Bayesian approach to long-range correlations and multiplicity fluctuations in nucleus-nucleus collisions

Abstract

The number of particles detected in a nucleus-nucleus collision strongly depends on the impact parameter of the collision. Therefore, multiplicity fluctuations, as well as rapidity correlations of multiplicities, are dominated by impact parameter fluctuations. We present a method based on Bayesian inference which allows for a robust reconstruction of fluctuations and correlations at fixed impact parameter. We apply the method to ATLAS data on the distribution of charged multiplicity and transverse energy. We argue that multiplicity fluctuations are smaller at large rapidity than around central rapidity. We suggest simple, new analyses, in order to confirm this effect.

Comments: 13 pages, 11 figures; v2: published version with some added explanations and rephrasing of our presentation, especially in Part II. Code for 2D Bayesian reconstruction of ATLAS data is included as ancillary file