# Primordial non-Gaussianity in heavy-ion collisions

## TL;DR

This paper demonstrates that cumulants of anisotropic flow in heavy-ion collisions reveal the non-Gaussian nature of the initial energy density fluctuations, with experimental data indicating a positively skewed distribution.

## Contribution

It introduces a perturbative approach to connect flow cumulants with initial density fluctuations, highlighting the non-Gaussian features of the early-stage energy distribution.

## Key findings

- Flow cumulants probe non-Gaussian initial conditions.
- Negative $sc(3,2)$ indicates positive skewness in energy distribution.
- Perturbative expansion links flow correlations to density fluctuations.

## Abstract

We show that experimental data on cumulants of anisotropic flow in heavy-ion collisions probe the non-Gaussian statistics of the energy density field created right after the collision. We carry out a perturbative expansion of the initial anisotropies of the system in terms of its density fluctuations. We argue that the correlation between the magnitudes of elliptic flow and triangular flow, dubbed $sc(3,2)$, is generically of the same sign and order of magnitude as the kurtosis of triangular flow in a hydrodynamic picture. The experimental observation that these quantities are negative implies that the distribution of energy around a given point has positive skew.