Electromagnetic and gravitational decay of the Higgs boson
  The decays of a scalar particle, of either parity, into two photons or into two gravitons are evaluated. The effective interactions are of the form $\phi FF, \phi F\tilde{F}$ or $\phi RR,\phi R\tilde{R}$; in particular, Higgs boson decay into gravitons cannot be adduced to an interaction $\phi R$, as has been recently claimed. 
R. Delbourgo and Dongsheng Liu