Theoretical basis of Higgs-spin analysis in H→γγ and Zγ decays

We chart the theoretical basis of radiative decays of the Higgs boson, H→γγ and Zγ, for measuring the spin of the Higgs particle. These decay channels are complementary to other rare modes such as real/virtual Z-boson pair decays. In systematic helicity analyses the angular distribution for zero-spin is confronted with hypothetical spin-2± and higher assignments to quantify the sensitivity.