Detection of the heavy Higgs boson at $\gamma \gamma$ colliders

Abstract

We consider the possibility of detecting a heavy Higgs boson ($m_H>2m_Z$) in proposed $\gamma \gamma$ colliders through the semi-leptonic mode $\gamma \gamma \to H\to ZZ\to q\bar{q}{\ell }^{+}{\ell }^{-}$. We show that due to the non-monochromatic nature of the photon beams produced by the laser-backscattering method, the resultant cross section for Higgs production is much smaller than the on-resonance cross section and generally {\it decreases} with increasing collider energy. Although continuum $ZZ$ production is expected to be negligible, we demonstrate the presence of and calculate sizeable backgrounds from $\gamma \gamma \to {\ell }^{+}{\ell }^{-}Z,q\bar{q}Z$, with $Z\to q\bar{q},{\ell }^{+}{\ell }^{-}$, respectively, and $\gamma \gamma \to t\bar{t}\to b\bar{b}{\ell }^{+}{\ell }^{-}\nu \bar{\nu }$. This channel may be used to detect a Higgs of mass $m_H$ up to around 350~GeV at a 0.5~TeV $e^{+}{e}^{-}$ collider, assuming a nominal yearly luminosity of 10--20~fb${}^{-1}$.

Comments: 18 pages (in RevTeX) plus Postscript figures (available by email or FAX), NUHEP-TH-92-29 and DOE-309-CPP-47. (Revised version: NO CHANGES to the manuscript, simply removed corrupted figure files)