Net-proton probability distribution in heavy ion collisions

TL;DR

This paper analyzes net-proton probability distributions in heavy ion collisions using the hadron resonance gas model, comparing predictions with STAR data and exploring deviations in central collisions.

Contribution

It provides the first detailed comparison of net-proton distributions in heavy ion collisions with the hadron resonance gas model, highlighting deviations in central collisions.

Findings

Peripheral collision data agree with the model.

Central collision data show significant deviations.

Deviations are not due to model parameter uncertainties.

Abstract

We compute net-proton probability distributions in heavy ion collisions within the hadron resonance gas model. The model results are compared with data taken by the STAR Collaboration in Au-Au collisions at sqrt(s_{NN})= 200 GeV for different centralities. We show that in peripheral Au-Au collisions the measured distributions, and the resulting first four moments of net-proton fluctuations, are consistent with results obtained from the hadron resonance gas model. However, data taken in central Au-Au collisions differ from the predictions of the model. The observed deviations can not be attributed to uncertainties in model parameters. We discuss possible interpretations of the observed deviations.