The rare decay H → Zγ in perturbative QCD

The rare Higgs boson decay H → Zγ is forbidden at tree-level. In the Standard Model, it is loop-mediated through a W boson or a heavy quark. We analytically compute the QCD correction to the heavy quark loop, confirming earlier purely numerical results, that were obtained for on-shell renormalization. The small quark mass expansion of the decay matrix element contains only single-logarithmic contributions at each perturbative order, which is in contrast to the double logarithms observed in H → γγ. We investigate the numerical interplay of bottom and top quark contributions, and the dependence of the result on the renormalization scheme.