Elliptic flow of light nuclei

Abstract

Using the coalescence model based on nucleons from a blast-wave model with its parameters fitted to the measured proton transverse momentum spectrum and elliptic flow in heavy ion collisions at the Relativistic Heavy Ion Collider, we study the elliptic flows of light nuclei in these collisions. We find that to describe the measured elliptic flows of deuterons (anti-deuterons) and tritons (helium-3) requires that the emission source for nucleons of high transverse momentum is more elongated along the reaction plane than in the perpendicular direction. Our results thus suggest that the elliptic flows of light nuclei can be used to study the nucleon emission source in relativistic heavy ion collisions.

Spectra and flow of light nuclei in relativistic heavy ion collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

“…These previous studies [18,19] have revealed that the formation of light nuclei is very sensitive to the phasespace distributions of protons and neutrons at kinetic freeze-out, which are strongly influenced by the dynamical evolution of the QGP and the hadronic fireball. In the standard model of relativistic heavy ion collisions, the evolving system after thermalization is described by hydrodynamics for the QGP fluid followed by a hadron cascade simulations for the hadronic evolution [25][26][27][28][29][30][31].…”

“…In the statistical model, the yields of hadrons and light nuclei can be nicely described with a few parameters related to the chemical freeze-out conditions [10,11]. In the coalescence model, light nuclei are formed through the recombination of protons and neutrons with close positions and velocities on the kinetic freeze-out surface [12][13][14][15][16][17][18][19][20].…”

“…On the other hand, Refs. [18,19] showed that the spectra and elliptic flow of light nuclei could be described by the coalescence model using the phasespace distribution of nucleons generated from a modified blast-wave model. Besides the usual parameters, such as the fugacity ξ, the kinetic freeze-out temperature T K , the nucleon emission proper time τ 0 , the radial flow velocity β(r) and p T -dependent elliptic flow harmonic coefficient ε(p T ), etc., which are required to fit the spectra and elliptic flow of pions, kaons and protons, additional space-momentum correlations between protons and neutrons are required in this study to fit the elliptic flow of deuterons and helium-3.…”

“…We emphasize that the parameters in iEBE-VISHNU simulations have been fixed by the yields, spectra and flow harmonics of all charged hadrons in previous studies [36,38]. Compared with the modified blastwave model [18,19] that introduces a parametrized spacemomentum correlation of nucleons to describe the elliptic flow of light nuclei, such space-momentum correlations of emitted hadrons are naturally included in iEBE-VISHNU through the dynamically generated nucleon distribution function without additional free parameters [25]. This paper is organized as the following: Sec.…”

First, second, third and fourth flow harmonics of deuterons and protons in Au+Au reactions at 1.23 AGeV

“…In a simplified picture, the (explosive) expansion is driven by the initial pressure and therefore links the pressure to the finally observable transverse momentum spectra and its anisotropy in the observed hadrons [3][4][5][6]. During the last 20 years the study of flow has been refined and the transverse expansion is now studied in terms of a Fourier decomposition, see [7][8][9][10][11][12][13][14][15][16][17] for an overview of the experimental activities and see [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] for the corresponding theoretical investigations. These flow components, called v n , are the expansion coefficients of the Fourier-series of the transverse momentum distribution [18]:…”