Abstract
A search for the pair production of the lightest supersymmetric partner of the top quark left({tilde{mathrm{t}}}_1right) 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 left({tilde{upchi}}_1^0right) , 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 {tilde{upchi}}_1^0 ; and a decay via an intermediate chargino. Events are selected using the presence of a high-momentum jet, significant missing transverse momentum, and a low transverse momentum electron or muon. Two analysis techniques are used, targeting different decay modes of the {tilde{mathrm{t}}}_1 : a sequential selection and a multivariate technique. No evidence for the production of top squarks is found, and mass limits at 95% confidence level are set that reach up to 560 GeV, depending on the mleft({tilde{mathrm{t}}}_1right)-mleft({tilde{upchi}}_1^0right) mass difference and the decay mode.
Highlights
Detector and object definitionThe central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T
Background predictionThe dominant backgrounds in most of the CC signal regions are W+jets and tt production with a prompt lepton in the final state
After performing the two searches, we find no evidence for direct top squark production, as can be seen in table 5 and in figure 6 for the multivariate analysis (MVA) and CC searches, respectively
Summary
The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. This analysis utilizes the CMS particle-flow (PF) algorithm [23] to reconstruct and identify PF candidates such as leptons (electrons and muons), photons, and charged and neutral hadrons. The physics objects are the jets, clustered using a jet finding algorithm [24, 25] with the tracks assigned to the vertex as inputs, and the associated missing transverse momentum, taken as the negative vector sum of the pT of those jets. The electrons and muons are required to satisfy Iabs < 5 GeV for pT( ) < 25 GeV and Irel < 0.2 for pT( ) > 25 GeV This combined isolation criterion allows for a more uniform selection efficiency of leptons as a function of lepton pT. The same figures for the loose working point, which is used in the MVA search, are 10% and 80%, respectively
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
