Results on system size dependence of strangeness production in the CERN SPS energy range from NA61/SHINE

TL;DR

This paper presents measurements of charged kaon and pion production in various collision systems at CERN SPS energies, revealing a rapid change in hadron production properties with system size, especially from Be+Be to Ar+Sc.

Contribution

It provides new experimental data on system size dependence of strangeness production, highlighting the onset of significant kaon-to-pion ratio enhancement in Ar+Sc collisions.

Findings

Significant $K^+/\pi^+$ ratio enhancement in Ar+Sc compared to smaller systems.

Rapid change in hadron production properties from Be+Be to Ar+Sc.

Comparison of results with world data and theoretical models.

Abstract

NA61/SHINE is a multipurpose fixed-target facility at the CERN Super Proton Synchrotron. The main goals of the NA61/SHINE strong interactions program are to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. To reach these goals, hadron production measurements are performed in the form of a two-dimensional scan by varying collision energy and system size. The Collaboration has recently finished data acquisition for its original program on strong interactions, accumulating broad data samples on hadron production in various systems in the SPS energy range.\\ In this contribution, the NA61/SHINE results on identified charged kaon and pion production in p+p, Be+Be and Ar+Sc collisions at the SPS energy range ($\sqrt{s_{NN}}$=5.1--17.3 GeV) are presented. The NA61/SHINE measurements of small and intermediate-mass ion collisions establish an interesting system size dependence, showing a rapid change of hadron production properties that starts when moving from Be+Be to Ar+Sc system. In particular, Ar+Sc is the smallest system for which a significant enhancement of $K^+/\pi^+$ ratio with respect to $p$+$p$ collisions is observed. Obtained energy and system size dependence of the measured charged hadron multiplicities are compared with available world data and various theoretical models.