this temperature was described as "snowballs in hell" [P.Braun-Münzinger, B. Dönigus, and N. Löher, CERN Courier, August 2015].We provide a microscopic explanation of this phenomenon, utilizing relativistic hydrodynamics and switching to a hadronic afterburner at the above-mentioned temperature of T = 155 MeV.The measured deuteron p T spectra and coalescence parameter B 2 (p T ) are reproduced without free parameters, only by implementing experimentally known cross sections of deuteron reactions with hadrons, most importantly π d ↔ π np.

Background: There is significant current interest in knowing the value of the proton radius and also its proper definition. Purpose: Combine the disparate literatures of hydrogen spectroscopy and diverse modern parton distributions to show that the quantity $r_p^2\equiv -6 G_E'(0)$ is the relativistically proper definition that originates from the separate bodies of work. Methods: Use perturbation theory, light-front dynamics and elementary techniques to find relativistically correct definitions of the proton radius and charge density. Results: It is found that the very same proton radius is accessed by measurements of hydrogen spectroscopy and elastic lepton scattering. The derivation of the mean-square radius as a moment of a spherically symmetric three-dimensional density is shown to be incorrect. A relativistically-correct, two-dimensional charge density is related to the diverse modern literature of various parton distributions. Relativistically invariant moments thereof are derived in a new moment expansion, the RME.

The process at the heart of neutrinoless double-$\ensuremath{\beta}$ decay, $nn\ensuremath{\rightarrow}pp\phantom{\rule{0.16em}{0ex}}{e}^{\ensuremath{-}}{e}^{\ensuremath{-}}$ induced by a light Majorana neutrino, is investigated in pionless and chiral effective field theory. We show in various regularization schemes the need to introduce a short-range lepton-number-violating operator at leading order, confirming earlier findings. We demonstrate that such a short-range operator is only needed in spin-singlet $S$-wave transitions, while leading-order transitions involving higher partial waves depend solely on long-range currents. Calculations are extended to include next-to-leading-order corrections in perturbation theory, where to this order no additional undetermined parameters appear. We establish a connection based on chiral symmetry between neutrinoless double-$\ensuremath{\beta}$ decay and nuclear charge-independence breaking induced by electromagnetism. Data on the latter confirm the need for a leading-order short-range operator but do not allow for a full determination of the…

We report a new measurement of ${D}^{0}$-meson production at mid-rapidity $(|y|<1)$ in Au + Au collisions at $\sqrt{{s}_{\mathrm{NN}}}=200\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$ utilizing the heavy flavor tracker, a high resolution silicon detector at the STAR experiment. Invariant yields of ${D}^{0}$ mesons with transverse momentum ${p}_{T}\ensuremath{\lesssim}9\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}/c$ are reported in various centrality bins (0--10%, 10--20%, 20--40%, 40--60%, and 60--80%). Blast-wave thermal models are used to fit the ${D}^{0}$-meson ${p}_{T}$ spectra to study ${D}^{0}$ hadron kinetic freeze-out properties. The average radial flow velocity extracted from the fit is considerably smaller than that of light hadrons $(\ensuremath{\pi},\phantom{\rule{0.16em}{0ex}}K$, and $p)$, but comparable to that of hadrons containing multiple strange quarks $(\ensuremath{\phi},{\mathrm{\ensuremath{\Xi}}}^{\ensuremath{-}})$, indicating that ${D}^{0}$ mesons kinetically decouple from the system earlier than light hadrons. The calculated ${D}^{0}$ nuclear modification factors…

Ultrarelativistic quantum molecular dynamics phase-space coalescence calculations for the production of deuterons are compared with available data for various reactions from the Facility for Antiproton and Ion Research energy regime energy regime over the CERN Super Proton Synchrotron--Relativistic Heavy Ion Collider Beam Energy Scan region up to CERN Large Hadron Collider energies. It is found that the production process of deuterons, as reflected in their rapidity and transverse-momentum distributions in $p+p$, $p+A$, and $A+A$ collisions in the mentioned energy regime, are in good agreement with experimental data. We further explore the energy and centrality dependence of the $d$/$p$ and $\overline{d}/\overline{p}$ ratios and compare with thermal model results. Finally, we discuss antideuteron production for selected systems. Overall, a good description of the experimental data is observed. Most importantly this good description is based only on a single set of coalescence parameters that is independent of energy and system size and can also be applied for antideuterons.

