$K^-$ and $\bar p$ Spectra for Au+Au Collisions at $\sqrt{s}$ = 200 GeV from STAR, PHENIX and BRAHMS in Comparison to Core-Corona Model Predictions

TL;DR

This paper extends the core-corona model to analyze the centrality dependence of $K^-$ and $ar{p}$ spectra in Au+Au collisions at 200 GeV, highlighting data discrepancies among experiments and questioning collective expansion interpretations.

Contribution

It applies the core-corona model to new particle spectra and discusses the impact of experimental differences on model parameters and interpretations.

Findings

Model describes centrality dependence of spectra well for some particles.

Data discrepancies affect model parameter extraction.

Centrality dependence of average momentum varies with particle species.

Abstract

Based on results obtained with event generators we have launched the core-corona model. It describes in a simplified way but quite successfully the centrality dependence of multiplicity and $<p_t>$ of identified particles observed in heavy-ion reaction at beam energies between $\sqrt{s}$ = 17 GeV and 200 GeV. Also the centrality dependence of the elliptic flow, $v_2$, for all charged and identified particles could be explained in this model. Here we extend this analysis and study the centrality dependence of single particle spectra of $K^-$ and ${\bar p}$ measured by the PHENIX, STAR and BRAHMS collaborations. We find that also for these particles the analysis of the spectra in the core-corona model suffers from differences in the data published by the different experimental groups, notably for the pp collisions. As for protons and $K^+$ for each experience the data agree well with the prediction of the core-corona model but the value of the two necessary parameters depends on the experiments. We show as well that the average momentum as a function of the centrality depends in a very sensitive way on the particle species and may be quite different for particles which have about the same mass. Therefore the idea to interpret this centrality dependence as a consequence of a collective expansion of the system, as done in blast way fits may be premature.