The SM expected branching ratio for h → γ γ and an excess for h → Z γ

Combination of recent measurements for h → Z γ from ALTLAS and CMS shows an excess that the ratio of the observed and standard model (SM) predicted branching ratios μ = (σ· B)obs/(σ· B)SM is 2.2± 0.7. If confirmed, it is a signal of new physics (NP) beyond SM. We study NP explanation for this excess. In general, for a given model it also affects the process h → γ γ. Since measured branching ratio for this process agrees with SM prediction well, the model is constrained severely. We find that a minimally fermion singlets and doublet extended NP model can explain simultaneously the current data for h → Z γ and h→ γγ. There are two solutions. One is the SM amplitude cZSM is enhanced by δ cZ for h → Z γ to the observed value, but the h → γ γ amplitude c_γSM +δ c_γ is decreased to -c_γSM to give the observed branching ratio. This seems to be a contrived solution that although cannot be ruled out simply using branching ratio measurements. We, however, find another solution which naturally enhances the h → Z γ to the measured value, but keeps the h → γγ close to its SM prediction. We also comment on some phenomenology of these new fermions.