Relative particle yield fluctuations in Pb-Pb collisions at ${\mathbf{\sqrt{s_{\rm NN}}=2.76}}$ TeV

TL;DR

This paper presents measurements of particle yield fluctuations in Pb-Pb collisions at 2.76 TeV using the ALICE detector, revealing centrality-dependent dynamical fluctuations and correlations among particle pairs.

Contribution

It introduces the novel Identity Method for measuring multiplicity moments with incomplete particle identification in heavy-ion collisions.

Findings

p/π fluctuations change sign from positive to negative in peripheral collisions

Results follow lower energy trends for central collisions

Significant correlations observed between particle pairs

Abstract

First results on K/$\pi$, p/$\pi$ and K/p fluctuations are obtained with the ALICE detector at the CERN LHC as a function of centrality in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. The observable $\nu_{\rm dyn}$, which is defined in terms of the moments of particle multiplicity distributions, is used to quantify the magnitude of dynamical fluctuations of relative particle yields and also provides insight into the correlation between particle pairs. This study is based on a novel experimental technique, called the Identity Method, which allows one to measure the moments of multiplicity distributions in case of incomplete particle identification. The results for p/$\pi$ show a change of sign in $\nu_{\rm dyn}$ from positive to negative towards more peripheral collisions. For central collisions, the results follow the smooth trend of the data at lower energies and $\nu_{\rm dyn}$ exhibits a change in sign for p/$\pi$ and K/p.