Calculations are presented for the time evolution of $^{240}\mathrm{Pu}$ from the proximity of the outer saddle point until the fission fragments are well separated, using the time-dependent density functional theory extended to superfluid systems. We have tested three families of nuclear energy density functionals and found that all functionals exhibit a similar dynamics: The collective motion is highly dissipative and with little trace of inertial dynamics, due to the one-body dissipation mechanism alone. This finding justifies the validity of using the overdamped collective motion approach and to some extent the main assumptions in statistical models of fission. This conclusion is robust with respect to the nuclear energy density functional used. The configurations and interactions left out of the present theory framework only increase the role of the dissipative couplings. An unexpected finding is varying the pairing strength within a quite large range has only minor effects on the dynamics. We find notable differences in the excitation energy sharing between the fission…

We report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at $\sqrt{{s}_{\text{NN}}}=7.7$, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR experiment at the BNL Relativistic Heavy Ion Collider. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter ${B}_{2}$ are discussed. We find that the values of ${B}_{2}$ for antideuterons are systematically lower than those for deuterons, indicating that the correlation volume of antibaryons is larger than that of baryons at $\sqrt{{s}_{\text{NN}}}$ from 19.6 to 39 GeV. In addition, values of ${B}_{2}$ are found to vary with collision energy and show a broad minimum around $\sqrt{{s}_{\text{NN}}}=20--40$ GeV, which might imply a change of the equation of state of the medium in these collisions.

The system-size dependence of hadrochemistry at vanishing baryon density is considered within the canonical statistical model (CSM) with local exact conservation of three conserved charges, allowing for a possibility of strangeness undersaturation, i.e., ${\ensuremath{\gamma}}_{S}\ensuremath{\le}1$. Exact baryon number conservation is found to be even more important than that of strangeness in the canonical suppression picture at the CERN Large Hadron Collider, in contrast to intermediate and low collision energies. The model is applied to $p\text{\ensuremath{-}}p$, $p$-Pb, and Pb-Pb data of the ALICE Collaboration. A chemical equilibrium CSM with a fixed ${T}_{\mathrm{ch}}=155$ MeV describes the trends seen in most yield ratios. However, this ``vanilla'' version of CSM predicts an enhancement of the $\ensuremath{\phi}/\ensuremath{\pi}$ ratio at smaller multiplicities, in stark contrast to the suppression seen in the data. The data are described with a 15% relative accuracy level whence a multiplicity dependence of both the temperature and the strangeness saturation parameter…

The suppression factor for single inclusive jets in $\text{Pb}+\text{Pb}$ collisions at the Large Hadron Collider (LHC) has a weak dependence on the transverse momentum ${p}_{T}$ and remains almost the same at two colliding energies, $\sqrt{s}=2.76$ and 5.02 TeV, though the central rapidity density of bulk hadrons increases by about 20%. This phenomenon is investigated within the linear Boltzmann transport (LBT) model, which includes elastic and inelastic processes based on perturbative QCD for both jet shower and recoil medium partons as they propagate through a quark-gluon plasma (QGP). With the dynamic evolution of the QGP given by the $3+1\mathrm{D}$ CLVisc hydrodynamic model with event-by-event fully fluctuating initial conditions, single inclusive jet suppression in $\text{Pb}+\text{Pb}$ collisions from LBT agrees well with experimental data. The weak $\sqrt{s}$ and ${p}_{T}$ dependence of the jet suppression factor at LHC are found to result directly from the $\sqrt{s}$ dependence of the initial jet ${p}_{T}$ spectra and slow ${p}_{T}$ dependence of the jet energy loss.…

The dynamic linear response of a quantum system is critical for understanding both the structure and dynamics of strongly interacting quantum systems, including neutron scattering from materials, photon and electron scattering from atomic systems, and electron and neutrino scattering by nuclei. We present a general algorithm for universal quantum computers to calculate the dynamic linear response function with controlled errors and to obtain information about specific final states that can be directly compared to experimental observations.

