Future opportunities for a small-system scan at RHIC

by Prof. Jiang-yong Jia (SUNY STONY BROOK)

Tuesday 14 May 2019, 10:30 → 11:30 Asia/Shanghai

B105 (CHEP)

The observation of multi-particle azimuthal correlations in high-energy small-system collisions has led to intense debate on its physical origin between two competing theoretical scenarios: one based on initial-state intrinsic momentum anisotropy (ISM), the other based on final-state collective response to the collision geometry (FSM). To complement the previous scan of asymmetric collision systems (p+Au, d+Au and He+Au), we propose a scan of small symmetric collision systems at RHIC, such as C+C, O+O, Al+Al and Ar+Ar sNN‾‾‾‾√=0.2 TeV, to further disentangle contributions from these two scenarios. These symmetric small systems have the advantage of providing access to geometries driven by the average shape of the nuclear overlap, compared to fluctuation-dominant geometries in asymmetric systems. A transport model is employed to investigate the expected geometry response in the FSM scenario. Different trends of elliptic flow with increasing charge particle multiplicity are observed between symmetric and asymmetric systems, while triangular flow appears to show a similar behavior. Furthermore, a comparison of O+O collisions at sNN‾‾‾‾√=0.2 TeV and at sNN‾‾‾‾√=2.76−7 TeV, as proposed at the LHC, provides a unique opportunity to disentangle the collision geometry effects at nucleon level from those arising from subnucleon fluctuations.