Simultaneous enhancement inγγ,bb¯andτ+τ−rates in the NMSSM with nearly degenerate scalar and pseudoscalar Higgs bosons

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We propose an experimental test of a scenario in the next-to-minimal supersymmetric standard model in which both the lightest scalar and the lightest pseudoscalar Higgs bosons have masses around 125 GeV. The pseudoscalar can contribute significantly to the $\ensuremath{\gamma}\ensuremath{\gamma}$ rate at the LHC due to light Higgsino-like charginos in its effective one-loop coupling to two photons. Such charginos are obtained for small values of the ${\ensuremath{\mu}}_{\mathrm{eff}}$ parameter, which also results in enhanced $b\overline{b}$ and ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ rates compared to those expected for a standard model (SM) Higgs boson. This scenario should result in a clear discrepancy between the observed rates in these three decay channels and those in the $WW$ and $ZZ$ channels, since the pseudoscalar does not couple to the $W$ and $Z$ bosons. However, in the dominant gluon fusion production mode, the pseudoscalar will stay hidden behind the SM-like scalar Higgs boson, and in order for it to be observable, the associated $b\overline{b}h$ production mode has to be considered, the cross section for which is tiny in the SM but $\mathrm{tan}\ensuremath{\beta}$-enhanced in supersymmetry. We analyze the constrained next-to-minimal supersymmetric standard model with nonuniversal Higgs sector parameters and identify regions of its parameter space where the lightest pseudoscalar with mass around 125 GeV and strongly enhanced $\ensuremath{\gamma}\ensuremath{\gamma}$ (up to 60%), $b\overline{b}$ and ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ rates in the $b\overline{b}h$ mode can be obtained.