FPO - Kelvin Mei - "A Search for Scalar Top Quarks in Final States with High Jet Multiplicity and a Lepton with the CMS detector at the Large Hadron Collider"

Mon, Aug 31, 2020, 3:30 pm
Location: 
Zoom Meeting ID: 986 6355 0604 Pswd 775644

A search is conducted for scalar top quarks decaying in the Full Run II dataset for the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) of 137.2\fbinv collected at a center of mass energy of √s = 14 TeV. The particular models being investigated involve pair production of scalar top quarks decaying either through an R-parity violating coupling or through a stealth sector into high jet multiplicity final states with low missing transverse energy. Novel machine-learning techniques have been applied, including gradient reversal, to extend sensitivity to a previously inaccessible and unexplored region of phase space. The highest observed local significance for the signal models investigated is 2.78 for the R-parity violating SUSY model where the scalar top quark mass is 400 GeV, with a local p value at 2.7 × 〖10〗^(-3) and a signal strength of 0.21± 0.07 times the theoretical predicated cross section. Limits are set at the 95% confidence level for the R-parity violating models with the scalar top quark mass less than 675 GeV and for stealth SUSY models with the scalar top quark mass less than 975 GeV.