Abstract
The results of a search for a supersymmetric partner of the top quark (top squark), pair-produced in proton-proton collisions at sqrt(s) = 8 TeV, are presented. The search, which focuses on R-parity violating, chargino-mediated decays of the top squark, is performed in final states with low missing transverse momentum, two oppositely charged electrons or muons, and at least five jets. The analysis uses a data sample corresponding to an integrated luminosity of 19.7 inverse femtobarns collected with the CMS detector at the LHC in 2012. The data are found to be in agreement with the standard model expectation, and upper limits are placed on the top squark pair production cross section at 95% confidence level. Assuming a 100% branching fraction for the top squark decay chain, top squark to t + chargino, chargino to lepton + jj, top squark masses less than 890 (1000) GeV for the electron (muon) channel are excluded for the first time in models with a single nonzero R-parity violating coupling lambda'[ijk] (i,j,k <= 2), where i,j,k correspond to the three generations.
Highlights
Supersymmetry (SUSY) [1,2] is an extension of the standard model (SM) that may provide a solution to the hierarchy problem [3,4]
Searches for SUSY are performed in many decay channels and are classified into R-parity conserving (RPC) and R-parity violating (RPV) scenarios
The top squark pair production cross section is computed at NLO as a function of Mt, including soft gluon resummation at next-to-leading logarithm (NLL) [47,48,49,50]
Summary
Supersymmetry (SUSY) [1,2] is an extension of the standard model (SM) that may provide a solution to the hierarchy problem [3,4]. In RPC models the top squark is expected to decay into the lightest SUSY particle, which escapes detection. This results in an event signature with substantial missing transverse momentum. R-parity may not be conserved, in which case searches for SUSY particle decaying to SM particles without substantial missing transverse momentum are important. If baryon number and lepton number were both violated, proton decay would proceed at a rate excluded by experimental observations [14,15]. CMS Collaboration / Physics Letters B 760 (2016) 178–201 are two leptons (e± or μ±) and six jets, two of which are b-tagged jets
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