Supersymmetric Exotic Decays of the 125 GeV Higgs Boson

Abstract: We reveal a set of novel decay topologies for the 125 GeV Higgs boson in supersymmetry which are initiated by its decay into a pair of neutralinos, and discuss their collider search strategies. This category of exotic Higgs decays are characterized by the collider signature: visible objects + $\mbox{${\not! E}{\rm T}$}$, with $\mbox{${\not! E}{\rm T}$}$ dominantly arising from escaping dark matter particles. Their benchmark arises naturally in the Peccei-Quinn symmetry limit of the MSSM singlet-extensions, which is typified by the co-existence of three light particles: singlet-like scalar $h_1$ and pseudoscalar $a_1$, and singlino-like neutralino $\chi_1$, all with masses of $\lesssim 10$ GeV, and the generically suppression of the exotic decays of the 125 GeV Higgs boson $h_2\to h_1 h_1$, $a_1a_1$ and $\chi_1\chi_1$, however. As an illustration, we study the decay topology: $h_2 \to \chi_1 \chi_2$, where the bino-like $\chi_2$ decays to $h_1 \chi_1$ or $a_1 \chi_1$, and $h_1/a_1 \to f\bar f$, with $f\bar f = \mu^+\mu^-$, $b\bar b$. In the di-muon case ($m_{h_1/a_1} \sim 1$ GeV), a statistical sensitivity of $\frac{S}{\sqrt{B}} > 6 \sigma$ can be achieved easily at the 8 TeV LHC, assuming $\frac{\sigma(pp \rightarrow W h_2)}{\sigma(pp \rightarrow W h_{\rm SM})} {\rm Br}(h_2 \to \mu^+\mu^- \chi_1 \chi_1)=0.1$. In the $b\bar b$ case ($m_{h_1/a_1} \sim 45$ GeV), 600 fb$^{-1}$ data at the 14 TeV LHC can lead to a statistical sensitivity of $\frac{S}{\sqrt{B}} > 5 \sigma$, assuming $\frac{\sigma(pp \rightarrow Z h_2)}{\sigma(pp \rightarrow Z h_{\rm SM})} {\rm Br}(h_2 \to b\bar b \chi_1 \chi_1)=0.5$. These exotic decays open a new avenue for exploring new physics couplings with the 125 GeV Higgs boson at colliders.