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First observation of Z+b process at LHC

CP3 members contributed another prime measurement at LHC, with the early observation of the Z+b process at LHC. For the first time, the Z+bb candidates are also presented. This preliminary result is being shown at "Moriond 2011", the most important Winter conference in High Energy Physics.
By Christophe Delaere on March 22, 2011
Additional information:

Events coming from the associated production of the Z boson with at least one bottom-quark jet are studied using proton-proton collisions delivered by the LHC at a centre of mass energy of 7 TeV and recorded by the CMS detector in 2010. The selection of a final state with two leptons, electrons or muons, from the Z, and an additional b-tagged jet is described. The event yield and shapes of kinematic variables in 36 pb−1 of data recorded by CMS using single lepton triggers are compared with Monte Carlo predictions from MADGRAPH. In the data sample, 29 (36) events pass the dielectron (dimuon) and high-purity based b-tagging selections, with a measured purity of 0.83 0.10 of Z+b events. For the same b-tagging selection, the ratio σ( Z +b) is found to be 0.054 0.016 (0.046 0.014) in the data for the Z→ ee (Z→ ) σ( Z + j) selection, compared to 0.043 0.005 (0.047 0.005) estimated from NLO theory predictions with the same kinematic selections on the leptons and jets than the selections applied to the data.

Reference url: http://cms-physics.web.cern.ch/cms-physics/public/EWK-10-015-pas.pdf

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