Hybrid Color Glass Condensate and hydrodynamic description of the Relativistic Heavy Ion Collider small system scan

Abstract

Multi-particle correlation observables in the Relativistic Heavy Ion Collider small system scan are computed in a framework that contains both initial state momentum anisotropies from the Color Glass Condensate effective theory and final state hydrodynamic evolution. The initial state is computed using the IP-Glasma model and coupled to viscous relativistic hydrodynamic simulations, which are followed by microscopic hadronic transport. All parameters of the calculation were previously constrained using experimental data on Au+Au collisions at the same center of mass energy. We find that the qualitative features of the experimental data, such as the system and centrality dependence of the charged hadron momentum anisotropy, can only be reproduced when final state interactions are present. On the other hand, we also demonstrate that the details of the initial state are crucially important for the quantitative description of observables in the studied small systems, as neglecting the initial transverse flow profile or the initial shear stress tensor, which contain information on the momentum anisotropy from the Color Glass Condensate, has dramatic effects on the produced final state anisotropy. We further show that the initial state momentum anisotropy is correlated with the observed elliptic flow in all small systems, with the effect increasing with decreasing multiplicity. We identify the precise measurement of v2 in d+Au and Au+Au collisions at RHIC energy at the same multiplicity as a means to reveal effects of the initial state momentum anisotropy.

Bulk viscosity and cavitation in heavy ion collisions

“…The issue of cavitation is not mentioned in Refs. [19,24], though we have confirmed with the authors that for their specific geometry (e.g. p + A) most of the spacetime volume is in fact in the cavitation regime.…”

“…First focusing on the results as used in Refs. [19,24], the vast majority of the space-time volume has Π/P 0 < −1 and hence the entire volume will undergo cavitation. The issue of cavitation is not mentioned in Refs.…”

“…We also note that in this hybrid approach, the transition temperature between hydrodynamics and hadron cascade is set at 145 MeV, corresponding to a point where ζ/s is actually quite small. This parameterization has also been applied to hydrodynamic calculations for small collision systems [24] -which is very relevant to this paper as the interplay of pre-hydrodynamic physics and QGP properties becomes critical.…”

“…In the calculations with Param. II that include large bulk viscosities over a wide range of temperatures, the issue of cavitation is not discussed [19,24]. A focus of this paper is to explore the issue of cavitation in these various scenarios.…”

Accessing the gluonic structure of light nuclei at a future electron-ion collider

“…Besides the fundamental information on the gluonic structure of light nuclei at small x that exclusive vector meson production can provide, it also has applications for the phenomenology of high energy nucleus-nucleus collisions. To interpret deuteron-gold and helium-gold measurements at RHIC, it is important to have precise knowledge of the small-x geometry of light ions, which is an input for model calculations involving hydrodynamic simulations of QGP evolution (see [11] for a review and [13,[58][59][60][61] for more recent developments).…”