Combined measurement of the ttbar cross section and b tagging efficiency using mu+jets events

The Large Hadron Collider, build at CERN, is the first collider in the world able to act as a top quark factory. The large amounts of top quark events produced allow us to study the properties of this heavy quark in great detail. We propose a combined measurement of the $t{\bar t}$ cross section and the b-tagging efficiency using the muon+jets event topology observed by the CMS experiment in the 7 TeV proton collisions of the LHC. The data collected in 2011 used for this measurement corresponds to an integrated luminosity of 1.1 fb$^{-1}$. The obtained $t\bar t$ cross section is 177.8 $\pm$ 11.2 (stat.) $\pm$ 50.6 (syst.) $\pm$ 11.3 (lumi) pb together with a measured b-tagging efficiency of 60.3 $\pm$ 3.2 (stat.) $\pm$ 33.1 (syst.)\%. A $b$-tag algorithm based on the second highest 2D impact parameter significance among all tracks in the jet is applied with a threshold corresponding to a light-flavor mistagging rate of 1\%. The result of this crosscheck analysis is in agreement with the main CMS result of 164.4 $\pm$ 2.8 (stat.) $\pm$ 11.9 (syst.) $\pm$ 7.4 (lum.) pb obtained.