Search for top squark pair production in final states with one isolated lepton, jets and missing transverse momentum in √s = 8 TeV pp collisions using 21 fb^−1 of ATLAS data

The ATLAS Collaboration has performed a search for natural weak scale Supersymmetry (SUSY) in the form of light top quark partners (top squarks). Signal regions are optimized separately for the $\tilde{t}\mapsto t+\tilde{\chi}^0_1$ and $\tilde{t}\mapsto b+\tilde{\chi}^\pm_1$ decays. To increase the sensitivity of the search near the compressed scenario in which $m_{\text{top squark}}$ is only slightly more massive than $m_t+m_{\tilde{\chi}^0_1}$, a two-dimensional shape fit is performed in the missing momentum and transverse mass plane. No excess over the background is observed and limits are set on top squark pair production. For example, assuming the top squark decays only into a top quark and the lightest neutralino, top squark masses between 200 and 610 GeV are excluded at the 95% confidence level for a massless neutralino.