Identification of b-quark jets with the CMS experiment

• Published in: Journal of instrumentation 2013-04, Vol.8 (4), p.1-65
• Main Authors: Chatrchyan, S, Khachatryan, V, Sirunyan, A M, Tumasyan, A, Adam, W, Aguilo, E, Bergauer, T, Dragicevic, M, Ero, J, Fabjan, C, Friedl, M, Fruhwirth, R, Ghete, V M, Hammer, J
• Format: Article
• Language: English
• Subjects: Algorithms; Decay; High Energy Physics - Experiment; Instrumentation; Jets; Large Hadron Collider; Luminosity; Marking; Mathematical models; Physics; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
• ISSN: 1748-0221; 1748-0221
• DOI: 10.1088/1748-0221/8/04/P04013

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 square root s = 7TeV for a total integrated luminosity of 5.0 fb super(-1). 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.