ATLAS collaboration (2873 authors)Aguilar-Saavedra, Juan AntonioAmor Dos Santos, Susana PatriciaAnjos, NunoAraque, Juan PedroCarvalho, JoãoCastro, Nuno FilipeConde Muiño, PatriciaDa Cunha Sargedas De Sousa, Mario JoseFiolhais, MiguelGalhardo, BrunoGomes, AgostinhoGonçalo, RicardoJorge, PedroMachado Miguens, JoanaMaio, AméliaManeira, JoséOleiro Seabra, Luis FilipeOnofre, AntónioPedro, RuteSantos, HelenaSaraiva, JoãoSilva, JoséTavares Delgado, AdemarVeloso, FilipeWolters, Helmut2019-02-042019-02-042017-12-15http://dx.doi.org/10.1007/JHEP12(2017)085http://hdl.handle.net/10400.26/27439A 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$_{1}^{0}$ (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.engjournal article2019-02-04