STARlight: A C++ Object-Oriented Monte Carlo Event Generator for Ultra-Peripheral Collisions

Abstract

Ultra-peripheral collisions occur when nuclei pass one another without overlapping. The intense electric fields present can be treated as a flux of virtual photons; these photons can interact with the other nucleus or each other, producing a range of particles, including vector mesons and lepton pairs. In order to effectively study ultraperipheral collisions, a Monte Carlo event generator was created to simulate ultrarelativistic Au-Au interactions. This was initially written in FORTRAN in 1995, and used by the STAR Collaboration to optimize particle selection criteria and to assess whether rarer physics processes were possible to study at RHIC. Since then, changes have been made to the program to fit the needs of newer experiments and as a result, different versions have been created. I will present the physics modeled by the program, upgrades made to the Monte Carlo since 1995, and comparisons to data. My work has been to consolidate the various existing versions into one C++ application and to extend it to include additional final states, asymmetric collisions of d-Au, improved expandability, and the ability to generate 100,000 events in 13 minutes on a personal computer.