Fission of atomic nuclei often produces mass asymmetric fragments. However, the origin of this asymmetry was believed to be different in actinides and in the sub-lead region [Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010)]. It has recently been argued that quantum shell effects stabilizing pear shapes of the fission fragments could explain the observed asymmetries in fission of actinides [Scamps and Simenel, Nature 564, 382 (2018)]. This interpretation is tested in the sub-lead region using microscopic mean-field calculations of fission based on the Hartree-Fock approach with BCS pairing correlations. The evolution of the number of protons and neutrons in asymmetric fragments of mercury isotope fissions is interpreted in terms of deformed shell gaps in the fragments. A new method is proposed to investigate the dominant shell effects in the prefragments at scission. We conclude that the mechanisms responsible for asymmetric fissions in the sub-lead region are the same as in the actinide region, which is a strong indication of their universality.

Background: Simulations by transport codes are indispensable for extracting valuable physical information from heavy-ion collisions. Pion observables such as the ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ yield ratio are expected to be sensitive to the symmetry energy at high densities.Purpose: To evaluate, understand, and reduce the uncertainties in transport-code results originating from different approximations in handling the production of $\mathrm{\ensuremath{\Delta}}$ resonances and pions.Methods: We compare ten transport codes under controlled conditions for a system confined in a box, with periodic boundary conditions, and initialized with nucleons at saturation density and at a temperature of 60 MeV. The reactions $NN\ensuremath{\leftrightarrow}N\mathrm{\ensuremath{\Delta}}$ and $\mathrm{\ensuremath{\Delta}}\ensuremath{\leftrightarrow}N\ensuremath{\pi}$ are implemented, but the Pauli blocking and the mean-field potential are deactivated in the present comparison. Thus, these are cascade calculations including pions and $\mathrm{\ensuremath{\Delta}}$…

Background: In recent years, there has been increasing interest in multinucleon transfer processes in low-energy deep inelastic (damped) collisions of heavy ions. Partly, it was provoked by a possibility of using them as a method of production of heavy neutron-enriched nuclei. Possible promising projectile-target combinations include nuclei deformed in the ground state (e.g., actinides). Mutual orientations of such nuclei in the entrance channel of a reaction may significantly influence the reaction dynamics.Purpose: The major aim of the work is to implement a possibility of modeling collisions of statically deformed heavy nuclei within a multidimensional dynamical model based on the Langevin equations. Another purpose of the paper is to study the influence of mutual orientations of statically deformed nuclei on their collision dynamics. Finally, production yields of heavy transuranium nuclei in collisions of actinides are examined.Method: An analysis has been performed within a multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations [Phys.…

We present calculations of nucleon-deuteron scattering as well as ground and low-lying excited states of light nuclei in the mass range $A=3--16$ up through next-to-next-to-leading order in chiral effective field theory using semilocal coordinate-space regularized two- and three-nucleon forces. It is shown that both of the low-energy constants entering the three-nucleon force at this order can be determined from the triton binding energy and the differential cross section minimum in elastic nucleon-deuteron scattering. From all considered nucleon-deuteron scattering observables, the strongest constraint on these low-energy constants emerges from the precisely measured cross section minimum at ${E}_{N}=70$ MeV. The inclusion of the three-nucleon force is found to improve the agreement with the data for most of the considered observables.

We describe here microscopic calculations performed on the dominant forbidden transitions in reactor antineutrino spectra above 4 MeV using the nuclear shell model. By taking into account Coulomb corrections in the most complete way, we calculate the shape factor with the highest fidelity and show strong deviations from allowed approximations and previously published results. Despite small differences in the ab initio electron cumulative spectra, large differences on the order of several percent are found in the antineutrino spectra. Based on the behavior of the numerically calculated shape factors we propose a parametrization of forbidden spectra. Using Monte Carlo techniques we derive an estimated spectral correction and uncertainty due to forbidden transitions. We establish the dominance and importance of forbidden transitions in both the reactor anomaly and spectral shoulder analysis with their respective uncertainties. Based on these results, we conclude that a correct treatment of forbidden transitions is indispensable in both the normalization anomaly and spectral shoulder.

