# Event activity measurements and mid-rapidity correlations in 200 GeV p+Au collisions at STAR

## TL;DR

This paper presents preliminary measurements of correlations in 200 GeV p+Au collisions at STAR, providing insights into the use of the Glauber model and centrality binning in small systems, with implications for nuclear modification studies.

## Contribution

It offers new experimental data on event activity correlations in p+Au collisions, highlighting issues with current centrality determination methods in small systems.

## Key findings

- Correlations support concerns about centrality binning in p+Au.
- Results suggest using semi-inclusive jet spectra for better nuclear modification analysis.
- Findings inform the debate on Glauber model applicability in small collision systems.

## Abstract

These proceedings report preliminary measurements of correlations between mid-rapidity charged tracks and high-rapidity event activity (EA) at STAR for $\sqrt{s_\mathrm{NN}}= 200\, \mathrm{GeV}$ p+Au collisions taken in 2015. These correlations are intriguing because they inform the current debate over use of the Glauber model in `small' systems (here meaning p+A or d+A and denoted as `s+A') and have implications for calculating nuclear modification and quenching observables in these systems. The results support concerns about centrality binning in p+Au collisions, and as such motivate using ratios of semi-inclusive, as opposed to fully inclusive, jet spectra to look for jet enhancement or suppression.