1. Dimuon Channel ( Z  μμ ) L uminosity ~180 pb -1 (recorded) 2 isolated muons with both having matching central tracks |η μ | 15 GeV 65.0 < M μ 1 μ 2 < 115.0 GeV Systematic Uncertainties Measurement of the Ratio of Inclusive Cross Sections σ(pp → Z+b)/σ(pp → Z+j) Measurement of the Ratio of Inclusive Cross Sections σ(pp  Z+b)/σ(pp  Z+j) at DØ RunII Abstract We study the b-jet production in association with the Z boson at DØ, using Run II data collected between August'02 and September'03 corresponding to about 180 pb^-1 of recorded luminosity. In this study, we also present a measurement of the ratio of cross sections of Z+bjet to Z+jet inclusive production. Yıldırım D. Mutaf SUNY at Stony Brook (on behalf of DØ Collaboration) DØ Detector & Run II Multi-purpose Collider Detector at FNAL 1.96 TeV proton/anti-proton collisions New Tracking System (including a silicon vertex and central fiber tracking detector) & 2T magnet New Central/Forward PreShower Detectors Upgrade Calorimeter Electronics & Muon System Improvements New Trigger System Data Sample & Event Selection The analysis is performed in two channels as characterized by the decays of the Z boson: Dielectron Channel ( Z  ee ) L uminosity ~184 pb -1 2 isolated electrons with at least 1 track match |η e | 15 GeV 80.0 < M e 1 e 2 < 100.0 GeV Z  ee Z  μμ Jet Selection & B-tagging Calorimeter cone jets, R=0.5 |η j | 20 GeV Taggability requirement Calorimeter jets are required to have matching tracks for taggability B-tag the jets with reconstructed Secondary Vertices, δR < 0.5 DØ Run-II Preliminary Methodology & Selected Events Zb ZcZq R ≡ pp Zb ZcZqBckg ZbZcZqBckg ZbZcZqB Z+jet Z+taggable jet Z+btagged jet Analysis Z + taggable jet & btagged jet events Z  μμ Z  ee Z  μμ Dilepton Mass (≥1 btagged jets)Taggable Jet p T (GeV/c) Selected Z Event Counts Systematics & Results LEFT : Taggable jet transverse momentum spectrum.The data (points) with jet-energy-scale errors (shades over points) are compared to ALPGEN Z+j MC (open histogram) and overlayed with expected background contribution (dark fill histogram.) RIGHT : Dimuon mass distribution for b-tagged jet events. Shown for data events alone without the invariant mass cut. The dielectron & dimuon channels are combined statistically to obtain the final result: R = 0.024  0.005(stat) (syst) Consistent with theoretical calculation of ~0.020 †. † J. M. Campbell, R. K. Ellis, F.Maltoni and S.Willenbrock, Phys. Rev. D69 (2004) 074021 Calculating the Background Contributions The multijet (mostly bbbar) background is calculated from data using the inefficiency of the isolation requirement as the major characteristic for this type of background. The mistag(light jet tagging) rate is extracted from jet triggered data For the charm contribution, SV’s don’t provide a distinction between b & c type of quarks so we used MC charm tagging efficiency and scale this efficiency to what we expect in data The b/c data composition ratio is obtained from theoretical calculations †. (μμ) (μμ+ee) + 0.005 - 0.004 The secondary vertex (SV) decay length significance plot along with track multiplicity and b-tagged jet momentum plots shows the heavy quark domination in the tagged sample (Z+btagged jet). Taggability SV Tagging Z  ee