Stars heavier than several times the mass of the Sun undergo a core-collapse event at the end of their lives. The dynamics of this process, which may lead to a supernova explosion, is mainly determined by the equation of state of dense matter, which also determines whether the collapse gives birth to a neutron star or a black hole. Whereas it is relatively well understood how the properties of neutron stars are affected by variations in the nuclear equation of state, the authors probe the rather unexplored effects of such variations on supernova dynamics and their neutrino signals. The authors demonstrate that the core collapse is mainly affected by changes in the nucleon effective masses which, within the Skyrme model employed, control the yet poorly constrained finite temperature dependence of the equation of state.

Relativistic hydrodynamic equations for particles with spin $\frac{1}{2}$ are used to determine the space-time evolution of the spin polarization in a boost-invariant and transversely homogeneous background. The hydrodynamic approach uses the forms of the energy-momentum and spin tensors based on the de Groot, van Leeuwen, and van Weert formalism. Our calculations illustrate how the formalism of hydrodynamics with spin can be used to determine physical observables related to the spin polarization and how the latter can be compared with the experimental data.

Valuable theoretical predictions of nuclear dipole excitations in the whole chart are of great interest for different nuclear applications, including, in particular, nuclear astrophysics. Here on the basis of experimental and theoretical information on the $E1$ and $M1$ strength functions, inspired both from axially deformed quasiparticle random-phase approximation and shell-model calculations, we derive simple expressions to determine systematically the dipole strength in order to update former prescriptions with a special emphasis on new expressions for the $M1$ spin-flip and scissors modes. We compare our final prediction of the $E1$ and $M1$ strengths with available experimental data at low energies and show that a relatively good agreement is obtained. Its impact on the total radiative width as well as radiative neutron capture cross sections is also discussed. The new expressions are believed to represent an improvement with respect to the analytical systematics proposed in the past and used traditionally in reaction codes, such as the recommended ripl-3 prescriptions.

We extend the parton-hadron string dynamics (PHSD) transport approach in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections as a function of temperature $T$ and baryon chemical potential ${\ensuremath{\mu}}_{B}$ on the basis of the effective propagators and couplings from the dynamical quasiparticle model (DQPM) that is matched to reproduce the equation of state of the partonic system above the deconfinement temperature ${T}_{c}$ from lattice QCD. We calculate the collisional widths for the partonic degrees of freedom at finite $T$ and ${\ensuremath{\mu}}_{B}$ in the timelike sector and conclude that the quasiparticle limit holds sufficiently well. Furthermore, the ratio of shear viscosity $\ensuremath{\eta}$ over entropy density $s$, i.e., $\ensuremath{\eta}/s$, is evaluated using the collisional widths and compared to lattice QCD calculations for ${\ensuremath{\mu}}_{B}=0$ as well. We find that the novel ratio $\ensuremath{\eta}/s$ does not differ very much from that calculated within the original DQPM on the basis of the…

We use a thermal model with single freeze-out to determine longitudinal polarization of $\mathrm{\ensuremath{\Lambda}}$ hyperons emitted from a hot and rotating hadronic medium. We consider the top RHIC energies and use the model parameters determined in the previous analyses of particle spectra and elliptic flow. Using a direct connection between the spin polarization tensor and thermal vorticity, we reproduce earlier results which indicate a quadrupole structure of the longitudinal component of the polarization three-vector with an opposite sign compared to that found in the experiment. We further use only the spatial components of the thermal vorticity in the laboratory system to define polarization and show that this leads to the correct sign and magnitude of the quadrupole structure. This procedure resembles a non-relativistic connection between the polarization three-vector and vorticity employed in other works. In general, our results bring further evidence that the spin polarization dynamics in heavy-ion collisions may be not directly related to the thermal vorticity. The…

The recent observation of spin polarization of $\mathrm{\ensuremath{\Lambda}}$ hyperons indicates the existence of a strong vorticity in heavy-ion collisions. However, experimental measurements and theoretical calculations of the azimuthal-angle dependence of the longitudinal and transverse spin polarization of $\mathrm{\ensuremath{\Lambda}}$ hyperons at mid-rapidity have opposite signs. The authors present a detailed study of the feed-down effect of higher-mass hyperons, but the discrepancy persists which challenges the connection between spin polarization and thermal vorticity.

