Light-heavy-ion collisions: A window into pre-equilibrium QCD dynamics?

Abstract

Relativistic collisions of light on heavy ions (p + Au at √ s = 7.7 GeV, p + Au, d + Au,3 √ He + Au at √s = 62.4 GeV and 200 GeV and p + Pb,3He + Pb at s = 5.02 TeV) are simulated using “superSONIC”, a model that includes pre-equilibrium flow, viscous hydrodynamics and a hadronic cascade afterburner. Even though these systems have strong gradients and only consist of at most a few tens of charged particles per unit rapidity, one finds evidence that a hydrodynamic description applies to these systems. Based on these simulations, the presence of a triangular flow component in d + Aucollisions at √ s = 200 GeV is predicted to be similar in magnitude to that found in 3He + Au collisions. Furthermore, the v3(pT) ratio of 3He + Au to d + Au is found to be sensitive to the presence of pre-equilibrium flow. This would imply an experimentally accessible window into pre-equilibrium QCD dynamics using light-heavy-ion collisions.