Charged particle pseudorapidity distributions measured with the STAR EPD

TL;DR

This paper reports on the measurement of charged particle pseudorapidity distributions using the upgraded STAR detector's Event Plane Detector, involving Monte Carlo simulations and unfolding techniques to correct for detector response.

Contribution

It introduces a method to measure charged particle pseudorapidity distributions with the STAR EPD, including detector response correction and systematic validation.

Findings

Charged particle distributions were successfully measured at 19.6 and 27.0 GeV.

The detector response matrix was accurately determined via Monte Carlo simulations.

Systematic checks confirmed the robustness of the unfolding method.

Abstract

In 2018, in preparation for the Beam Energy Scan II, the STAR detector was upgraded with the Event Plane Detector (EPD). The instrument enhanced STAR's capabilities in centrality determination for fluctuation measurements, event plane resolution for flow measurements and in triggering overall. Due to its fine radial granularity, it can also be utilized to measure pseudorapidity distributions of the produced charged primary particles, in EPD's pseudorapidity coverage of $2.15<|\eta|<5.09$. As such a measurement cannot be done directly, the response of the detector to the primary particles has to be understood well. The detector response matrix was determined via Monte Carlo simulations and corrected charged particle pseudorapidity distributions were obtained in Au+Au collisions at center of mass collision energies $\sqrt{s_{_{NN}}}$ = 19.6 and 27.0 GeV using an iterative unfolding procedure. Several systematic checks of the method were also done.