Looking for the phase transition - recent NA61/SHINE results

TL;DR

The NA61/SHINE experiment investigates the phase diagram of strongly interacting matter by measuring particle spectra and fluctuations across different collision systems and energies, aiming to identify the critical point and deconfinement onset.

Contribution

This paper presents new results on fluctuations in Ar+Sc collisions and reports preliminary signs of size-dependent effects related to the phase transition region.

Findings

Observation of transverse momentum and multiplicity fluctuations in Ar+Sc collisions.

Identification of rapid changes in system size dependence, indicating a possible percolation threshold.

Evidence suggesting proximity to the hadronic phase transition region.

Abstract

The fixed-target NA61/SHINE experiment (SPS CERN) looks for the critical point of strongly interacting matter and the properties of the onset of deconfinement. It is a two dimensional scan of measurements of particle spectra and fluctuations in proton-proton, proton-nucleus and nucleus-nucleus interactions as a function of collision energy and system size, corresponding to a two dimensional phase diagram (temperature T - baryonic chemical potential $\mu_B$). New NA61/SHINE results are presented here, such as transverse momentum and multiplicity fluctuations in Ar+Sc collisions compared to NA61/SHINE p+p and Be+Be data, as well as to earlier NA49 A+A results. Recently, a preliminary signature for the new size dependent effect - rapid changes in system size dependence was observed in NA61-SHINE data, labeled as percolation threshold or onset of fireball. This would be closely related to the vicinity of the hadronic phase transition region.