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 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 ${\tilde{t}}_1\to {t}^{\left(\ast \right)}{\tilde{\upchi}}_1^0$ and ${\tilde{t}}_1\to b{\tilde{\upchi}}_1^{\pm}\to b{W}^{\left(\ast \right)}{\tilde{\upchi}}_1^0$, where χ ⁰₁ (χ ^±₁ ) 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 $t{\tilde{\upchi}}_1^0$, top-squark masses in the range 450–1000 GeV are excluded for ${\tilde{\upchi}}_1^0$ masses below 160 GeV. In the case where ${m}_{{\tilde{t}}_1}\sim {m}_t+{m}_{{\tilde{\chi}}_1^0}$, top-squark masses in the range 235–590 GeV are excluded.