Higgs Decay Signal Strengths in an Extended 2HDM

Abstract

The combined CMS and ATLAS analysis of \(h \to Zγ\) reveals a \(2σ\) excess over the Standard Model (SM) prediction, hinting at potential new physics. In contrast, the observed agreement of \(μ_{γγ}\) with the SM imposes stringent constraints on such extension. In this context, we investigate a Two Higgs Doublet Model (2HDM) extended by a complex scalar singlet and a vector-like lepton (VLL). This framework successfully accommodates the Higgs decay signal strengths \(μ_{{}_{W \,W^\star}}\), \( μ_{Zγ}\,\), and \(\, μ_{γγ}\) while also satisfying precision electroweak constraints, the observed experimental value of muon \(g-2\), and bounds from LEP II data. We identify a viable region of parameter space that is consistent with all low energy data and current experimental limits on the Higgs decay signal strengths.

11 pages, 7 figures