We present a detailed comparison of coalescence and thermal-statistical models for the production of (anti-) (hyper-)nuclei in high-energy collisions. For the first time, such a study is carried out as a function of the size of the object relative to the size of the particle emitting source. Our study reveals large differences between the two scenarios for the production of objects with extended wave functions. While both models give similar predictions and show similar agreement with experimental data for (anti-)deuterons and (anti-)$^{3}\mathrm{He}$ nuclei, they largely differ in their description of (anti-)hypertriton production. We propose to address experimentally the comparison of the production models by measuring the coalescence parameter systematically for different (anti-)(hyper-)nuclei in different collision systems and differentially in multiplicity. Such measurements are feasible with the current and upgraded Large Hadron Collider experiments. Our findings highlight the unique potential of ultrarelativistic heavy-ion collisions as a laboratory to clarify the internal…

We apply the basis light front quantization (BLFQ) approach to describe the valence structures of the charged light meson ground states. Specifically, the light front wave functions of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}^{\ifmmode\pm\else\textpm\fi{}}$, and ${K}^{*\ifmmode\pm\else\textpm\fi{}}$ are obtained as the eigenvectors of the light front effective Hamiltonians with confinement potentials supplemented by the color singlet Nambu--Jona-Lasinio (NJL) interactions. We adjust our model such that the spectrum of these ground states and the charge radii of the pseudoscalar states agree with experimental results. We present the elastic form factors and parton distribution amplitudes (PDAs) as illustrations of the internal structures of the pseudoscalar pions and kaons in terms of valence quarks.

We present a general systematic formalism for describing dynamics of fluctuations in an arbitrary relativistic hydrodynamic flow, including their feedback (known as long-time hydrodynamic tails). The fluctuations are described by two-point equal-time correlation functions. We introduce a definition of equal time in a situation where the local rest frame is determined by the local flow velocity and a method of taking derivatives and Wigner transforms of such equal-time correlation functions, which we call confluent. We find that not only do the equations for confluent Wigner functions resemble kinetic equations but also the kinetic equation for phonons propagating on an arbitrary background nontrivially matches the equations for Wigner functions, including relativistic inertial and Coriolis forces due to acceleration and vorticity of the flow. We also describe the procedure of renormalization of short-distance singularities which eliminates cutoff dependence, allowing efficient numerical implementation of these equations.

We have obtained the Love number and corresponding tidal deformabilities $(\mathrm{\ensuremath{\Lambda}})$ associated with the relativistic mean-field parametrizations shown to be consistent (CRMF) with the nuclear matter, pure neutron matter, symmetry energy, and its derivatives [Dutra et al., Phys. Rev. C 90, 055203 (2014)]. Our results show that CRMF models present very good agreement with the recent data from binary neutron star merger event GW170817. They also confirm the strong correlation between ${\mathrm{\ensuremath{\Lambda}}}_{1.4}$ and the radius of canonical stars $({R}_{1.4})$. When a recent GW170817 constraint on ${\mathrm{\ensuremath{\Lambda}}}_{1.4}$ and the corresponding radius ${R}_{1.4}$ is used, the majority of the models tested are shown to satisfy it.

In recent years the understanding of the limits of the smallest possible droplet of the quark gluon plasma has been called into question. Experimental results from both the Large Hadron Collider and the Relativistic Heavy Ion Collider have provided hints that the quark gluon plasma may be produced in systems as small as that formed in $p\mathrm{Pb}$ or $d\mathrm{Au}$ collisions. Yet alternative explanations still exist from correlations arising from quarks and gluons in a color glass condensate picture. In order to resolve these two scenarios, a system-size scan has been proposed at the Large Hadron Collider for collisions of ArAr and OO. Here we make predictions for a possible future run of ArAr and OO collisions at the Large Hadron Collider and study the system-size dependence of a variety of flow observables. We find that linear response (from the initial conditions to the final flow harmonics) becomes more dominant in smaller systems, whereas the $\text{linear}+\text{cubic}$ response can accurately predict multiparticle cumulants for a wide range of centralities in large systems.

