Speaker
Description
Light top quark superpartners are the key ingredients for supersymmetric models to solve the electroweak hierarchy problem. The compressed region of the parameter space that $m_{\tilde t_1} \approx m_{\chi^0_1}$ is notoriously difficult to search. In this region, if the LSP neutralino is pure bino, $\tilde t_1$ can be long-lived, which produces displaced vertices in detectors. We propose to use the monojet trigger plus the analysis of displaced vertices to cover this region. We apply this method to the 8 TeV CMS Open Data with a luminosity of 11.6~fb$^{-1}$, and find that using this method the $2\sigma$ limit of $m_{\tilde t}$ in the region $m_{\tilde t} - m_{\chi^0} \approx 15-30$ GeV is about $m_{\tilde t} > 350$ GeV.