Studies of jet mass in dijet and W/Z + jet events

Invariant mass spectra for jets reconstructed using the anti-k T and CambridgeAachen algorithms are studied for different jet grooming techniques in data corresponding to an integrated luminosity of 5 fb-1, recorded with the CMS detector in proton-proton collisions at the LHC at a center-of-mass energy of 7 TeV. Leading-order QCD predictions for inclusive dijet and W/Z+jet production combined with parton-shower Monte Carlo models are found to agree overall with the data, and the agreement improves with the implementation of jet grooming methods used to distinguish merged jets of large transverse momentum from softer QCD gluon radiation. © 2013 CERN for the benefit of the CMS collaboration.

Search for the standard model Higgs boson produced in association with a top-quark pair in pp collisions at the LHC

A search for the standard model Higgs boson produced in association with a top-quark pair is presented using data samples corresponding to an integrated luminosity of 5.0 fb-1 (5.1 fb-1) collected in pp collisions at the center-of-mass energy of 7 TeV (8 TeV). Events are considered where the top-quark pair decays to either one lepton+jets (tt̄ → ℓvqq̄bb̄) or dileptons (tt̄ → ℓ+vl- rfvn1̄bb̄), ℓ being an electron or a muon. The search is optimized for the decay mode H → bb̄. The largest background to the tt̄H signal is top-quark pair production with additional jets. Artificial neural networks are used to discriminate between signal and background events. Combining the results from the 7 TeV and 8 TeV samples, the observed (expected) limit on the cross section for Higgs boson production in association with top-quark pairs for a Higgs boson mass of 125 GeV is 5.8 (5.2) times the standard model expectation. [Figure not available: see fulltext.] © 2013 Cern for the benefit of the CMS collaboration.

Search for physics beyond the standard model in events with τ leptons, jets, and large transverse momentum imbalance in pp collisions at √s = 7 TeV

A search for physics beyond the standard model is performed with events having one or more hadronically decaying τ leptons, highly energetic jets, and large transverse momentum imbalance. The data sample corresponds to an integrated luminosity of 4.98 fb-1 of proton-proton collisions at √ = 7 TeV collected with the CMS detector at the LHC in 2011. The number of observed events is consistent with predictions for standard model processes. Lower limits on the mass of the gluino in supersymmetric models are determined. © 2013 CERN for the benefit of the CMS collaboration.

Measurement of masses in the tt̄ system by kinematic endpoints in pp collisions at √s = 7 TeV

A simultaneous measurement of the top-quark, W-boson, and neutrino masses is reported for tt̄ events selected in the dilepton final state from a data sample corresponding to an integrated luminosity of 5.0 fb-1 collected by the CMS experiment in pp collisions at √s = 7 TeV. The analysis is based on endpoint determinations in kinematic distributions. When the neutrino and W-boson masses are constrained to their world-average values, a top-quark mass value of Mt = 173.9 ± 0.9 (stat)+1.7 -2.1(syst.) GeV is obtained. When such constraints are not used, the three particle masses are obtained in a simultaneous fit. In this unconstrained mode the study serves as a test of mass determination methods that may be used in beyond standard model physics scenarios where several masses in a decay chain may be unknown and undetected particles lead to underconstrained kinematics. © 2013 CERN for the benefit of the CMS collaboration.