Ratio of baryon and electric-charge cumulants at second order with acceptance corrections

TL;DR

This paper analyzes the ratio of baryon and electric-charge cumulants at second order from experimental data, applying acceptance corrections, and compares the results with theoretical models to infer properties of the thermal medium.

Contribution

It introduces a method to correct for acceptance effects in cumulant ratios and compares experimental results with theoretical models to extract medium properties.

Findings

The cumulant ratio depends on the rapidity window.

The medium's temperature is inferred to be lower than the chemical freezeout temperature.

Acceptance corrections significantly impact the cumulant ratio analysis.

Abstract

We evaluate the ratio of baryon and electric-charge cumulants at second order from the recent experimental results at $\sqrt{s_{_{NN}}}=200$ GeV by the STAR Collaboration. The baryon number cumulant is reconstructed from the proton number distribution, and effects of the finite acceptance on the transverse momentum are corrected assuming the independent particle emission. We show that the obtained ratio has a dependence on the rapidity window. Comparison of the result with the hadron resonance gas model and lattice QCD numerical simulations suggests that if the fluctuations are generated from a thermal medium its temperature is significantly lower than the chemical freezeout temperature.