Energy spectra and energy correlations in the decayH→ZZ→μ⁺μ⁻μ⁺μ⁻

Abstract

It is shown that in the sequential decay$H \to ZZ \to (f_1 \bar f_1 ) + (f_2 \bar f_2 )$, the energy distribution of the final state particles provides a simple and powerful test of theHZZ vertex. For a standard Higgs boson, the energy spectrum of any final fermion, in the rest frame ofH, is predicted to be dΓ/dx∼1+β⁴−2(x−1)², with$\beta = \sqrt {1 - 4m_Z^2 /m_H^2 }$ and 1−β≤x=4E/m _H ≤1+β. By contrast, the spectrum for a pseudoscalar Higgs is dΓ/dx∼β²+(x−1)². There are characteristic energy correlations betweenf ₁ andf ₂ and betweenf ₁ andf ₂. These considerations are applied to the “gold-plated” reactionH→ZZ→μ⁺μ⁻μ⁺μ⁻, including possible effects ofCP-violation in theHZZ coupling. Our formalism also yields the energy spectra and correlations of leptons in the decay$H \to W^ + W^ - \to l^ + v_l l^ - \bar v_l$.