The thermal proton yield anomaly in Pb-Pb collisions at the LHC and its resolution

TL;DR

This paper resolves the proton yield discrepancy in Pb-Pb collisions at the LHC by incorporating pion-nucleon interactions and nonresonant correlations into the statistical hadronization model, aligning predictions with experimental data.

Contribution

It introduces a novel application of the S-matrix formulation to include interactions and correlations, improving the accuracy of proton yield predictions in heavy-ion collisions.

Findings

Proton yield predictions are reduced to match ALICE data.

Inclusion of pion-nucleon interactions and nonresonant correlations is crucial.

Lattice QCD results help estimate multi-pion-nucleon interactions.

Abstract

We propose a resolution of the discrepancy between the proton yield predicted by the statistical hadronization approach and data on hadron production in ultra-relativistic nuclear collisions at the LHC. Applying the S-matrix formulation of statistical mechanics to include pion-nucleon interactions, we reexamine their contribution to the proton yield, taking resonance widths and the presence of nonresonant correlations into account. The effect of multi-pion-nucleon interactions is estimated using lattice QCD results on the baryon-charge susceptibility. We show that a consistent implementation of these features in the statistical hadronization model, leads to a reduction of the predicted proton yield, which then quantitatively matches data of the ALICE collaboration for Pb-Pb collisions at the LHC.