Drell-Yan Activities for the EWK Group Dimitri Bourilkov University of Florida LPC Di-lepton Meeting, FNAL, March 27, 2008

D.BourilkovDrell-Yan Activities for the EWK Group2 Introduction LHC is a high mass di-lepton factory Already with ~100 pb -1 we will be probing 800+ GeV Be ready to move to high masses immediately after demonstrating the Z peak performance

D.BourilkovDrell-Yan Activities for the EWK Group3 Drell-Yan Task Scope: study ee, μμ, e μ above (at startup – also below) the Z peak; ? Measure cross sections and (later) A FB Existing work: Use results from W/Z ee and μμ groups as a baseline; augment with high mass studies from HEEP and TeVmu groups For pb -1 extrapolation to higher masses will require MC and (to limited extent due to low event rates) data driven methods. Use ratios where possible. The residual dependence on p T and mass will need simulation inputs Combining ee and μμ (and e μ ) results - vital crosschecks: >cross sections should be ~ equal >same for DY mass spectra (slope), ratios to Z, etc.; as the resolutions for ee and μμ have opposite p T dependence, this will provide an important handle >A Z, below Z GeV should be ~equal

D.BourilkovDrell-Yan Activities for the EWK Group4 Efficiencies & Resolutions Efficiencies from data: tag and probe At Z: >trigger efficiencies >offline efficiencies Higher mass: >can not go higher than <~ GeV for 100 pb -1 due to limited statistics >backgrounds can be difficult Resolutions from data (p T, mass): Fit Z mass spectrum: advanced Momentum scale calibration High mass: limited statistics, no peak; p T balancing for μ + μ - ?!; leapfrog method for e + e - – how far can we go for lumi < 1fb -1 ?

D.BourilkovDrell-Yan Activities for the EWK Group5 Backgrounds MC studies progressing well (CSA07 soups) Data driven methods for jet-jet backgrounds (for ee, μμ ) Electrons: machine background? Muons: cosmics: studies underway machine background: >beam halo >neutrons? need more study

Chowder: (/CSA07Muon/CMSSW_1_6_7-CSA07-Tier0-A4-Chowder/AODSIM) tt+jets (up to 4 jets). W+jets (up to 5 jets). Z/gamma*+jets (up to 5 jets) not used in this study because of an upper mass cut. Stew: (/CSA07Muon/CMSSW_1_6_7-CSA07-Tier0-AOD-A01-Stew/AODSIM) BtoJpsi QCD_Pt_0_15 Charmonium Bottomonium Electron_ppEleX Muon_ppMuX Gumbo: (/CSA07Muon/CMSSW_1_6_7-CSA07-Tier0-A1-Gumbo/RECO) "Hard" QCD dijets (p T _hat >15 GeV) Minimum bias Gamma+jets WW, WZ, ZZ: /WW_incl/CMSSW_1_6_7-CSA /AODSIM /WZ_incl/CMSSW_1_6_7-CSA /AODSIM /ZZ_incl/CMSSW_1_6_7-CSA /AODSIM Compare results with the Drell-Yan background and Z′ signal. Use CSA07 background samples ( Studies of non-Drell-Yan backgrounds 1.Run over all events in these datasets. 2.Use CSA07EventWeightProducer (v ) to get weights for 100 pb −1. 3.Require OR of non-isolated single-muon and dimuon triggers. 4.Require two muons with M μμ > 400 GeV. Mingshui Chen (Beijing), Univ. of Florida

Dijet contribution is ~ as big as Drell- Yan in opp.-sign sample, and dominates same-sign. Two large-weight events from μX: b- bbar with p=30 TeV, and c-cbar with very poor χ 2 /dof (no quality cuts applied yet). Dimuon mass spectra w/o isolation cut Opposite sign Same sign Without isolation cut (and p T > 20 GeV cut): M. Chen (Beijing), Univ. of Florida

Require Σp T (in a cone of ΔR=0.3) < 10 GeV. QCD background is suppressed by an order of magnitude. Signal (and Drell-Yan) efficiency go down by 1-2%. Events rejected by the cut (as well as same-sign events before the cut) can be used to study QCD background. Isolation cut M. Chen (Beijing), Univ. of Florida Efficiency as a function of a Σp T (in a cone of ΔR=0.3) cutoff: PAS

Dijet contribution is very small. Largest non-Drell-Yan background is > 400 GeV, t-tbar (about ¼ of Drell- Yan). > 1 TeV, W+jets. Not enough stat. to conclude on b-bbar and c-cbar. Dimuon mass spectra w/ isolation cut Same sign Apply isolation cut (and p T > 20 GeV cut): M. Chen (Beijing), Univ. of Florida Opposite sign PAS

D.BourilkovDrell-Yan Activities for the EWK Group10 Theory / Monte Carlo Many things in common for ee and μμ PDF uncertainties: well advanced QCD corrections: results with NLO and NNLO results with for NLO QED ISR/FSR: studies progressing well Genuine EWK corrections: theory calculations, no MC generator ?!

