Strange Particle Production at RHIC

TL;DR

This paper presents measurements of strange particle yields in Cu+Cu and Au+Au collisions at 200 GeV, revealing higher strangeness production in Cu+Cu at fixed participant number, challenging existing models.

Contribution

It provides new experimental data on strange particle production and compares these results with theoretical models, highlighting discrepancies with canonical predictions.

Findings

Strangeness production is higher in Cu+Cu than in Au+Au at the same participant number.

AMPT and EPOS models qualitatively reproduce the data.

Strangeness scales better with the number of participants undergoing multiple collisions.

Abstract

We report STAR measurements of mid-rapidity yields for the $\Lambda$, $\bar{\Lambda}$, $K^{0}_{S}$, $\Xi^{-}$, $\bar{\Xi}^{+}$, $\Omega^{-}$, and $\bar{\Omega}^{+}$ particles in Cu+Cu and Au+Au $\sqrt{s_{NN}} = 200$ GeV collisions. We show that at a given number of participating nucleons, bulk strangeness production is higher in Cu+Cu collisions compared to Au+Au collisions at the same center of mass energy, counter to predictions from the Canonical formalism. We compare both the Cu+Cu and Au+Au yields to AMPT and EPOS predictions, and find they reproduce key qualitative aspects of the data. Finally, we investigate other scaling parameters and find bulk strangeness production for both the measured data and theoretical predictions, scales better with the number participants that undergo more than one collision.