Z-boson pair production via vector boson scattering and the search for the Higgs boson at hadron supercolliders

Abstract

We present the results of a complete perturbative calculation of Z-boson pair production via the O( α W 4) electroweak process qq → qqZZ, and the O( α s 2 α W 2) mixed QCD-electroweak processes, gg → q q ZZ , qg → qgZZ, q q → ggZZ and qq → qqZZ at supercollider energies. Compact analytic expressions for the helicity amplitudes for all contributing diagrams, including the subsequent decay of the Z boson into massless fermions and all interference effects, are given. Detailed results for the event characteristics and the jet activity in electroweak qq → qqZZ events are presented for the full range of invariant masses of the Z pair, m ZZ, as well as in the Higgs boson resonance region, m ZZ = m H ± Γ H, where we compare the results of the exact calculation with the effective W approximation, and the approximation where only s-channel Higgs resonance diagrams are taken into account. We also compute the background resulting from the mixed QCD-electroweak ZZ + 2 jet processes at large jet transverse momenta in the resonance region and suggest techniques to suppress this background. Cross sections for Higgs boson production in the ZZ channel and the continuum ZZ background, in association with up to 2 jets, are given. We find that jet identification in the forward rapidity region,  η j  > 2.5 may considerably facilitate the detection of a heavy Higgs boson with m H ∼ O(1 TeV) at the LHC and SSC.