D.BourilkovDrell-Yan Activities for the EWK Group11 Signal Definition Standard: cross sections calculated in 4; acceptance calculated e.g. by MC Alternative: define signal cross section to cover where we measure e.g. define CMS di-muon cross section with cut on both muons | μ1 |<2.4 and | μ2 |<2.4  Can calculate directly in PYTHIA, HERWIG, FEWZz …  In this approach events with 1 generated muon || > 2.4 are just part of the background  Eliminates the acceptance calculation  Can publish two (sets of) cross sections: in CMS acceptance region and (different) extrapolations to 4 N obs = L..  =  acceptance.  trigger.  offline-reco

D.BourilkovDrell-Yan Activities for the EWK Group12 QCD Corrections – K Functions For a scale 1 * relatively weak mass dependence of the K factors NLO & NNLO NNLO K factors vary by ~ 6 % only from Z to high mass

D.BourilkovDrell-Yan Activities for the EWK Group13 Drell-Yan Event Rates and Normalization Mass [GeV]  TOTAL [pb] Acceptance | 1,2 |<2.4  SEL [pb] Events; Ratio to Z 1 pb -1 [%] Events; Ratio to Z 10 pb -1 [%] Events;Ratio to Z 100pb -1 [%] Rough estimate: no K-functions, no efficiency (ee OR μμ) The statistical errors on a normalization to the Z are shown in the table; the errors from PDF uncertainties are 4-8 % for the 500+ or bins. For 10 pb -1 the DY background to new physics is negligible above 500 GeV, for 100 pb -1 above 1000 GeV, for 1000 pb -1 around 2 TeV. Any statistically significant accumulation of events in these areas would signal new physics.

D.BourilkovDrell-Yan Activities for the EWK Group14 Normalization to Z Peak ‘Data’ Good agreement in ratios between PYTHIA with different PDFs and FEWZz in LO, NLO & NNLO

Drell-Yan Tasks List Task (> need volunteers) e + e - μ + μ - Triggers, datasets and skims : Check that efficiencies are good at low and very-high PT + + Offline reconstruction and resolution a) Use Z mass to calibrate scale b) Obtain resolutions from data c) Port existing code to PAT -- write new code in PAT + + Data driven background estimation methods a) of special importance: machine backgrounds > > QED ISR/FSR studies CommonAdvanced QCD corrections : comparison of MCs CommonAdvanced EWK corrections : investigate if any new MC generators and work with theorists Common > PDF uncertainties CommonAdvanced Fast simulation validation - then use for estimating QCD backgrounds > > Systematic uncertainties W/Z and High mass Notes Analysis of global runs data > >

D.BourilkovDrell-Yan Activities for the EWK Group16 Outlook TWIKI page: task list will appear there – please sign in twiki.cern.ch/twiki/bin/view/CMS/TWikiEWKDrellYan twiki.cern.ch/twiki/bin/view/CMS/TWikiEWKDrellYan Hypernews - interested people can subscribe: Drell-Yan provides tests of the Standard Model at highest momentum transfers (and soon after start-up will push into unexplored territory) Irreducible background for high mass searches Plenty to do before first collisions – feedback and volunteers most welcome CSA07 samples available Test and verify fast simulation for high energy electrons/muons by comparing to full simulation Contacted groups active in high mass (and Z analyses); received feedback from W/Z, HEEP, TeVmu, LPC di-lepton groups

D.BourilkovDrell-Yan Activities for the EWK Group17 Backup Slides

D.BourilkovDrell-Yan Activities for the EWK Group18 PDF Uncertainties PYTHIA CTEQ6.1 Mass [GeV] xsec [pb] PDF Uncertainty [%/100] CTEQ6.1 Cross Section Xsec ratio to Z Xsec ratio toZ Uncorrelated Correlated E E E E E E E E E E E E E E E E

D.BourilkovDrell-Yan Activities for the EWK Group19 PDF Uncertainties PYTHIA MRST2006nnlo Mass [GeV] xsec [pb] PDF Uncertainty [%/100] MRST2006nnlo Cross Section Xsec ratio to Z Xsec ratio toZ Uncorrelated Correlated E E E E E E E E E E E E E E E E