Photon-Photon Scattering at the Photon Linear Collider
G. Jikia, A. Tkabladze
TL;DR
The paper addresses the observability of photon-photon scattering, a fundamental one-loop SM process, at a Photon Linear Collider (PLC) realized through Compton backscattering of laser photons. It derives explicit analytic expressions for the $W$-boson loop contributions to the $\gamma\gamma \to \gamma\gamma$ helicity amplitudes in terms of scalar integrals and analyzes their low- and high-energy behavior, showing that $W$-loop amplitudes can dominate at high energies. Cross sections are computed for both monochromatic and spectrum-averaged photon collisions, including polarization and experimental cuts; the results indicate that above $200$--$250$ GeV in $\gamma\gamma$ collisions, the $W$-loop dominates, and at $\sqrt{s_{e^+e^-}} = 500$ GeV with $M_{\gamma\gamma}>250$ GeV one expects about 50 signal events in 10 fb$^{-1}$, with backgrounds suppressed by kinematic cuts and polarization. This work provides a clean SM test of one-loop non-Abelian gauge structure and offers a route to probe anomalous $W$-boson vertices through a purely loop-induced process.
Abstract
Photon-photon scattering at the Photon Linear Collider is considered. Explicit formulas for helicity amplitudes due to $W$ boson loops are presented. It is shown that photon-photon scattering should be easily observable at PLC and separation of the $W$ loop contribution (which dominates at high energies) will be possible at $e^+e^-$ c.m. energy of 500~GeV or higher.