Invisible decays of low mass Higgs bosons in supersymmetric models

Abstract

The discovery of a 126 GeV Higgs-like scalar at the LHC along with the nonobservation of the supersymmetric particles has in turn led to constraining various supersymmetric models through the Higgs data. We here consider the case of both the minimal supersymmetric standard model (MSSM) as well its extension containing an additional chiral singlet superfield, the next-to-minimal or nonminimal supersymmetric standard model (NMSSM). A lot of work has been done in the context of the lightest scalar of these models being identified as the 126 GeV state discovered at the LHC. We here, however, concentrate on the case where we identify the second lightest Higgs boson as the 126 GeV state discovered at the CERN LHC and consider the invisible decays of the low mass Higgs bosons in both the MSSM and NMSSM. In the case of the MSSM we consider $H\ensuremath{\approx}126\text{ }\text{ }\mathrm{GeV}$ and $h\ensuremath{\approx}98\text{ }\text{ }\mathrm{GeV}$, known as the nondecoupling regime, whereas in the case of the NMSSM ${h}_{2}\ensuremath{\approx}126\text{ }\text{ }\mathrm{GeV}$, with ${m}_{{h}_{1}}$ and ${m}_{{a}_{1}}$ varying depending on the parameter space. We find that, in the case of the MSSM with universal boundary conditions at the grand unified theory (GUT) scale, it is not possible to have light neutralinos leading to the decay channel $H\ensuremath{\rightarrow}{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{0}{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{0}$. The invisible decay mode is allowed in the case of certain $SO(10)$ and ${E}_{6}$ grand unified models with large representations and nonuniversal gaugino masses at the GUT scale. In the case of the NMSSM, for the parameter space considered it is possible to have the invisible decay channel with universal gaugino masses at the GUT scale. We furthermore consider the most general case, with ${M}_{1}$ and ${M}_{2}$ as independent parameters for both the MSSM and NMSSM. We isolate the regions in parameter space in both cases where the second lightest Higgs boson has a mass of 126 GeV and then concentrate on the invisible decay of Higgs bosons to lighter neutralinos. The other nonstandard decay mode of the Higgs boson is also considered in detail. The invisible Higgs branching ratio being constrained by the LHC results, we find that, in this case with the second lightest Higgs boson being the 126 GeV state, more data from the LHC are required to constrain the neutralino parameter space, compared to the case when the lightest Higgs boson is the 126 GeV state.