Enhancement of h --> gamma gamma in the Two Higgs Doublet Model Type I

Abstract

We show that in the Two Higgs Doublet Model (THDM) Type I the partial decay width of h --> gamma gamma can be considerably larger than in Type II, due to light charged scalars with a mass about 100 GeV, which are not yet excluded in Type I. A possible enhancement of the width compared to the SM is analyzed for different Higgs potentials, subject to constraints from tree-level unitarity, vacuum stability and electroweak precision tests.

Comments: 12 pages. v2: Sign error in eq. (19) corrected. Results and figures for the IDM changed accordingly. Other minor corrections. References and improved discussion of interference effects added