A Golden-Channel Higgs Decay

Abstract

With a Higgs mass greater than 190 GeV and lower than 300 GeV, the decay channel H --> ZZ --> 4l becomes what is referred to as the golden channel for Higgs decay (clean signal). Suppose a pair of on shell Zs with an invariant mass of 200 GeV are seen, but the event rate exceeds the theoretically expected value for the SM Higgs. What mechanisms beyond the Standard Model could provide such enhancements? Such ZZ states could come from a decaying particle of spin 0,1 or 2. In addition the ZZ state exhibits a high degree of symmetry that limit the possible couplings. Theories considered include mainly Z' and 2HDM. Technicolor and extra-dimensional theories like LED and RS scenarios are also discussed.