Scaling properties in bulk and p$_{\rm T}$-dependent particle production near midrapidity in relativistic heavy ion collisions

TL;DR

This study analyzes how particle production scales with collision centrality and energy in heavy ion collisions at RHIC, revealing similar behaviors in different systems and minimal impact of multiple nucleon collisions on bulk and intermediate pT particle yields.

Contribution

It demonstrates that particle production scaling properties are consistent across different collision systems and energies, with factorization and minimal multiple collision effects.

Findings

Similar multiplicity densities in Au+Au and Cu+Cu for same N_part

Yield ratios are constant across energies and centralities

Multiple nucleon collisions have minor influence on particle yields

Abstract

The centrality dependence of the midrapidity charged-particle multiplicity density ($|\eta|$$<$1) is presented for Au+Au and Cu+Cu collisions at RHIC over a broad range of collision energies. The multiplicity measured in the Cu+Cu system is found to be similar to that measured in the Au+Au system, for an equivalent N$_{\rm part}$, with the observed factorization in energy and centrality still persistent in the smaller Cu+Cu system. The extent of the similarities observed for bulk particle production is tested by a comparative analysis of the inclusive transverse momentum distributions for Au+Au and Cu+Cu collisions near midrapidity. It is found that, within the uncertainties of the data, the ratio of yields between the various energies for both Au+Au and Cu+Cu systems are similar and constant with centrality, both in the bulk yields as well as a function of p$_{\rm T}$, up to at least 4 GeV/$c$. The effects of multiple nucleon collisions that strongly increase with centrality and energy appear to only play a minor role in bulk and intermediate transverse momentum particle production.