3 years ago

# Measurements of b -jet tagging efficiency with the ATLAS detector using t t ¯ $t\overline{t}$ events at s = 13 $\sqrt{s}=13$ TeV

### Abstract

The efficiency to identify jets containing b-hadrons (b-jets) is measured using a high purity sample of dileptonic top quark-antiquark pairs ( $$t\overline{t}$$ ) selected from the 36.1 fb−1 of data collected by the ATLAS detector in 2015 and 2016 from proton-proton collisions produced by the Large Hadron Collider at a centre-of-mass energy $$\sqrt{s}=13$$ TeV. Two methods are used to extract the efficiency from $$t\overline{t}$$ events, a combinatorial likelihood approach and a tag-and-probe method. A boosted decision tree, not using b-tagging information, is used to select events in which two b-jets are present, which reduces the dominant uncertainty in the modelling of the flavour of the jets. The efficiency is extracted for jets in a transverse momentum range from 20 to 300 GeV, with data-to-simulation scale factors calculated by comparing the efficiency measured using collision data to that predicted by the simulation. The two methods give compatible results, and achieve a similar level of precision, measuring data-to-simulation scale factors close to unity with uncertainties ranging from 2% to 12% depending on the jet transverse momentum.

DOI: 10.1007/JHEP08(2018)089

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