Decays of the neutral Higgs bosons into SM fermions and gauge bosons in the $\mathcal{CP}$-violating NMSSM

TL;DR

This paper performs detailed one-loop calculations of neutral Higgs boson decays into SM particles within the CP-violating NMSSM, revealing significant radiative corrections and exploring phenomenological implications of light singlet-like states.

Contribution

It provides the first comprehensive one-loop decay width calculations for NMSSM Higgs bosons, including higher-order QCD corrections, and analyzes their phenomenological impact.

Findings

Decay widths of heavy Higgs bosons are dominated by radiative corrections.

Tree-level approximations often fail for electroweak gauge boson decays.

A light singlet-like Higgs could explain LEP and CMS excesses around 98 GeV.

Abstract

The Next-to-Minimal Supersymmetric Standard Model (NMSSM) offers a rich framework embedding physics beyond the Standard Model as well as consistent interpretations of the results about the Higgs signal detected at the LHC. We investigate the decays of neutral Higgs states into Standard Model (SM) fermions and gauge bosons. We perform full one-loop calculations of the decay widths and include leading higher-order QCD corrections. We first discuss the technical aspects of our approach, before confronting our predictions to those of existing public tools, performing a numerical analysis and discussing the remaining theoretical uncertainties. In particular, we find that the decay widths of doublet-dominated heavy Higgs bosons into electroweak gauge bosons are dominated by the radiative corrections, so that the tree-level approximations that are often employed in phenomenological analyses fail. Finally, we focus on the phenomenological properties of a mostly singlet-like state with a mass below the one at $125\,$GeV, a scenario that appears commonly within the NMSSM. In fact, the possible existence of a singlet-dominated state in the mass range around or just below $100\,$GeV would have interesting phenomenological implications. Such a scenario could provide an interpretation for both the $2.3\sigma$ local excess observed at LEP in the $e^+e^-\to Z(H\to b\bar{b})$ searches at $\sim 98\,$GeV and for the local excess in the diphoton searches recently reported by CMS in this mass range, while at the same time it would reduce the "Little Hierarchy" problem.