Speaker
Description
Ultra-peripheral collisions of heavy ions (UPCs) serve as a valuable source of experimental data for studies of photon-photon interactions. One of the latest examples is the evidence of light-by-light scattering process (LbyL) first established by the CMS and ATLAS collablorations at the LHC. UPCs were also proposed as a tool for searches of effects of physics beyond the Standard Model (BSM), such as production of axion-like particles, $\gamma\gamma \rightarrow a \rightarrow \gamma\gamma$, and possible deviations of the anomalous magnetic moment of tau lepton $a_{\tau}$ from the Standard Model value. In addition to growing interest in BSM studies, dilepton production measurements also attract attention. Precise measurements of muon pair production in UPCs were recently obtained by the ATLAS collaboration, and considerable deviations of measured cross sections from available theoretical predictions were observed.
To address these physics topics, we developed a Monte Carlo event generator of photon-photon interactions in UPCs, Upcgen. The generator is based on the equivalent photon approximation with a refined treatment of the photon flux. The program includes production of lepton pairs with a possibility to set an arbitrary value of the lepton anomalous magnetic moment and account for photon polarization effects. Upcgen also supports LbyL process as well as neutral pion pair production which is considered to be one of the main sources of background photons in LbyL measurements at low diphoton masses $m_{\gamma\gamma} < 5$ GeV/$c^2$. In the simulation process, a significant performance increase can be achieved by using parallel computation to generate an amount of statistics sufficient for reasonable estimates in a short period of time.
In this presentation, a detailed review of the theoretical framework of the program will be given, as well as a description of the key parts of the implementation.
| Submitted on behalf of a Collaboration? | No |
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