Performance of $b$-Jet Identification in the ATLAS Experiment

TL;DR

This paper evaluates and calibrates various algorithms for identifying $b$-jets in the ATLAS experiment, providing efficiency measurements and scale factors to improve $b$-jet tagging accuracy in collider data analysis.

Contribution

It introduces and compares multiple $b$-jet tagging algorithms, including new methods based on muon reconstruction and online trigger, and provides calibration results for data-simulation scale factors.

Findings

$b$-jet tagging efficiency measured with multiple methods

Calibration scale factors for $b$, $c$, and light-flavor jets provided

Combined calibration results account for correlations and systematic uncertainties

Abstract

The identification of jets containing $b$ hadrons is important for the physics programme of the ATLAS experiment at the Large Hadron Collider. Several algorithms to identify jets containing $b$ hadrons are described, ranging from those based on the reconstruction of an inclusive secondary vertex or the presence of tracks with large impact parameters to combined tagging algorithms making use of multi-variate discriminants. An independent $b$-tagging algorithm based on the reconstruction of muons inside jets as well as the $b$-tagging algorithm used in the online trigger are also presented.The $b$-jet tagging efficiency, the $c$-jet tagging efficiency and the mistag rate for light flavour jets in data have been measured with a number of complementary methods. The calibration results are presented as scale factors defined as the ratio of the efficiency (or mistag rate) in data to that in simulation. In the case of $b$ jets, where more than one calibration method exists, the results from the various analyses have been combined taking into account the statistical correlation as well as the correlation of the sources of systematic uncertainty.