Search for a Scalar Partner of the Top Quark in the Jets Plus Missing Transverse Momentum Final State at √s = 13 TeV with the ATLAS Detector

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 √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 t˜₁ → t(()) χ˜₁⁰ and t˜₁ → bχ˜ (±)(1) → bW(()) χ˜₁⁰, where χ˜₁⁰ (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 tχ˜₁⁰ top-squark masses in the range 450-1000 GeV are excluded for χ˜₁⁰ masses below 160 GeV. In the case where m(t˜)₁ ~ m(t) + m(χ˜₁⁰), top-squark masses in the range 235-590 GeV are excluded.