b-Jet Identification in CMS

A large fraction of the CMS physics program relies on the identification of jets containing the decay of a B hadron (b jets). The b jets can be discriminated from jets produced by the hadronization of light quarks based on characteristic properties of B hadrons, such as the long lifetime or the presence of soft leptons produced during their decay.An overview of the large variety of b-tagging algorithms and the measurement of their performance with data collected in 2011 and 2012 are presented in this talk. A special focus lies on new methods of b-tagging in jet substructure.As the excluded mass regions for new physics beyond the Standard Model continue to increase, searches often focus on boosted final states characterized by particles with large transverse momenta. In the boosted regime the resulting decay products for hadronic decays of heavy particles tend to be collimated and can fall within a single jet, known as fat-jet. In this case, selections based on multiple jets cannot be applied and jet substructure is necessary to identify (tag) the particle initiating the jet. Substructure methods can be significantly improved by the identification of jets originating from bottom quarks (b-jets). This talk presents recent developments from the CMS collaboration in commissioning b-tagging algorithms in boosted topologies, both on fat-jets and on their subjets. A particular challenge is the measurement of the b-tagging performance in these topologies.