Abstract
Abstract The production of b jets in association with a Z/γ* boson is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV and recorded by the CMS detector. The inclusive cross section for Z/γ* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 fb−1. The Z/γ* + b-jet cross section with Z/γ* → ℓℓ (where ℓℓ = ee or μμ) for events with the invariant mass 60 < M ℓℓ < 120 GeV, at least one b jet at the hadron level with p T > 25 GeV and |η| < 2.1, and a separation between the leptons and the jets of ΔR > 0.5 is found to be $ {5}.{84}\pm 0.0{8}\left( {{\text{stat}}.} \right)\pm 0.{72}\left( {{\text{syst}}.} \right)_{ - 0.55}^{ + 0.25} $ (theory) pb. The kinematic properties of the events are also studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by pythia.
Highlights
At the Large Hadron Collider (LHC), the measurement of the production of a Z/γ∗ boson in association with b quarks is important, both as a benchmark channel to the production of the Higgs boson in association with b quarks, and as a standard model background for searches for the Higgs boson and new physics in final states with leptons and b jets
The kinematic properties of the events are studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by pythia
This paper describes the measurement with the Compact Muon Solenoid (CMS) detector of the pp → Z/γ∗+ b-jet cross section with Z/γ∗ →, including at least one b jet and any additional light jets, and compares it with theoretical predictions in the variable-flavour scheme
Summary
Tion of the three-dimensional flight distance significance from the reference primary vertex (i.e. the primary vertex with the highest quadratic sum of the pT of its constituent tracks, tracks p2T) to the chosen secondary vertex. The cross section for the production of a Z/γ∗ boson in association with at least one hadron-level b jet is extracted from the selected numbers of dielectron+b-jet and dimuon+b-jet events, taking into account the b-jet purity P, the fraction fttof ttevents, the b-tagging efficiency εb, the lepton efficiency ε , the correction factor Chadron for detector and reconstruction effects, and the lepton acceptance A , using the following equation: σhadron(Z/γ∗ + b, Z/γ∗ → It is defined with the following requirements: (i) pbT > 25 GeV and |ηb| < 2.1 on any hadron jet containing a b hadron, (ii) 60 < M < 120 GeV, and (iii) ∆R(jet, leptons) > 0.5. The systematic uncertainty on the ttcontribution is dominated by the uncertainty on the data/MC scale factor obtained with the dileptonic ttdecay measurement
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