Investigating the onset of deconfinement with NA61/SHINE

TL;DR

NA61/SHINE investigates the onset of deconfinement in strongly interacting matter through a comprehensive energy and system size scan, analyzing hadron production and baryon transport in nucleus-nucleus collisions at CERN SPS.

Contribution

This study provides new experimental data on hadron spectra and baryon transport, enhancing understanding of deconfinement phenomena at SPS energies.

Findings

The $K^+/\pi^+$ ratio shows features indicative of the onset of deconfinement.

Comparison of proton rapidity spectra reveals energy and system-size dependence of baryon transport.

Results extend previous NA49 findings and include new data from Xe+La and Ar+Sc collisions.

Abstract

NA61/SHINE is a multipurpose fixed-target experiment located at the CERN SPS. One of its main goals is to study the onset of deconfinement and the properties of strongly interacting matter. For this purpose, a unique two-dimensional scan in collision energy ($\sqrt{s_\mathrm{NN}} = 5.12 - 16.8/17.3$~GeV) and system size (from $p$+$p$ to Pb+Pb) was performed. Results on hadron spectra produced in nucleus-nucleus collisions, including the recent data on charged hadrons produced in central Xe+La collisions and baryons in central Ar+Sc collisions, are presented. The kinematic distributions and the measured multiplicities of identified hadrons are compared with NA49 Pb+Pb results and with available world data. The obtained results, particularly the $K^+/\pi^+$ ratio, are crucial for understanding the phenomena of the onset of deconfinement, which is one of the main aims of the strong interaction program of the NA61/SHINE Collaboration. Additionally, a comparison of proton rapidity spectra in nucleus-nucleus collisions from NA61/SHINE and NA49 is presented, providing a complete picture of the energy and system-size dependence of the mechanism of transport of baryon number at SPS energies.