The Standard Model Higgs in $γγ$ Collisions

Abstract

For a Higgs boson below the $W^\pm$ threshold, the $γγ$ collider option of a future linear $e^+ e^-$ machine is compelling. In this case one can measure the ``gold-plated'' loop induced $Γ(H \longrightarrow γγ)$ partial width to high precision, testing various extensions of the Standard Model. With recent progress in the expected $γγ$ luminosity at TESLA, we find that for a Higgs of 115 GeV a statistical accuracy of the two photon partial width of 1.4 % is possible. The total width depends thus solely on the accuracy of $BR(H \longrightarrow γγ)$ and is of ${\cal O} (10 %)$.