Describing UPC Data with the Sar$t$re Event Generator

TL;DR

This paper discusses enhancements to the Sar$t$re Monte Carlo generator, improving its ability to simulate ultra-peripheral heavy-ion collisions and match experimental data by incorporating detailed photon flux and neutron tagging features.

Contribution

The paper introduces new features in Sar$t$re, including full photon flux modeling, interference effects, photon $k_T$, and neutron tagging, advancing the simulation accuracy for UPC data.

Findings

Improved agreement with STAR and LHCb data at small $p_T^2$

Enhanced neutron-tagged event classification

Better reproduction of experimental UPC distributions

Abstract

Ultra-peripheral heavy-ion collisions (UPCs) provide a distinct environment for high-energy QCD research, focusing on the production of vector mesons. This proceeding details recent advancements in the Sar$t$re Monte Carlo event generator, a dipole model-based tool, to better describe UPC data. We present the incorporation of the full photon flux, accounting for interference effects and photon transverse momentum ($k_T$), and the integration of an $n_0^0n$ afterburner for neutron-tagged event classification. These extensions significantly improve Sar$t$re's ability to reproduce experimental data from STAR and LHCb, particularly at small $p_T^2$ and for various neutron event classes.