Explicit CP violation in the MSSM through Higgs →γγ

The MSSM with explicit CP violation is studied through the di-photon decay channel of the lightest neutral Higgs boson. Through the leading one-loop order H1→γγ is affected by a large number of Higgs-sparticle couplings, which could be complex. Our preliminary scan over the supersymmetric parameter space shows that more than 50% average deviations are possible, in either direction, in the corresponding branching ratio, with respect to the case of the CP-conserving MSSM. In particular, our analysis shows that in the presence of a light stop (with mass ∼200 GeV) a CP-violating phase ϕμ∼90° can render the H1→γγ branching ratio more than 10 times larger, for suitable combinations of the other MSSM parameters.