Measurements of $\pi^\pm$, $K^\pm$, $p$ and $\bar{p}$ spectra in $^{40}$Ar+$^{45}$Sc collisions at 13$A$ to 150$A$ GeV/$c$

TL;DR

This study measures the spectra of various hadrons produced in argon-scandium collisions at different energies to explore how system size affects particle production, revealing trends that challenge existing models.

Contribution

It provides new experimental data on hadron spectra in Ar+Sc collisions across multiple energies, highlighting system-size effects not explained by current models.

Findings

Energy dependence of $K^ extpm$/$\pi^ extpm$ ratios is intermediate between p+p and Pb+Pb collisions.

Inverse slope parameters of $K^ extpm$ transverse mass distributions show similar intermediate behavior.

Results indicate a system-size dependence of hadron production properties that current models cannot explain.

Abstract

The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in collisions of nuclei of varied sizes. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of $\pi^\pm$, $K^\pm$, $p$ and $\bar{p}$ produced in $^{40}$Ar+$^{45}$Sc collisions at beam momenta of 13$A$, 19$A$, 30$A$, 40$A$, 75$A$ and 150$A$~\GeVc. The analysis uses the 10\% most central collisions, where the observed forward energy defines centrality. The energy dependence of the $K^\pm$/$\pi^\pm$ ratios as well as of inverse slope parameters of the $K^\pm$ transverse mass distributions are placed in between those found in inelastic $p$+$p$ and central Pb+Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.