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High Mass Drell Yan Differential Cross-section (ATLAS)

High Mass Drell Yan Differential Cross-section (ATLAS). Paul Bell University of Geneva on behalf of the high mass DY analysis team 18 / 2 / 2013. The measurement. Measurement of DY differential cross section in di -electron channel As function of di -electron invariant mass

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High Mass Drell Yan Differential Cross-section (ATLAS)

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  1. High Mass Drell Yan Differential Cross-section (ATLAS) Paul Bell University of Geneva on behalf of the high mass DY analysis team 18/2/2013

  2. The measurement • Measurement of DY differential cross section in di-electron channel • As function of di-electron invariant mass • In “high mass” region = 116 – 1500 GeV • Within “extended fiducial” region of electron pT > 25 GeV and | eta | < 2.5 • CONF note: • https://cds.cern.ch/record/1493623 • (paper in approval) • Main backgrounds: • W + jets & multijets where • jet fakes the electron ID • => data driven, 4 methods • Other backgrounds from MC

  3. “Unfolding” method • Fiducial cross section within extended fiducialregion given by • where CDYis the correction factor, given by where NMC,reco = sum of MC signal events after simulation and selection in measured fiducial region (excludes the “crack” region) NMC,gen-fid = sum of MC signal events at generator levelwithin extendedfiducial region i.e. CDY includes the small extrapolation over the crack region. Cross-section measured at different levels of QED FSR correction corresponding to different truth level definitions of NMC,gen-fid: • Born level: Using electrons before QED FSR, i.e. full QED correction • dressed level: Where 4-vectors of the bare lepton and allQED FSR photons within a cone of ∆R < 0.1 are resummed to perform a partial QED FSR correction

  4. Results and systematics • Statistical uncertainty dominates for • mee > 500 GeV • Reaches 50% in highest mee bin • Total systematic uncertainty within 10% • Dominated at low meeby electron efficiency and at high meeby background estimate

  5. Results: generator comparison • MC comparison at dressed level • MC predictions agree well in shape only, after scaling globally

  6. Results: FEWZ 3.1 comparison • FEWZ 3.1 comparison • at Born level with • recent NNLO PDFs • FEWZ allows (N)NLO • QCD corrections to be combined with the NLO electroweak corrections • Choice of EW scheme, Gµor α(MZ), at most 0.4% effect, after applying NLO electroweak corrections • Contribution fromphoton-induced (PI) background, evaluated at LO using MRST2004qed • Correction fromreal W/Z radiation evaluated using MADGRAPH 5, at most 2% at highest mee (not shown)

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