Neutral Pion-like Resonances at Photon Colliders

Abstract

Two photons can annihilate into a neutral pion-like resonance via the anomaly coupling, just like ${\pi }^0\gamma \gamma$ in QCD. In some strongly interacting electroweak symmetry breaking models, e.g., technicolor type models, there often exist neutral pion-like resonances. TeV photon colliders have a strong capability to discover such particles, because the standard model background in photon scattering goes through box diagrams and is therefore highly suppressed. In this study, we perform a signal-background comparison. We show that $e^{+}{e}^{-}$ linear colliders running in $\gamma \gamma$ mode can discover such neutral-pion-like resonances with a decent sensitivity.

Comments: 10 pages, better figures, added discussion and references