Diphoton elastic scattering in UPC at smaller $W_{\gamma\gamma}$

TL;DR

This paper investigates photon-photon scattering at low energies below 5 GeV, including contributions from mesonic resonances and background processes, with implications for experiments at ALICE and LHCb.

Contribution

It extends previous high-energy calculations to the low mass range, analyzing mesonic resonance contributions and background reduction strategies in photon-photon scattering.

Findings

Resonance contributions from $ ext{η}$ and $ ext{η'}$ mesons are significant below 5 GeV.

Background from $ ext{π}^0 ext{π}^0$ decays can be mitigated with kinematic cuts.

Results are tailored for ALICE and LHCb experimental conditions.

Abstract

We present a study of photon-photon scattering for $W_{\gamma\gamma} < 5$ GeV. We extend earlier calculations of this cross section for $W_{\gamma\gamma}>$ 5 GeV into the low mass range where photoproduction of the pseudoscalar mesons $\eta$(548), $\eta^{'}(958)$ and other mesonic resonances contribute to the two-photon final states. We consider the dominant background of the two photon final state which arises from $\gamma \gamma$ decays of photoproduced $\pi^{0} \pi^0$-pairs. We discuss how to reduce the background by imposing cuts on different kinematical variables. We present results for ALICE and LHCb kinematics.