We introduce a new relativistic energy density functional constrained by the ground state properties of atomic nuclei along with the isoscalar giant monopole resonance energy and dipole polarizability in $^{208}\mathrm{Pb}$. A unified framework of the relativistic Hartree-Bogoliubov model and random phase approximation based on the relativistic density-dependent point coupling interaction is established in order to determine the DD-PCX parametrization by ${\ensuremath{\chi}}^{2}$ minimization. This procedure is supplemented with the covariance analysis in order to estimate statistical uncertainties in the model parameters and observables. The effective interaction DD-PCX accurately describes the nuclear ground state properties including the neutron-skin thickness, as well as the isoscalar giant monopole resonance excitation energies and dipole polarizabilities. The implementation of the experimental data on nuclear excitations allows constraining the symmetry energy close to the saturation density, and the incompressibility of nuclear matter by using genuine observables on finite…

Differences in the equation of state (EOS) of dense matter translate into differences in astrophysical simulations and their multimessenger signatures. Thus, extending the number of EOSs for astrophysical simulations allows us to probe the effect of different aspects of the EOS in astrophysical phenomena. In this work, we construct the EOS of hot and dense matter based on the Akmal, Pandharipande, and Ravenhall (APR) model and thereby extend the open-source SROEOS code which computes EOSs of hot dense matter for Skyrme-type parametrizations of the nuclear forces. Unlike Skrme-type models, in which parameters of the interaction are fit to reproduce the energy density of nuclear matter and/or properties of heavy nuclei, the EOS of APR is obtained from potentials resulting from fits to nucleon-nucleon scattering and properties of light nuclei. In addition, this EOS features a phase transition to a spin-isospin ordered state of nucleons, termed a neutral pion condensate, at supranuclear densities. We show that differences in the effective masses between EOSs have consequences for the…

This hyperon-nucleon paper is part of a simultaneous treatment of all baryon-baryon systems: $N\phantom{\rule{0}{0ex}}N$, $Y\phantom{\rule{0}{0ex}}N$, and $Y\phantom{\rule{0}{0ex}}Y$. Utilizing a meson-exchange potential approach, all $8\ifmmode\times\else\texttimes\fi{}8$ baryon-baryon channels are described in a model with SU(3)-symmetric couplings consistent with the constituent quark model. A high-quality fit is achieved for the $N\phantom{\rule{0}{0ex}}N$ data (${T}_{\text{Lab}}<350$ MeV) and the available $p$-$\mathrm{\ensuremath{\Lambda}}$ and $p$-$\mathrm{\ensuremath{\Sigma}}$ data.

We calculate the bulk-viscous dissipation time for adiabatic density oscillations in nuclear matter at densities of one to seven times the nuclear saturation density and at temperatures ranging from 1 MeV, where corrections to previous low-temperature calculations become important, up to 10 MeV, where the assumption of neutrino transparency is no longer valid. Under these conditions, which are expected to occur in neutron star mergers, damping of density oscillations arises from $\ensuremath{\beta}$ equilibration via weak interactions. We find that for 1-kHz oscillations the shortest dissipation times are in the 5- to 20-ms range, depending on the equation of state, which means that bulk viscous damping could affect the dynamics of a neutron star merger. For higher frequencies, the dissipation time can be even shorter.

The effect of pasta phases on the quark-hadron phase transition is investigated for a set of relativistic mean-field equations of state for both hadron and quark matter. The results of the full numerical solution with pasta phases are compared with those of an interpolating construction used in previous works, for which we demonstrate an adequate description of the numerical results. A one-to-one mapping of the free parameter of the construction to the physical surface tension of the quark-hadron interface is obtained for which a fit formula is given. For each pair of quark and hadron matter models the critical value of the surface tension is determined, above which the phase transition becomes close to the Maxwell construction. This result agrees well with earlier theoretical estimates. The study is extended to neutron star matter in beta equilibrium with electrons and muons and is applied to investigate the effect of pasta phases on the structure of hybrid compact stars and the robustness of a possible third family solution.

