Resonant Higgs pair production as a probe of stop at the LHC

Abstract

Searching for top squark (stop) is a crucial task of the LHC. When the flavor conserving two body decays of the stop are kinematically forbidden, the stops produced near the threshold will live long enough to form bound states which subsequently decay through annihilation into the Standard Model (SM) final states. In the region of stop mixing angle $\theta_{\tilde{t}} \to 0$ or $\pi/2$, we note that the LHC-13 TeV diphoton resonance data can give a strong bound on the spin-$0$ stoponium ($\eta_{\tilde{t}}$) and exclude the constituent stop mass $m_{\tilde{t}}$ up to about 290 GeV. While in the large stop mixing region, the stoponium will dominantly decay to the Higgs pair. By analyzing the process $pp \to \eta_{\tilde{t}} \to h (\to b\bar{b} )h (\to \tau^+\tau^-)$, we find that a large portion of the parameter space on the $m_{\tilde{t}_1}$ - $\theta_{\tilde{t}}$ plane can be probed at $2\sigma$ significance level at the LHC with the luminosity ${\cal L}=3000$ fb$^{-1}$.