Low-mass Higgs decays to four leptons at one loop and beyond

Abstract

The ongoing searches for Higgs-boson signals in data taken at the CERN LHC and the Fermilab Tevatron crucially rely on the decay channels $H\ensuremath{\rightarrow}Z\ensuremath{\ell}\ensuremath{\ell}$ and $H\ensuremath{\rightarrow}W\ensuremath{\ell}{\ensuremath{\nu}}_{l}$. We present a precision study of the partial widths of these decay channels including the full one-loop electroweak corrections and the dominant contributions at two and three loops, of $\mathcal{O}({G}_{F}^{2}{m}_{t}^{4})$, $\mathcal{O}({G}_{F}{m}_{t}^{2}{\ensuremath{\alpha}}_{s})$, and $\mathcal{O}({G}_{F}{m}_{t}^{2}{\ensuremath{\alpha}}_{s}^{2})$. Since the invariant mass of the off-shell intermediate boson is relatively low in the mass window $115\text{ }\text{ }\mathrm{GeV}<{m}_{H}<129\text{ }\text{ }\mathrm{GeV}$ of current interest, lepton mass effects are relevant, especially for the $\ensuremath{\tau}$ lepton.