Nuclear Theory·nucl-th

Wednesday·July 18, 2018

24 papers—12 primary·12 cross-listed

01
[Submitted on 16 Jul 2018]
Fluid dynamics of out of equilibrium boost invariant plasmas
Jean-Paul Blaizot🇫🇷 · Li Yan🇨🇦
We establish a set of equations for moments of the distribution function. In the relaxation time approximations, these moments obey a coupled set of equations that can be truncated order-by-order. Solving the equations of moments, we are able to identify an attractor solution that controls a transition from a free streaming fixed point to a hydrodynamic fixed point. In particular, this attractor solution provides a renormalization of the effective value of the shear viscosity to entropy density ratio, $η / s$ , taking into account off-equilibrium effects.
Comments:
2 figures and 4 pages; Proceedings of the 27th international conference on ultra-relativistic nucleus-nucleus collisions (Quark Matter 2018)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1807.06104 [pdf]
NPA(2019)·1 citation
02
[Submitted on 17 Jul 2018]
Collective effects in nuclear collisions: theory overview
Jorge Noronha (Sao Paulo U.)🇧🇷
In these proceedings I review recent developments concerning the hydrodynamic description of the quark-gluon plasma (QGP). I report on the progress towards more realistic simulations and discuss new features about the QGP transport coefficients of the hot (and baryon dense) medium formed in heavy ion collisions. A brief discussion is included on the applicability of hydrodynamics and its extension to the far-from-equilibrium regime.
Comments:
7 pages, 3 figures, invited plenary talk at the 27th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2018), Venice, Italy, 13-19 May 2018
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1807.06191 [pdf]
NPA(2019)·7 citations
03
[Submitted on 17 Jul 2018]
Z+jet productions in heavy-ion collisions
Shan-Liang Zhang🇨🇳 · Tan Luo🇨🇳 · Xin-Nian Wang🇨🇳 · Ben-Wei Zhang🇨🇳
We report a systematic study of Z+jet correlation in Pb+Pb collisions at the LHC by combining the next-leading-order matrix elements calculations with matched parton shower in Sherpa for the initial Z+jet production, and Linear Boltzmann transport Model for jet propagation in the expanding quark-gluon-plasma. Our numerical results can well explain CMS measurements on Z+jet correlation in Pb+Pb collisions: the shift of $p_{T}$ imbalance $x_{j Z} = p_{T}^{j e t} / p_{T}^{Z}$ and their mean values, the suppression of the average number of jet partners per Z boson $R_{j Z}$ , as well as the modification of azimuthal angle correlations $Δ ϕ_{j Z}$ . We also demonstrate that high-order corrections play a significant role in the understanding of Z+jet correlations at high energies.
Comments:
4 pages, 4 figures, talk at Quark Matter 2018 conference
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1807.06197 [pdf]
NPA(2019)·3 citations
04
[Submitted on 17 Jul 2018]
Quarkonium production in heavy ion collisions: coupled Boltzmann transport equations
Xiaojun Yao🇺🇸 · Weiyao Ke🇺🇸 · Yingru Xu🇺🇸 · Steffen Bass🇺🇸 · Berndt Müller🇺🇸
We develop a set of coupled Boltzmann equations to describe the dynamical evolution of heavy quarks and quarkonia inside the quark-gluon plasma. The quarkonium dissociation and recombination terms are calculated from pNRQCD. Their interplay drives the system to a detailed balance. The heavy quark energy loss term is necessary for the system to reach kinematic thermalization. By coupling the transport equations with initial particles' momenta generated by PYTHIA and hydrodynamic medium evolutions, we can describe the $R_{AA}$ of $Υ$ family at both RHIC and LHC energies. The transverse momentum azimuthal anisotropy of $Υ$ (1S) in $2.76$ TeV peripheral Pb-Pb collisions is also studied.
Comments:
4 pages, 3 figures, conference proceeding of Quark Matter 2018
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1807.06199 [pdf]
NPA(2019)·22 citations
05
[Submitted on 17 Jul 2018]
Rapidity decorrelation from hydrodynamic fluctuations
Azumi Sakai🇯🇵 · Koichi Murase🇯🇵 · Tetsufumi Hirano🇯🇵
