Invisible decays of the lightest Higgs boson in supersymmetric models

Understand

We consider supersymmetric models in which the lightest Higgs scalar can decay invisibly consistent with the constraints on the $126$~GeV state discovered at the CERN LHC.

• We consider the invisible decay in the minimal supersymmetric standard model~(MSSM), as well its extension containing an additional chiral singlet superfield, the so-called next-to-minimal or nonminimal supersymmetric standard model~(NMSSM).We consider the case of MSSM with both universal as well as nonuniversal gaugino masses at the grand unified scale, and find that only an $E_6$ grand unified model with unnaturally large representation can give rise to sufficiently light neutralinos which can possibly lead to the invisible decay $h^0 \rightarrow \tilde \chi_1^0 \tilde \chi_1^0$.
• Following this, we consider the case of NMSSM in detail, where also we find that it is not possible to have the invisible decay of the lightest Higgs scalar with universal gaugino masses at the grand unified scale.
• We delineate the regions of the NMSSM parameter space where it is possible to have the lightest Higgs boson to have a mass of about $126$ GeV, and then concentrate on the region where this Higgs can decay into light neutralinos, with the soft gaugino masses $M_1$ and $M_2$ as two independent parameters, unconstrained by grand unification.