HadroTOPS: A Monte Carlo Event Generator For Hadron Production In Two-Photon Scattering In Electron Positron Collisions

We present a Monte Carlo event generator specifically developed for the study of hadronic two-photon fusion events in two-photon scattering at electron-positron colliders. The code enables the generation of events with exact leading-order QED coupling and a flat phase space decay of the hadronic state into an arbitrary number of final state particles as selected by the user. Thus, this generator is well-suited for the use of partial wave analyses tools to study the two-photon production of higher-multiplicity final states across a wide range of energies and photon virtualities. Furthermore, the code integrates both experimental and theoretical inputs on the two-photon couplings of hadrons to simulate two-photon production processes. Motivated by the investigations of the BESIII collaboration, the final states $\pi^+\pi^-$, $\pi^0\pi^0$, $\pi^0\eta$, $K^+K^-$, $K^0_SK^0_S$, $\eta\eta$, and $f_1(1285)\to \eta\pi^+\pi^-$ via $a_0^\pm(980)\pi^\mp$ and $f_0(500)\eta$ are currently included. The code is sufficiently flexible to easily add additional final states as well as quickly change the already included channels.