We discuss rapidity decorrelation caused by hydrodynamic fluctuations in high-energy nuclear collisions at the LHC energy. We employ an integrated dynamical model which is a combination of the Monte Carlo version of Glauber model with extension to longitudinal direction for initial conditions, full three-dimensional relativistic fluctuating hydrodynamics for the space-time evolution of created matter in the intermediate stage and a hadronic cascade model in the late stage. We switch on and off the hydrodynamic fluctuations in the hydrodynamic stage to understand the effects of hydrodynamic fluctuations on factorisation ratios $r_{n} (η_{p}^{a}, η_{p}^{b})$ . To understand the rapidity gap dependence of the factorisation ratio comprehensively, we analyse Legendre coefficients $A_{2}^{k}$ and $B_{2}^{k}$ .
Comments:
4 pages, 3 figures, XXVIIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2018)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1807.06254 [pdf]
NPA(2019)·9 citations
06
[Submitted on 17 Jul 2018]
Hydrodynamic response in simulations within a multiphase transport model
De-Xian Wei🇨🇳 · Xu-Guang Huang🇨🇳 · Li Yan🇨🇦
We carry out simulations using a multiphase transport (AMPT) model to describe the observed flow signatures in $s_{N N} = 2.76$ TeV Pb-Pb collisions. Especially, we calculate the flow fluctuations of $v_{2}$ in terms of cumulant ratios and the standardized skewness. Based on event-by-event AMPT simulations, we study the linear and cubic response relation between $v_{2}$ and $ε_{2}$ . We found that the observed response relation is compatible to what has been noticed in hydrodynamic modelings, with similar dependence on shear viscosity. Besides, this response relation is not sensitive to nonflow effects.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1807.06299 [pdf]
PRC(2018)·18 citations
07
[Submitted on 17 Jul 2018]
Nonlinear coupling of flow harmonics in heavy-ion collisions
Giuliano Giacalone🇫🇷
Anisotropic flow coefficients beyond triangular flow receive important contributions from lower-order harmonics through nonlinear coupling. We present a theoretical framework which allows one to quantify the contribution induced by such nonlinear couplings to any flow harmonic of any order. We show the effectiveness of this formalism through an application to hexagonal flow, $V_{6}$ . We study, in particular, the coupling of $V_{6}$ to triangular flow, $V_{3}$ , in Pb+Pb collisions at $s = 2.76$ TeV, using both Large Hadron Collider data and event-by-event hydrodynamic calculations.
Comments:
4 pages; 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1807.06382 [pdf]
NPA(2019)·1 citation
08
[Submitted on 17 Jul 2018]
Nature of isoscalar dipole resonances in heavy nuclei
V.I. Abrosimov🇺🇦 · O.I. Davidovskaya🇺🇦
Isoscalar dipole nuclear response reveals the low- and high-energy resonances. The nature of isoscalar dipole resonances in heavy spherical nuclei is studied by using the translation-invariant kinetic model of small oscillations of finite Fermi systems. Calculations of the velocity field at the centroid energy show a pure vortex character of the low-energy isoscalar dipole resonance in spherical nuclei and confirm the anisotropic compression character of the high-energy one. The evolution of the velocity field in dependence on the excitation energy of the nucleus within the resonance width is studied. It is found that the low-energy isoscalar dipole resonance retains a vortex character while with increasing energy this collective excitation also involves compression. The high-energy resonance keeps the compression character with a change in the excitation energy within the resonance width but the compression-expansion region of the velocity field related to this resonance shifts inside the nucleus.
Comments:
9 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1807.06407 [pdf]
Ukr.J.Phys.(2018)·2 citations
09
[Submitted on 14 Jul 2018]
Neutron star matter with strange interactions in a relativistic quark model
H. S. Sahoo🇮🇳 · R. N. Mishra🇮🇳 · D. K. Mohanty🇮🇳 · P. K. Panda🇮🇳 · N. Barik🇺🇸
The effect of strange interactions in neutron star matter and the role of the strange meson-hyperon couplings are studied in a relativistic quark model where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to $σ$ , $ω$ , $ρ$ , $σ^{*}$ and $ϕ$ mesons through mean-field approximations. The meson-baryon couplings are fixed through the SU(6) spin-flavor symmetry and the SU(3) flavor symmetry to determine the hadronic equation of state (EoS). We find that the SU(3) coupling set gives the potential depth between $Λ$ s around $- 5$ MeV and favours a stiffer EoS.The radius for the canonical neutron star lies within a range of $12.7$ to $13.1$ km.
