Nuclear Theory·nucl-th
15 papers—9 primary·6 cross-listed
Marlene Nahrgang🇫🇷 · Marcus Bluhm🇵🇱 · Thomas Schäfer🇺🇸 · Steffen Bass🇺🇸
In this talk we present results obtained when fluid dynamical fluctuations are included in relativistic dimensional viscous fluid dynamics. We discuss effects of the interactions of fluctuations due to nonlinearities and the cutoff dependence.
Hui Li🇨🇳 · Hannah Petersen🇩🇪 · Long-Gang Pang🇺🇸 · Qun Wang🇨🇳 · Xiao-Liang Xia🇨🇳 · Xin-Nian Wang🇨🇳
We compute the fermion spin distribution in the vortical fluid created in off-central high-energy heavy-ion collisions. We employ the event-by-event (3+1)D viscous hydrodynamic model. The spin polarization density is proportional to the local fluid vorticity in quantum kinetic theory. As a result of strong collectivity, the spatial distribution of the local vorticity on the freeze-out hyper-surface strongly correlates to the rapidity and azimuthal angle distribution of fermion spins. We investigate the sensitivity of the local polarization to the initial fluid velocity in the hydrodynamic model and compute the global polarization of {\Lambda} hyperons by the AMPT model. The energy dependence of the global polarization agrees with the STAR data.
Hai-Qing Zhou🇨🇳 · Shin Nan Yang🇹🇼
We evaluate the corrections of the two-photon exchange (TPE) process on the transition form factors. The contributions of the TPE process to the are calculated in a hadronic model with the inclusion of only the elastic nucleon intermediate states, to estimate its effects on the multipoles at the peak. We find that TPE effects on is very small. and are also little affected at small . For , the TPE effects reach about near GeV, depending on the model, MAID or SAID, used to emulate the data. For , the TPE effects decrease rapidly with increasing while growing with increasing to reach with GeV at . Sizeable TPE corrections to and found here points to the need of including TPE effects in the multipole analysis in the region of high and small . The TPE corrections to and obtained in our hadronic calculation are compared with those obtained in a partonic calculation for moderate momentum transfer of GeV.
We investigate modifications of mass and decay width of in nuclear matter in a chiral symmetric way. The nucleon and are introduced by a parity doublet model, and nuclear matter is constructed by one-loop diagrams of the nucleon and . The decay width of is studied respecting chiral symmetry. Our calculations show that the partial width of is slightly broadened by a collisional broadening, and that of is drastically suppressed at density. As a result, the total decay width gets small at density. These modifications, especially the drastic narrowing of partial width of , together with the dropping of mass of provide experiments for observing the partial restoration of chiral symmetry in nuclear matter by means of resonance with useful information.
Wei Chen🇨🇳 · Shanshan Cao🇺🇸 · Tan Luo🇨🇳 · Long-Gang Pang🇺🇸 · Xin-Nian Wang🇨🇳
Coupled Linear Boltzmann Transport and hydrodynamics (CoLBT-hydro) is developed for co-current and event-by-event simulations of jet transport and jet-induced medium excitation (j.i.m.e.) in high-energy heavy-ion collisions. This is made possible by a GPU parallelized (3+1)D hydrodynamics that has a source term from the energy-momentum deposition by propagating jet shower partons and provides real time update of the bulk medium evolution for subsequent jet transport. Hadron spectra in -jet events of A+A collisions at RHIC and LHC are calculated for the first time that include hadrons from both the modified jet and j.i.m.e.. CoLBT-hydro describes well experimental data at RHIC on the suppression of leading hadrons due to parton energy loss. It also predicts the enhancement of soft hadrons from j.i.m.e. The onset of soft hadron enhancement occurs at a constant transverse momentum due to the thermal nature of soft hadrons from j.i.m.e. which also have a significantly broadened azimuthal distribution relative to the jet direction. Soft hadrons in the direction are, on the other hand, depleted due to a diffusion wake behind the jet.
In this proceeding, I review what we have learned, and what we will be able to learn, about low- physics from proton-nucleus () collisions at RHIC and the LHC, and how this complements future Electron-Ion Collider (EIC) measurements. EIC not only will provide us essential and complementary information about the gluon saturation to the knowledge that we have learned from collisions at RHIC and the LHC, it will also allow us to visualize the internal structure of protons and nuclei in a multi-dimensional fashion with unprecedented precision.
