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

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 $n_0^{0}n$ 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.

2nd International Workshop on the physics of Ultra Peripheral Collisions (UPC 2025)