Branching Ratios of $H_{1,2,3} \rightarrow μ^{+}μ^{-}$ in the Broken-Phase N2HDM
T. V. Obikhod, Ie. O. Petrenko
TL;DR
The paper addresses how the Higgs coupling to second-generation fermions can reveal new physics in extended Higgs sectors. It computes the branching ratios $BR(H_i \to μ^+ μ^-)$ for all CP-even states in the broken-phase N2HDM, including leading one-loop radiative corrections, and benchmarks against the ATLAS measurement $μ=1.4 \pm 0.4$ to constrain the parameter space defined by $\tan\beta$, the singlet VEV $v_S$, and scalar masses. The results show $H_1 \to μ^+ μ^-$ remains SM-like across all Yukawa types, while $H_2$ and $H_3$ exhibit type-dependent enhancements or suppressions spanning several orders of magnitude, with Type II and Type X offering the strongest discovery potential in current data. The study demonstrates that precise dimuon measurements provide a sensitive probe of extended Higgs sectors and can guide searches at the LHC and future colliders.
Abstract
Recent evidence from the ATLAS Collaboration for the rare decay $H \rightarrow μ^{+}μ^{-}$ provides a unique window into the Higgs boson's coupling to second-generation fermions. In this work, we investigate how this signal can probe physics beyond the Standard Model by computing the branching ratios $B(H_{i} \rightarrow μ^{+}μ^{-})$ for the three CP-even Higgs bosons $H_{1,2,3}$ in the broken-phase Next-to-Two-Higgs-Doublet Model (N2HDM). We incorporate one-loop radiative corrections and analyze deviations from the Standard Model prediction due to modified Yukawa couplings, scalar mixing, and singlet--doublet interactions. By confronting our results with the ATLAS signal strength $μ= 1.4 \pm 0.4$, we identify viable regions of the N2HDM parameter space, characterized by tan$β$, the singlet vacuum expectation value, and scalar masses, and assess the model's capacity to explain potential enhancements in the dimuon channel. Our study demonstrates that precision measurements of $H \rightarrow μ^{+}μ^{-}$ serve as a powerful tool to test extended Higgs sectors and uncover new physics at current and future colliders.