Calibrating the $b$-Tag and Mistag Efficiencies of the SV0 $b$-Tagging Algorithm in 3~pb$^{-1}$ of Data with the ATLAS Detector

The $b$-tag and mistag efficiencies of the secondary vertex $b$-tagging algorithm (SV0) have been measured on data. The $b$-tag efficiency measurement is based on a sample of jets containing muons and makes use of the transverse momentum of a muon relative to the jet axis (ptrel). The measurement of the mistag efficiency is performed on an inclusive jet sample and includes two methods, one which uses the invariant mass spectrum of tracks associated to reconstructed secondary vertices to separate light- and heavy-flavour jets and one which is based on the rate at which secondary vertices with negative decay length significance are present in the data. Both the $b$-tag and mistag efficiencies measured in data depend strongly on the jet kinematics. In the range $25 < p_T < 85$~GeV, the $b$-tag efficiency rises from 40% to 60%, while the mistag efficiency increases from 0.2% to 1% between 20 and 150~GeV. The measurements of the $b$-tag and mistag efficiencies are provided in the form of $p_T$-dependent scale factors correcting the $b$-tagging performance in simulation to that observed in data. For the $b$-tag efficiency, the scale factor is close to one for all values of jet $p_T$. The relative statistical (systematic) uncertainties range from 3% to 10% (10% to 12%). For light-flavour jets, the simulation underestimates the tagging efficiency by factors of $1.27 pm 0.26$ for jets with $p_T < 40 gev$ and $1.07 pm 0.25$ for jets with $p_T > 40 gev$.