Two-photon decay width of the Higgs boson in left-right-symmetric theories

We calculate the $W_R$ contribution to the two-photon decay width of the light neutral Higgs boson $H_1^0$ in left-right-symmetric models. We find that this contribution is suppressed relative to the standard-model (SM) $W_L$ contribution by a factor ${\left(\frac{M_L}{M_R}\right)}^4$. This result arises because the $W_R$ coupling to $H_1^0$ is not proportional to its own mass $M_R$, as a SM-like coupling would suggest, but rather to the lighter mass $M_L$. As a consequence, $\Gamma (H_1^0\to \gamma \gamma )$ in left-right-symmetric theories has essentially the same value as in the standard model.