Measurement of the ratio of inclusive cross sections sigma(pp going to Z+b-jet)/sigma(pp going to Z+jet) in the dilepton final states
Smith, Kenneth James
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The inclusive production of b -jets with a Z boson is an important background to searches for the Higgs boson in associated ZH → llbb ̄ production at the Fermilab Tevatron collider. This thesis describes the most precise measurement to date of the ratio of inclusive cross sections σ( pp ̄ → Z + b -jet)/σ( pp ̄ → Z +jet) when a Z boson decays into two electrons or muons. The measurement uses a data sample from pp ̄ collisions at the center of mass energy [special characters omitted] = 1.96 TeV corresponding to an integrated luminosity of 4.2 fb −1 collected by the D0 detector. The measured ratio σ( Z + b -jet)/σ( Z +jet) is 0.0187 ± 0.0021( stat ) ± 0.0015( syst ) for jets with transverse momentum p T > 20 GeV and pseudorapidity |η| ≤2.5. The measurement is compared with the next-to-leading order theoretical predictions from MCFM and is found to be consistent within uncertainties.