Identification of b-quark jets with the CMS experiment

TL;DR

This paper presents the development and performance measurement of algorithms by CMS for identifying b-quark jets at the LHC, crucial for new physics searches and standard model measurements.

Contribution

It introduces and evaluates multiple b-jet tagging algorithms based on impact parameters, decay vertices, and leptons, with performance metrics from real collision data.

Findings

Achieved 85% b-jet tagging efficiency with 10% light-parton misidentification.

Achieved 70% b-jet tagging efficiency with 1.5% misidentification for higher purity.

Validated algorithm performance with 2011 LHC data at 7 TeV.

Abstract

At the Large Hadron Collider, the identification of jets originating from b quarks is important for searches for new physics and for measurements of standard model processes. A variety of algorithms has been developed by CMS to select b-quark jets based on variables such as the impact parameters of charged-particle tracks, the properties of reconstructed decay vertices, and the presence or absence of a lepton, or combinations thereof. The performance of these algorithms has been measured using data from proton-proton collisions at the LHC and compared with expectations based on simulation. The data used in this study were recorded in 2011 at sqrt(s) = 7 TeV for a total integrated luminosity of 5.0 inverse femtobarns. The efficiency for tagging b-quark jets has been measured in events from multijet and t-quark pair production. CMS has achieved a b-jet tagging efficiency of 85% for a light-parton misidentification probability of 10% in multijet events. For analyses requiring higher purity, a misidentification probability of only 1.5% has been achieved, for a 70% b-jet tagging efficiency.