Measuring the b-jet tagging efficiency using samples of jets containing muons with ATLAS data

The identification of jets originating from b-quarks, referred to as b-tagging, is an important part of the LHC physics program. In precision measurements in the top quark sector as well as in the search for the Higgs boson and new phenomena, the suppression of background processes containing predominantly light-flavour jets using b-tagging is of great use. In order for b-tagging to be used in physics analyses the efficiency with which a jet originating from a b-quark is tagged by a b-tagging algorithm needs to be measured. The b-tag efficiency can measured with two complementary methods in a sample of jets containing muons by exploiting the transverse momentum of the muon with respect to the jet axis (pTrel). One method fits pTrel templates to the data to extract the fraction of b-jets in the sample before and after b-tagging while the other method makes use of two samples with different flavour composition and two uncorrelated b-tagging algorithms.