Finite-size effects and the search for the critical endpoint of QCD

TL;DR

This paper investigates how finite system sizes in heavy ion collisions affect the QCD phase diagram and demonstrates finite-size scaling as a method to locate the critical endpoint using experimental data.

Contribution

It introduces finite-size scaling analysis to experimental heavy ion collision data to search for the QCD critical endpoint, considering realistic system sizes.

Findings

Finite-size effects significantly modify the chiral phase diagram.

RHIC data suggests the critical point is at     510 MeV or higher.

Predictions for fluctuation signals at lower energies are provided.

Abstract

Taking into account the finiteness of the system created in heavy ion collisions, we show sizable results for the modifications of the chiral phase diagram at volume scales typically encountered in current experiments and demonstrate the applicability of finite-size scaling as a tool in the experimental search for the critical endpoint. Using data from RHIC and SPS and assuming finite-size scaling, we find that RHIC data from 200 GeV down to 19.6 GeV is only consistent with a critical point at \mu \gtrsim 510 MeV. We also present predictions for the fluctuations at lower energies currently being investigated in the Beam Energy Scan program.