Using machine learning to measure the cross section of top quark pairs in the muon+jets channel at the Compact Muon Solenoid

The cross section for pp → tt¯ production at a center of mass energy of 7 TeV is measured using a data sample with integrated luminosity 36.1 pb--1 collected by the CMS detector at the LHC. The analysis is performed on a computing grid. Events with an isolated muon and three hadronic jets are analyzed using a multivariate machine learning algorithm. Kinematic variables and b tags are provided as input to the algorithm; output from the algorithm is used in a maximum likelihood fit to determine tt¯ event yield. The measured cross section is 151 +/- 15 stat.+35-2 8 (syst.) +/- 6(lumi.) pb.