We exploit the many-body self-consistent Green's function method to analyze finite-temperature properties of infinite nuclear matter and to explore the behavior of the thermal index used to simulate thermal effects in equations of state for astrophysical applications. We show how the thermal index is both density and temperature dependent, unlike often considered, and we provide an error estimate based on our ab initio calculations. The inclusion of three-body forces is found to be critical for the density dependence of the thermal index. We also compare our results to a parametrization in terms of the density dependence of the nucleon effective mass. Our findings point to possible shortcomings of predictions made for the gravitational-wave signal from neutron-star merger simulations with a constant thermal index.

Background: Predicting the properties of neutron-rich nuclei far from the valley of stability is one of the major challenges of modern nuclear theory. In heavy and superheavy nuclei, a difference of only a few neutrons is sufficient to change the dominant fission mode. A theoretical approach capable of predicting such rapid transitions for neutron-rich systems would be a valuable tool to better understand $r$-process nucleosynthesis or the decay of superheavy elements.Purpose: In this work, we investigate for the first time the transition from asymmetric to symmetric fission through the calculation of primary fission yields with the time-dependent generator coordinate method (TDGCM). We choose here the transition in neutron-rich fermium isotopes, which was the first to be observed experimentally in the late 1970s and is often used as a benchmark for theoretical studies.Methods: We compute the primary fission fragment mass and charge yields for $^{254}\mathrm{Fm}, ^{256}\mathrm{Fm}$, and $^{258}\mathrm{Fm}$ from the TDGCM under the Gaussian overlap approximation. The static part of…

Background: Multinucleon transfer reactions at low-energy collisions are considered to be promising for the production of new exotic nuclei, which are difficult to produce by other methods. Theoretical studies are required to provide reliable predictions for the experiments and to help understand the microscopic mechanism in multinucleon transfer reactions.Purpose: We provide a predictive approach for production cross sections and show how and to what extent the microscopic approach works well in multinucleon transfer reactions.Methods: We employ the $\text{TDHF}\phantom{\rule{0.16em}{0ex}}+\phantom{\rule{0.16em}{0ex}}\text{GEMINI}$ approach, which combines the microscopic time-dependent Hartree-Fock (TDHF) model with the state-of-art statistical model $\text{GEMINI}\phantom{\rule{0.16em}{0ex}}++$, to take into account both the multinucleon transfer dynamics and the secondary de-excitation process. The properties of primary products in multinucleon transfer process, such as transfer probabilities and primary cross sections, are extracted from TDHF dynamics using the particle-number…

We calculate the gravitational form factors of the pion, $\ensuremath{\sigma}$ meson, and $\ensuremath{\rho}$ meson in the Nambu--Jona-Lasinio model of quantum chromodynamics. The canonical energy-momentum tensor (EMT) is used in their derivation, allowing the possibility of an antisymmetric contribution when the hadron has intrinsic spin. We show that the asymmetric graviton vertex arising from the canonical EMT satisfies a simpler Ward-Takahashi identity (WTI) than the symmetric graviton vertex of the Belinfante EMT. The necessity of fully dressing the graviton vertex through the relevant Bethe-Salpeter equation is demonstrated for observing both the WTI and a low-energy pion theorem. Lastly, we calculate static moments of the meson EMT decompositions, obtaining predictions for the meson mass radii. We find light cone mass radii of 0.27 fm for the pion, 0.32 fm for the $\ensuremath{\sigma}$, and 0.32 fm for the $\ensuremath{\rho}$. For the pion and $\ensuremath{\rho}$, these are smaller than the light cone charge radii, respectively 0.51 fm and 0.45 fm, while we have a…

We study multiparticle azimuthal correlations in relativistic heavy-ion collisions at a center-of-mass energy of 200 GeV. We use the impact parameter-dependent Glasma model to initialize the viscous hydrodynamic simulation MUSIC and employ the UrQMD transport model for the low-temperature region of the collisions. In addition, we study effects of local charge and global momentum conservation among the sampled particles. With the exception of the lowest-order three-particle correlator ${C}_{112}$, our framework provides a good description of the existing charge-inclusive azimuthal correlation data for Au+Au and U+U collisions at the Relativistic Heavy-Ion Collider (RHIC). We also present results for charge-dependent two- and three-particle correlators in Au+Au and U+U collisions and make predictions for isobar (Ru+Ru and Zr+Zr) collisions to provide a much-needed baseline for the search for the chiral magnetic effect at RHIC.

