Non-Gaussian eccentricity fluctuations

Abstract

We study the fluctuations of the anisotropy of the energy density profile created in a high-energy collision at the LHC. We show that the anisotropy in harmonic $n$ has generic non-Gaussian fluctuations. We argue that these non-Gaussianities have a universal character for small systems such as p+Pb collisions, but not for large systems such as Pb+Pb collisions where they depend on the underlying non-Gaussian statistics of the initial density profile. We generalize expressions for the eccentricity cumulants $\varepsilon_2\{4\}$ and $\varepsilon_3\{4\}$ previously obtained within the independent-source model to a general fluctuating initial density profile.