Search for a Scalar Partner of the Top Quark in the Jets+ETmiss Final State at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search for direct pair production of a scalar partner to the top quark in events with four or more jets plus missing transverse momentum is presented. An analysis of 36 $\rm{fb^{-1}}$ of $\sqrt{s}=13$ TeV proton--proton collisions collected using the ATLAS detector at the LHC yielded no significant excess over the Standard Model background expectation. To interpret the results a supersymmetric model is used where the top squark is assumed to decay via $\tilde{t} \rightarrow t^{(*)} \tilde{\chi}^0_1$, where $\tilde{\chi}^0_1$ denotes the lightest neutralino. Exclusion limits are placed in terms of the top squark and neutralino masses. Assuming branching fractions of 100% to $t \tilde{\chi}^0_1$, top squark masses in the range 450-950 GeV are excluded for $\tilde{\chi}^0_1$ masses below 160 GeV. In the case where $m_{\tilde{t}}\sim m_t+m_{\tilde{\chi}^0_1}$ top squark masses between 235-590 GeV are excluded.