The factorization scheme, based on the impulse approximation and the spectral function formalism, has been recently generalized to allow the description of electromagnetic nuclear interactions driven by two-nucleon currents. We have extended this framework to the case of weakly charged and neutral currents, and carried out calculations of the double-differential neutrino-carbon and neutrino-oxygen cross sections using two different models of the target spectral functions. The results, showing a moderate dependence on the input spectral function, confirm that our approach provides a consistent treatment of all reaction mechanisms contributing to the signals detected by accelerator-based neutrino experiments.

We construct an equation of state for quantum chromodynamics (QCD) at finite temperature and chemical potentials for baryon number $B$, electric charge $Q$, and strangeness $S$. We use the Taylor expansion method to the fourth power for the chemical potentials. This requires the knowledge of all diagonal and nondiagonal $BQS$ correlators up to fourth order: These results recently became available from lattice QCD simulations, albeit only at a finite lattice spacing ${N}_{t}=12$. We smoothly merge these results to the hadron resonance gas as model, to be able to reach temperatures as low as 30 MeV; in the high-temperature regime, we impose a smooth approach to the Stefan-Boltzmann limit. We provide a parametrization for each one of these $BQS$ correlators as functions of the temperature. We then calculate pressure, energy density, entropy density, baryonic, strangeness, and electric charge densities and compare the two cases of strangeness neutrality and ${\ensuremath{\mu}}_{S}={\ensuremath{\mu}}_{Q}=0$. Finally, we calculate the isentropic trajectories and the speed of sound and…

We present an upgraded version of the SPY model, called SPY2 for version 2 of the scission point yield, to estimate mainly the yields and the kinetic energy distributions of fission fragments: The theoretical framework is similar to our previous version, i.e., a statistical scission point model, but this version is based on fully microscopic nuclear ingredients describing the fragments properties at the scission point. These include the static properties of some 7000 nuclei at 120 axial quadrupole deformations, such as binding energies, proton densities, single-particle level schemes, and states densities, coherently calculated within the constrained Hartree-Fock-Bogoliubov model on the basis of the Skyrme BSk27 interaction. The use of microscopic ingredients has been extended to the proton density distribution and the nuclear states densities. Considering realistic proton densities of fragments allows us to improve the definition of the scission point as well as the prediction of the kinetic energy distribution and to link the kinetic energy to the diffuseness of the fragments'…

The production of a hard dijet with small transverse momentum imbalance in semi-inclusive DIS probes the conventional and linearly polarized Weizs\"acker-Williams (WW) transverse momentum dependent (TMD) gluon distributions. The latter, in particular, gives rise to an azimuthal dependence of the dijet cross section. In this paper we analyze the feasibility of a measurement of these TMDs through dijet production in DIS on a nucleus at an electron-ion collider. We introduce the mcdijet Monte Carlo generator to sample quark-antiquark dijet configurations based on leading-order parton level cross sections with WW gluon distributions that solve the nonlinear small-$x$ QCD evolution equations. These configurations are fragmented to hadrons using PYTHIA, and final-state jets are reconstructed. We report on background studies and on the effect of kinematic cuts introduced to remove beam jet remnants. We estimate that with an integrated luminosity of 20 ${\mathrm{fb}}^{\ensuremath{-}1}/\mathrm{nucleon}$ one can determine the distribution of linearly polarized gluons with a statistical…

Mass measurements of fission and projectile fragments, produced via $^{238}\mathrm{U}$ and $^{124}\mathrm{Xe}$ primary beams, have been performed with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the Fragment Separator (FRS) Ion Catcher with a mass resolving power (FWHM) of up to 410 000 and an uncertainty of down to $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$. The nuclides were produced and separated in flight with the fragment separator FRS at 300 to 1000 MeV/u and thermalized in a cryogenic stopping cell. The data-analysis procedure was developed to determine with highest accuracy the mass values and the corresponding uncertainties for the most challenging conditions: down to a few events in a spectrum and overlapping distributions, which can be distinguished from a single peak only by a broader peak shape. With this procedure, the resolution of low-lying isomers is increased by a factor of up to 3 compared to standard data analysis. The ground-state masses of 31 short-lived nuclides of 15 different elements with half-lives of down to…