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

Relativistic collisions of light on heavy ions (p + Au at √s=7.7 s = 7.7 GeV, p + Au , d + Au , ³ 3 He + Au at √s=62.4 s = 62.4 GeV and 200 GeV and p + Pb , ³ 3 He + Pb at √s=5.02 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 + Au collisions at √s=200 s = 200 GeV is predicted to be similar in magnitude to that found in ³ 3 He + Au collisions. Furthermore, the v₃(pT) v 3 ( p T ) ratio of ³ 3 He + 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.