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Nuclear Theory·nucl-th

Monday·April 3, 2017

8 papers—5 primary·3 cross-listed

All8Primary5Cross-lists3
  1. 01

    Onset of hydrodynamics for a quark-gluon plasma from the evolution of moments of distribution functions

    Jean-Paul Blaizot🇫🇷 · Li Yan🇫🇷

    The pre-equilibrium evolution of a quark-gluon plasma produced in a heavy-ion collision is studied in the framework of kinetic theory. We discuss the approach to local thermal equilibrium, and the onset of hydrodynamics, in terms of a particular set of moments of the distribution function. These moments quantify the momentum anisotropies to a finer degree than the commonly used ratio of longitudinal to transverse pressures. They are found to be in direct correspondence with viscous corrections of hydrodynamics, and provide therefore an alternative measure of these corrections in terms of the distortion of the momentum distribution. As an application, we study the evolution of these moments by solving the Boltzmann equation for a boost invariant expanding system, first analytically in the relaxation time approximation, and then numerically for a quark-gluon plasma within the small angle approximation to the collision kernel.

    nucl-thhep-phnucl-exJHEP(2017)·54 citations
  2. 02

    Structure of the Roper Resonance from Lattice QCD Constraints

    Jia-jun Wu🇦🇺 · Derek B. Leinweber🇦🇺 · Zhan-wei Liu🇦🇺 · Anthony W. Thomas🇦🇺

    Two different descriptions of the existing pion-nucleon scattering data in the region of the Roper resonance are constructed. Both descriptions fit the experimental data very well. In one scenario the resonance is the result of strong rescattering between coupled meson-baryon channels, while in the other scenario, the resonance has a large bare-baryon (or quark-model like) component. The predictions of these two scenarios are compared with the latest lattice QCD simulation results in this channel. Consideration of the finite volume spectra, the manner in which the states are excited from the vacuum in lattice QCD and the composition of the states in Hamiltonian effective field theory enable a discrimination of these two different descriptions. We find the second scenario is not consistent with lattice QCD results whereas the first agrees with the lattice QCD constraints. In this scenario, the mass of the quark-model like state is approximately 2 GeV and in the finite volume of the lattice is dressed to place the first radial excitation of the nucleon at 1.9 GeV. Within this description, the infinite-volume Roper resonance is best described as a resonance generated dynamically through strongly coupled meson-baryon channels.

    nucl-thhep-lathep-phPRD(2018)·74 citations
  3. 03

    Reaction cross sections of proton scattering from carbon isotopes (A=8-22) by means of the relativistic impulse approximation

    Kaori Kaki

    Reaction cross sections of carbon isotopes for proton scattering are calculated in large energy region. Density distributions of carbon isotopes are obtained from relativistic mean field results. Calculations are based on two procedures: the Glauber theory and relativistic impulse approximation, and results are compared with each other as well as with experimental data. A strong relationship between reaction cross section and root-mean-square radius is clearly shown for 12C using a model distribution.

    nucl-thPTEP(2017)·10 citations
  4. 04

    Collective flow in 2.76 A TeV and 5.02 A TeV Pb+Pb collisions

    Wenbin Zhao🇨🇳 · Hao-jie Xu🇨🇳 · Huichao Song (Peking U.)🇨🇳

    In this paper, we study and predict flow observables in 2.76 A TeV and 5.02 A TeV Pb +Pb collisions, using the iEBE-VISHNU hybrid model with TRENto and AMPT initial conditions and with different forms of the QGP transport coefficients. With properly chosen and tuned parameter sets, our model calculations can nicely describe various flow observables in 2.76 A TeV Pb +Pb collisions, as well as the measured flow harmonics of all charged hadrons in 5.02 A TeV Pb +Pb collisions. We also predict other flow observables, including of identified particles, event-by-event distributions, event-plane correlations, (Normalized) Symmetric Cumulants, non-linear response coefficients and -dependent factorization ratios, in 5.02 A TeV Pb+Pb collisions. We find many of these observables remain approximately the same values as the ones in 2.76 A TeV Pb+Pb collisions. Our theoretical studies and predictions could shed light to the experimental investigations in the near future.

    nucl-thhep-phnucl-exEPJC(2017)·126 citations
  5. 05

    Anisotropic fluid dynamics for Gubser flow

    M. Martinez🇺🇸 · M. McNelis🇺🇸 · U. Heinz🇺🇸

    Exploring a variety of closing schemes to the infinite hierarchy of momentum moments of the exactly solvable Boltzmann equation for systems undergoing Gubser flow, we study the precision with which the resulting hydrodynamic equations reproduce the exact evolution of hydrodynamic moments of the distribution function. We find that anisotropic hydrodynamics, obtained by ex- panding the distribution function around a dynamically evolving locally anisotropic background whose evolution is matched to exactly reproduce the macroscopic pressure anisotropy caused by the different longitudinal and transverse expansion rates in Gubser flow, provides the most accurate macroscopic description of the microscopic kinetic evolution. This confirms a similar earlier finding for Bjorken flow [Molnár, Niemi and Rischke, Phys. Rev. D 94, 125003 (2016)]. We explain the physics behind this optimal matching procedure and show that one can efficiently correct for a non- optimized matching choice by adding a residual shear stress to the energy-momentum tensor whose evolution is again determined by the Boltzmann equation. Additional insights to guide the optimal choice of a macroscopic anisotropic hydrodynamic framework for strongly-coupled systems that do not admit a microscopic kinetic description are reported.

    nucl-thhep-phPRC(2017)·48 citations

Affiliations

first authorsco-authorsvia INSPIRE