Probing the structure of the initial state of heavy-ion collisions with $p_T$-dependent flow fluctuations

TL;DR

This paper extends the understanding of initial-state geometry in heavy-ion collisions by linking $p_T$-differential flow fluctuations to small-scale initial structures, revealing new details of the hydrodynamic response.

Contribution

It introduces a method to connect $p_T$-dependent flow fluctuations with initial-state structures, enhancing the analysis of heavy-ion collision dynamics.

Findings

Subleading flow components reveal small-scale initial structures.

Extended mapping includes $p_T$-differential flow.

Provides new insights into hydrodynamic response mechanisms.

Abstract

The connection between initial-state geometry and anisotropic flow can be quantified through a well-established mapping between $p_T$-integrated flow harmonics and cumulants of the initial transverse energy distribution. In this paper we successfully extend this mapping to also include $p_T$-differential flow. In doing so, we find that subleading principal components of anisotropic flow can reveal previously unobserved details of the hydrodynamic response, in both the linear and the nonlinear regimes. Most importantly, we show that they provide novel information on the small-scale structures present in the initial stage of relativistic heavy-ion collisions.