Initial fluctuations and power spectrum of flow anisotropies in relativistic heavy-ion collisions

TL;DR

This paper reviews how flow anisotropies and their power spectrum in relativistic heavy-ion collisions reveal initial state fluctuations, drawing parallels with cosmic microwave background studies, and discusses recent measurement techniques and magnetic field effects.

Contribution

It provides a concise review of recent developments in measuring flow coefficients, the impact of initial magnetic fields, and the connection to initial parton distributions relevant for upcoming electron-ion collider experiments.

Findings

Flow coefficients encode initial state fluctuations.

Magnetic fields influence flow anisotropies.

Techniques for measuring higher flow coefficients have advanced.

Abstract

Flow has emerged as a crucial probe for the properties of the thermalized medium produced in relativistic heavy-ion collisions. The evolution of initial state fluctuations leaves imprints on the power spectrum of flow coefficients. Therefore flow coefficients are a crucial probe of initial state fluctuations arising from the parton distributions of the colliding nuclei. This has a very strong correspondence with the physics of power spectrum of cosmic microwave background radiation (CMBR) anisotropies which directly probes initial inflationary fluctuations. Much work has been done to probe these interesting interconnections, in particular, in developing techniques for the measurements of higher flow coefficients. We present a short review of these developments. The effect of initial magnetic field on these features will also be reviewed. All this acquires special importance in view of upcoming electron-ion collider which will directly probe initial parton distribution of the colliding nucleus.