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

Understand

A search for the pair production of the lightest supersymmetric partner of the top quark ($\widetilde{\mathrm{t}}_1$) is presented.

• The search focuses on a compressed scenario where the mass difference between the top squark and the lightest supersymmetric particle, often considered to be the lightest neutralino ($\widetilde{\chi}^0_1$), is smaller than the mass of the W boson.
• The proton-proton collision data were recorded by the CMS experiment at a centre-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 35.9 fb$^{-1}$.
• In this search, two decay modes of the top squark are considered: a four-body decay into a bottom quark, two additional fermions, and a $\widetilde{\chi}^0_1$; and a decay via an intermediate chargino.