B-tagging in CMS

The identification of b jets is a crucial issue to study and characterize various channels like top quark events and many new physics scenarios. Different b-tagging techniques are defined in CMS which benefit from the long life time, high mass and large momentum fraction of the b-hadron produced in b-quark jet. Effcient algorithms have been developed based on the measure of b-hadron secondary vertex or on tracks with a large impact parameter. Data collected in pp collisions at 7TeV in 2011 are used to estimate both the b-tagging effciency and the mistag rate from light flavor jets.