Search for a scalar partner of the top quark in the jets plus missing transverse momentum final state at $\sqrt{s}=13$ TeV with the ATLAS detector

Abstract

A search for pair production of a scalar partner of the top quark in events with four or more jets plus missing transverse momentum is presented. An analysis of $36.1\,\mathrm{fb}^{-1}$ of $\sqrt{s}=13$ TeV proton-proton collisions collected using the ATLAS detector at the LHC yields no significant excess over the expected Standard Model background. To interpret the results a simplified supersymmetric model is used where the top squark is assumed to decay via $ {\tilde{t}}_1\to {t}^{\left(\ast \right)}{\tilde{\chi}}_1^0$ and ${\tilde{t}}_1\to b{\tilde{\chi}}_1^{\pm}\to b{W}^{\left(\ast \right)}{\tilde{\chi}}_1^0$, where $\tilde{\chi}_1^0$ ($\tilde{\chi}_1^\pm$) denotes the lightest neutralino (chargino). Exclusion limits are placed in terms of the top-squark and neutralino masses. Assuming a branching ratio of 100% to $t{\tilde{\chi}}_1^0$, top-squark masses in the range 450–1000 GeV are excluded for ${\tilde{\chi}}_1^0$ masses below 160 GeV. In the case where $m_{\tilde{t}}\sim m_t+m_{\tilde{\chi}_1^0}$, top-squark masses in the range 235–590 GeV are excluded.

Baptiste Ravina

Alexander von Humboldt Fellow

I’m an experimental particle physicist looking for new physics at the ATLAS experiment with machine learning.