Anomalous Couplings in Single Higgs Production through $γγ$ Collisions

Abstract

We show that single Higgs production in $γγ$ collisions through laser backscattering provides the best way to look for New Physics (NP) effects inducing anomalous Higgs couplings. Our analysis is based on the four $dim=6$ operators $Ø_{UB}$, $Ø_{UW}$, $\olØ_{UB}$ and $\olØ_{UW}$ which describe New Physics effects in this sector. Using the Higgs production rate we establish observability limits for the couplings of the aforementioned operators at a level of $10^{-3}$, which means establishing lower bounds on the scale of NP of the order 30 to 200 TeV. Higgs branching ratios, especially the ratio $Γ(H\toγγ)/Γ(H\toγZ)$, are shown to provide powerful ways to disentangle the effects of the various operators.