Abstract
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. Efficient 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 √s = 7 TeV in 2011 are used to estimate both the b-tagging efficiency and the mistag rate from light flavor jets.
Highlights
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
The b-tagging algorithms in CMS mainly rely on the long life time, high mass and large momentum fraction of b hadrons produced in b-quark jets, as well as on the presence of soft leptons from semi-leptonic b decays[1]
The impact parameter significance IP/σ(IP) is used in order to take into account resolution effects.Thanks to the long lifetime of the b-hadrons the IP from b-jets is expected to be mainly positive, while for the light jets it is almost symmetric with respect to zero (Fig.4)
Summary
The b-tagging algorithms in CMS mainly rely on the long life time, high mass and large momentum fraction of b hadrons produced in b-quark jets, as well as on the presence of soft leptons from semi-leptonic b decays[1]. Due to the high instantaneous luminosity during the 2011 data taking, the number of collision taking place in the same bunch crossing (pileup events) is of the order of 5 to 11 on average. The transverse momentum of the muon relative to the jet direction. In the following a brief description of these variable is presented
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