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SM WW->lνlν 4.7fb -1 analysis: Moriond results

SM WW->lνlν 4.7fb -1 analysis: Moriond results. Measurement of the WW production cross-section in the di-lepton (e,μ) final state Motivation: Important test of the electroweak sector of the Standard Model Irreduciable background for Higgs searches.

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SM WW->lνlν 4.7fb -1 analysis: Moriond results

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  1. SM WW->lνlν 4.7fb-1 analysis: Moriond results • Measurement of the WW production cross-section in the di-lepton (e,μ) final state • Motivation: • Important test of the electroweak sector of the Standard Model • Irreduciable background for Higgs searches. • Sensitive to anomalous triple gauge couplings • Updated to 1.02 fb-1 • Latest 4.7 fb-1results for Moriond EW 2012(support note, conf note, conf talk) • Update BOTH fiducial and inclusive cross-sections for full 2011 dataset • Working on optimization and including aTGC 4.7fb-1 updates. • 1fb-1 presented aTGC limits presented in Moriond qq->WW production σNLO = (43.8±2.25)pb at 7TeV gg->WW contributes additional ~3% of WW event rate: 1.3pb • Conf results quick summary: • Cross section precision ∼ 10…15% (largely systematic): ATLAS and CMS ∼ 1σ above NLO prediction • aTGC limits sensitive to high leading lepton pT : limits in between Tevatron and LEP

  2. WW background estimation: Wjets and Top • Wjet DD estimate: • Jets misidentified as leptons not correctly modeled and limited by stat. in MC • W+jets enriched control sample and fake factor measured in data • W+jets CR: nominal cuts w/ looser lepton ID for one of the 2 leptons • Fake factor: ratio of and looser (“jet-rich”) leptons • Cross-check of method in SS CR. • Top DD estimate using b-tagged control sample • P1: b-tagging control sample jet Veto survival probability • P2: full jet veto survival probability • Agree w/ MC prediction. • ~20.4% overall syst. Dominated by theo. Uncertainty~15% and sample dependence~12%

  3. WW background estimation: Drell-Yan and other DiBoson DY bgd: lepton or jet energy not well measured • The Etmiss,Rel not well modeled in DY MC, use a data-driven scale factor to correct for the Etmiss,rel cut efficiency. • Procedure: • Invert Z window veto, apply other nominal selection cuts • ee, μμ: S Factor • eμ: no Z cut, use MC prediction w/ syst. estimate from ee/μμ using same Etmiss,Rel cut value in eμ, corresponding difference quoted. Expected DiBoson Yields(purely MC prediction) Wγ* partially double counted in WZ, therefore scaled down in each channel based on ratio passing WZ gauge boson high mass cut

  4. Acceptance and Fiducial xsec Fiducial cross section measured in the phase space mimic the nominal selection Overall WW signal acceptance determined by MC The total WW production x-section is determined from 3 dilepton channels (ee, μμ and eμ) by maximising log-likelihood functions: Deviate from SM prediction -0.3σ +1.4σ +1.5σ +1.4σ

  5. On-going effort for 4.7fb-1 publication Truth deviation • Optimization I: track-based MET • Track MET supposedly less sensitive to pileup • Missing neutral part, larger DY tail less good resolution • expected to be a powerful weapon against DY contamination for WW SR. • Tested different MVA tech. • Combined w/ more discriminants • To be considered for 2012 analysis due to the time scale of publication • Optmization II: ptll and MC rescaling • Ptll cut combined with jet Veto will enhance the DY processes boosted by low Energy activities which can not be expected to be well modeled in MC • M(ll) line-shape scale factor to correct for the MC prediction of DY. Work to be discussed and finalized… Z-window distribution MVA performance • Drell-Yan CR def: • Etmiss,rel[5,30]GeV favored • Passing full-jet veto and ptll • Subtract all ther other background and signal Ptll cut eff rescale ee+μμ combined

  6. Spare

  7. Final WW candidate plotsapproved for Moriond MT(l+l-, Etmiss) leading pT subleading pT Δφ(l+l-) PT(l+l-) PT(l+l-, Etmiss)

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