K. Fossez · J. Rotureau · N. Michel · W. Nazarewicz
The binding-energy pattern along the neutron-rich oxygen chain, governed by an interplay between shell effects and many-body correlations impacted by strong couplings to one- and two-neutron continuum, make these isotopes a unique testing ground for nuclear models. In this work, we investigate ground states and low-lying excited states of O using the complex-energy Gamow Shell Model and Density Matrix Renormalization Group method with a finite-range two-body interaction optimized to the bound states and resonances of O, assuming a core of O. Our results suggest that the ground-state of O has a threshold character, i.e., is very weakly bound or slightly unbound. We also predict narrow excited resonances in O and O. The inclusion of the large continuum space significantly impacts predicted binding energies of O. This implies that the careful treatment of neutron continuum is necessary prior to assessing the spectroscopic quality of effective interactions in this region.
K. A. Gridnev · V. B. Soubbotin · X. Viñas · M. Centelles
In this paper we review the semiclassical extended Thomas-Fermi theory for describing the ground-state properties of nuclei. The binding energies calculated in this approach do not contain shell effects and, in this sense, they are analogous to those obtained from the mass formula. We discuss some techniques for incorporating the shell effects which are missing in the semiclassical calculation, such as the so-called expectation value method and the Kohn-Sham scheme. We present numerical applications for effective zero-range Skyrme forces and finite-range Gogny forces.
B. Behera · X. Viñas · T. R. Routray · L. M. Robledo · M. Centelles · S. P. Pattnaik
Deformed and spherical even-even nuclei are studied using a finite range simple effective interaction within the Hartree-Fock-Bogoliubov mean field approach. Different parameter sets of the interaction, corresponding to different incompressibility, are constructed by varying the exponent gamma of the density in the traditional density-dependent term. Ten of the twelve parameters of these interactions are determined from properties of asymmetric nuclear matter and spin polarized pure neutron matter. The two remaining parameters are fitted to reproduce the experimental binding energies known in 620 even-even nuclei using several variants of the rotational energy correction. The rms deviations for the binding energy depend on the value of gamma and the way the rotational energy correction is treated but they can be as low as 1.56 MeV, a value competitive with other renowned effective interactions of Skyrme and Gogny type. Charge radii are compared to the experimental values of 313 even-even nuclei and the rms deviation is again comparable and even superior to the one of popular Skyrme and Gogny forces. Emphasis is given to the deformation properties predicted with these interactions by analyzing the Potential Energy Surfaces for several well deformed nuclei and the fission barriers of some nuclei. Comparison of the results with the experimental information, where available, as well as with the results of the Gogny D1S force shows satisfactory agreement.
Nora Brambilla🇩🇪 · Vladyslav Shtabovenko🇩🇪 · Jaume Tarrús Castellà🇩🇪 · Antonio Vairo🇩🇪
Van der Waals interactions between two neutral but polarizable systems at a separation much larger than the typical size of the systems are at the core of a broad sweep of contemporary problems in settings ranging from atomic, molecular and condensed matter physics to strong interactions and gravity. We reexamine the dispersive van der Waals interactions between two hydrogen atoms. The novelty of the analysis resides in the usage of nonrelativistic EFTs of QED. In this framework, the van der Waals potential acquires the meaning of a matching coefficient in an EFT suited to describe the low energy dynamics of an atom pair. It may be computed systematically as a series in times some typical atomic scale and in the fine structure constant . The van der Waals potential gets short range contributions and radiative corrections, which we compute in dimensional regularization and renormalize here for the first time. Results are given in spacetime dimensions. One can distinguish among different regimes depending on the relative size between and the typical atomic bound state energy . Each regime is characterized by a specific hierarchy of scales and a corresponding tower of EFTs. The short distance regime is characterized by and the LO van der Waals potential is the London potential. We compute also NNNLO corrections. In the long distance regime we have . In this regime, the van der Waals potential contains contact terms, which are parametrically larger than the Casimir-Polder potential that describes the potential at large distances. In the EFT the Casimir-Polder potential counts as a NNNLO effect. In the intermediate distance regime, , a significantly more complex potential is obtained which we compare with the two previous limiting cases. We conclude commenting on the hadronic van der Waals case.
