Search for top squarks decaying via four-body or chargino-mediated modes in single-lepton final states in proton-proton collisions at $\sqrt{s} =$ 13 TeV

the Marie-Curie programme and the European Research Council and Horizon 2020 Grant (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation `a la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS and FWO (Belgium) under the “Excellence of Science — EOS” — be.h project n. the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Lendu¨let (“Momentum”) Programme and the J´anos Bolyai Research Scholarship of the Hungarian Academy of Sciences, the New National Excellence Program ´UNKP, the NKFIA research grants (Hungary); the Council of Science and Industrial Researchndia; the HOMING PLUS programme of the Foundation for Polish Science, cofinanced from European Union, Regional Development Fund, the Mobility Plus programme of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts Harmonia Opus 1, Sonata-bisthe National Priorities Research Program by Qatar National Research Fund; the Programa Estatal de Fomento de la Investigaci´on Cient´ifica y T´ecnica de Excelencia Mar´ia de Maeztu, grant MDM and the Programa Severo Ochoa del Principado de Asturias; the Thalis and Aristeia programmes cofinanced by EU-ESF and the Greek NSRF; the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); the Welch Foundation, contract ; and the Weston Havens Foundation (U.S.A.).