Fluctuation Probes of Early-Time Correlations in Nuclear Collisions

TL;DR

This paper investigates how early-time shape fluctuations in nuclear collisions influence flow and other observables, using a flux tube model that aligns well with experimental data across various energies.

Contribution

It introduces a framework linking initial shape fluctuations to flow and fluctuation observables, providing a unified explanation consistent with experimental results.

Findings

Flux tube model reproduces multiplicity fluctuations.

Transverse momentum fluctuations match experimental data.

Early shape fluctuations impact flow and other observables.

Abstract

Correlation measurements imply that anisotropic flow in nuclear collisions includes a novel triangular component along with the more familiar elliptic-flow contribution. Triangular flow has been attributed to event-wise fluctuations in the initial shape of the collision volume. We ask two questions: 1) How do these shape fluctuations impact other event-by-event observables? 2) Can we disentangle fundamental information on the early time fluctuations from the complex flow that results? We study correlation and fluctuation observables in a framework in which flux tubes in an early Glasma stage later produce hydrodynamic flow. Calculated multiplicity and transverse momentum fluctuations are in excellent agreement with data from 62.4 GeV Au+Au up to 2.76 TeV Pb+Pb.