Wei Li🇺🇸
I give an overview of the latest development in understanding collective phenomena in high-multiplicity hadronic final state from relativistic nucleus-nucleus, proton-nucleus and proton-proton collisions. Upon reviewing the experimental data and confronting them with theoretical models, a unified paradigm in describing the observed collectivity across all hadronic collision systems is emerging. Potential future paths toward addressing key open questions, especially on collectivity in small systems (pp, pA), are discussed.
J.W. Hwang🇰🇷 · S. Kim🇰🇷 · Y. Satou🇰🇷 · N.A. Orr🇫🇷 · Y. Kondo🇯🇵 · T. Nakamura🇯🇵 · J. Gibelin🇫🇷 · N.L. Achouri🇫🇷 · T. Aumann🇩🇪 · H. Baba🇯🇵 · F. Delaunay🇫🇷 · P. Doornenbal🇯🇵 and 33 other authors
The low-lying unbound level structure of the halo nucleus has been investigated using single-neutron knockout from on a carbon target at 280 MeV/nucleon. The invariant mass spectrum, derived from the momenta of the forward going beam velocity fragment and neutrons, was found to be dominated by a very narrow near threshold ( = 0.036(1) MeV) peak. Two less strongly populated resonance-like features were also observed at = 0.84(4) and 2.31(3) MeV, both of which exhibit characteristics consistent with neutron -shell hole states. Comparisons of the energies, measured cross sections and parallel momentum distributions to the results of shell-model and eikonal reaction calculations lead to spin-parity assignments of and for the levels at = 0.62(9) and 2.89(10) MeV with = 0.58(9) MeV. Spectroscopic factors were also deduced and found to be in reasonable accord with shell-model calculations. The valence neutron configuration of the ground state is thus seen to include, in addition to the known component, a significant contribution. The level scheme of , including significantly the cross-shell state, is well accounted for by the YSOX shell-model interaction developed from the monopole-based universal interaction.
Marcus Bluhm🇺🇸 · Jiaxun Hou🇺🇸 · Thomas Schaefer🇺🇸
We determine the shear viscosity of the ultracold Fermi gas at unitarity in the normal phase using hydrodynamic expansion data. The analysis is based on a generalized fluid dynamic framework which ensures a smooth transition between the fluid dynamic core of the cloud and the ballistic corona. We use expansion data taken by Joseph et al. and measurements of the equation of state by Ku et al. We find that the shear viscosity to particle density ratio just above the critical temperature is . We also obtain evidence that the shear viscosity to entropy density ratio has a minimum slightly above with .
We investigate the pseudoscalar (PS) meson ( and ) quasi-distribution amplitude (QDA), which is supposed to be an asymptotic analog to the meson distribution amplitude (DA) in the limit of the large longitudinal PS-meson momentum, i.e. , in the nonperturbative region. For this purpose, we employ the nonlocal chiral-quark model (NLChQM) in the light-front formalism with a minimal Fock-state for the mesons at the low-energy scale parameter of the model GeV. As a trial, we extract the transverse-momentum distribution amplitude (TMDA) from the light-front wave function within the model, and convert it to QDA with help of the virtuality-distribution amplitude. By doing that, we derive an analytical expression for the nonperturbative QDA with the current-quark mass correction up to . Numerically, we confirm that the obtained TMDA reproduces the experimental data for the photon-pion transition form factor at the low- qualitatively well. We also observe that the obtained QDA approaches to DA as increases, showing the symmetric and asymmetric curves with respect to for the pion and kaon, respectively, due to the current-quark mass difference . Assigning , the moments are computed, using the pion and kaon QDAs, and there appear only a few percent deviations in the moments for in comparison to the values calculated directly from DAs. It turns out that the higher moments are more sensitive to the change of , whereas the lower ones depend less on it.
Prithwish Tribedy (for the STAR Collaboration)🇺🇸
We present STAR measurements of the charge-dependent three-particle correlator and elliptic flow in U+U, Au+Au and p+Au collisions at RHIC. The difference measures charge separation across the reaction plane, a predicted signal of the Chiral Magnetic Effect (CME). Although charge separation has been observed, it has been argued that the measured separation can also be explained by elliptic flow related backgrounds. In order to separate the two effects, we perform measurements of the -correlator where background expectations differ from magnetic field driven effects. A differential measurement of with the relative pseudorapidity () between the first and second particles indicate that in peripheral A+A and p+A collisions are dominated by short-range correlations in . However, a relatively wider component of the correlation in tends to vanish the same way as projected magnetic field as predicted by MC-Glauber simulations.
first authorsco-authorsvia INSPIRE