Fluctuation probes of early-time correlations in nuclear collisions

Abstract

Correlation measurements imply that anisotropic flow in nuclear collisions includes an interesting triangular component along with the more familiar elliptic-flow contribution. Triangular flow has been attributed to eventwise fluctuations in the initial shape of the collision volume. The following two questions are asked. First, how do these shape fluctuations impact other event-by-event observables? Second, can fundamental information on the early time fluctuations be disentangled from the complex flow that results? Correlation and fluctuation observables are studied in a framework in which flux tubes in an early Glasma stage later produce hydrodynamic flow. The calculated collision-energy dependence of multiplicity and transverse momentum fluctuations is in good accord with data from 62.4 GeV Au $+$ Au up to 2.76 TeV Pb $+$ Pb.