OBSERVABILITY OF A HEAVY HIGGS BOSON AT HADRON SUPERCOLLIDERS

We present a coherent analysis of Higgs-boson production in the channels pp --> ZZX --> l+l-l'+l'-X (l,l' = e, mu) and pp --> ZZX --> l+l-nu-nu-XBAR (nu = nu-e, nu-mu, nu-tau) for m(H) greater-than-or-equal-to 600 GeV at hadron supercolliders, using the exact matrix elements for gg --> ZZ and qq --> qqZZ. The importance of a complete understanding of the shape of the perturbative pp --> ZZX background from nonresonant diagrams is emphasized. We find that for the CERN Large Hadron Collider (LHC) to have a Higgs-boson discovery potential comparable to that of the Superconducting Super Collider (SSC) requires at least a factor of 10 times more integrated luminosity. In particular, assuming an integrated luminosity of 10(4) pb-1 and perfect lepton identification efficiency, the LHC (SSC) can identify Higgs bosons as resonances with mass up to 600 (800) GeV in pp --> ZZX --> l+l-l'+l'-X. To extend the discovery range of the LHC to m(H) = 800 GeV in this channel requires an integrated luminosity of at least 10(5) pb-1. For m(H) > 800 GeV, a clear resonance structure is missing; however, one can still discriminate between a heavy Higgs boson with m(H) approximately 1 TeV and a light Higgs boson (m(H) less-than-or-similar-to 2M(z)) at the SSC.