Comments:
9 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1609.02708, arXiv:1702.02310
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1807.06453 [pdf]
PRC(2018)·37 citations
10
[Submitted on 17 Jul 2018]
Statistical Properties of 56-57Fe with Multi-Shell Degrees of Freedom
Bassam Shehadeh🇸🇦 · James P. Vary🇺🇸
We investigate the statistical properties of 56-57Fe within a model capable of treating all the nucleons as active in an infinite model space including pairing effects. Working within the canonical ensemble, our model is built on single-particle states, thus it includes shell and subshell closures. We include spin correlation parameters to account for nucleon spin multiplicities. Pairing and shell effects are important in the low-temperature region where the quantum effects dominate. The validity of the model is extended to higher temperatures, approaching the classical regime, by including continuum states. We present results for excitation energy, heat capacity and level density of 56-57Fe. The resulting favorable comparisons with experimental data and with other approaches, where applicable, indicate that the methods we develop are useful for statistical properties of medium to heavy nuclei.
Comments:
26 pages and 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1807.06520 [pdf]
0 citations
11
[Submitted on 17 Jul 2018]
Measuring the Rate of Isotropization of Quark-Gluon Plasma Using Rapidity Correlations
George Moschelli🇺🇸 · Sean Gavin🇺🇸
We propose that rapidity dependent momentum correlations can be used to extract the shear relaxation time $τ_{π}$ of the medium formed in high energy nuclear collisions. The stress-energy tensor in an equilibrium quark-gluon plasma is isotropic, but in nuclear collisions it is likely very far from this state. The relaxation time $τ_{π}$ characterizes the rate of isotropization and is a transport coefficient as fundamental as the shear viscosity. We show that fluctuations emerging from the initial anisotropy survive to freeze-out, in excess of thermal fluctuations, influencing rapidity correlation patterns. We show that these correlations can be used to extract $τ_{π}$ . We describe a method for calculating the rapidity dependence of two-particle momentum correlations with a second order, causal, diffusion equation that includes Langevin noise as a source of thermal fluctuations. The causality requirement introduces the relaxation time and we link the shape of the rapidity correlation pattern to its presence. Here we examine how different equations of state and temperature dependent transport coefficients in the presence of realistic hydrodynamic flow influence the estimate of $τ_{π}$ . In comparison to RHIC data, we find that the ratio $τ_{π} / ν \approx 5 - 6$ where $ν = η / s T$ is the kinematic viscosity.
Comments:
Proceedings of The 27th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions, Venezia, Italy 13-19 May 2018
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1807.06532 [pdf]
NPA(2019)·4 citations
12
[Submitted on 17 Jul 2018]
Jet modification with medium recoil in quark-gluon plasma
Chanwook Park🇨🇦 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
Jet energy transported to quark-gluon plasma during jet-medium interaction excites the QGP medium and creates energetic thermal partons -- recoil particles or recoils. Modification of the jet structure in heavy ion collisions is studied using \textsc{martini}, in which recoil simulation is enabled. In large systems such as central Pb-Pb collisions, the recoil effect is expected to be critical due to strong jet-medium interaction. We show the results of the jet mass function and jet shape function are improved when the recoil particles are included in the reconstructed jets. We conclude that the energy carried by the recoil particles are regarded as a part of reconstructed jets and are necessary in studying jet modification in heavy ion collisions.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1807.06550 [pdf]
NPA(2019)·52 citations

Affiliations

first authorsco-authorsvia INSPIRE