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Measurement of the Z/gamma* + b-jet cross section in pp collisions at 7 TeV

CMS Collaboration

Abstract

The production of b jets in association with a Z/gamma* 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/gamma* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross section with Z/gamma* to ll (where ll = ee or mu mu) for events with the invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.) +(0.25)/-(0.55) (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.

Measurement of the Z/gamma* + b-jet cross section in pp collisions at 7 TeV

Abstract

The production of b jets in association with a Z/gamma* 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/gamma* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross section with Z/gamma* to ll (where ll = ee or mu mu) for events with the invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.) +(0.25)/-(0.55) (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.

Paper Structure

This paper contains 1 section, 1 equation, 4 figures, 2 tables.

Table of Contents

  1. The CMS Collaboration

Figures (4)

  • Figure 1: Left: number of three-track secondary vertices per jet in dilepton+jet events. Right: SSV HP discriminant for the leading jet after the dilepton+jet selection. The yellow bands in the lower plots represent the statistical uncertainty on the MC yield.
  • Figure 2: Invariant mass (left) and $p_{\mathrm{T}}$ (right) of the lepton pairs after the dilepton+b-jet selection. The yellow bands in the lower plots represent the statistical uncertainty on the MC yield.
  • Figure 3: Left: $p_{\mathrm{T}}$ of the leading-$p_{\mathrm{T}}$ b jet after the dilepton+b-jet selection. Right: distribution of $\Delta \phi$(Z, b jet) between the leading-$p_{\mathrm{T}}$ b jet and the lepton pair after the dilepton+b-jet selection. The yellow bands in the lower plots represent the statistical uncertainty on the MC yield.
  • Figure 4: Secondary-vertex mass of the leading-$p_{\mathrm{T}}$ b jet, with MC distributions constructed from inclusive jet samples, for the dielectron (left) and dimuon (right) channels, after the b-purity maximum-likelihood fit.