Drell-Yan Activitiesfor the EWK Group
Dimitri BourilkovDimitri Bourilkov
University of FloridaUniversity of Florida
LPC Di-lepton Meeting, FNAL, March 27, 2008LPC Di-lepton Meeting, FNAL, March 27, 2008
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Introduction
•LHC is a high massdi-lepton factory
•Already with ~100pb-1 we will beprobing regions @800+ GeV
•Be ready to move tohigh massesimmediately afterdemonstrating the Zpeak performance
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Drell-Yan Task
•Scope: study ee, μμ, eμ above (at startup – alsobelow) the Z peak; ?
•Measure cross sections and (later) AFB
•Existing work:
Use results from W/Z ee and μμ groups as a baseline;augment with high mass studies from HEEP and TeVmugroups
For 1-100 pb-1 extrapolation to higher masses will requireMC and (to limited extent due to low event rates) datadriven methods. Use ratios where possible. The residualdependence on pT and mass will need simulation inputs
Combining ee and μμ (and eμ) results - vital crosschecks:
>cross sections should be ~ equal
>same for DY mass spectra (slope), ratios to Z, etc.; as the resolutionsfor ee and μμ have opposite pT dependence, this will provide animportant handle
>AFB @ Z, below Z and @ 100-200 GeV should be ~equal
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Efficiencies & Resolutions
•Efficiencies from data: tag and probe
At Z:
>trigger efficiencies
>offline efficiencies
Higher mass:
>can not go higher than <~ 250-300 GeV for 100 pb-1 due to limited statistics
>backgrounds can be difficult
•Resolutions from data (pT, mass):
Fit Z mass spectrum: advanced
Momentum scale calibration
High mass: limited statistics, no peak; pT balancingfor μ+μ- ?!; leapfrog method for e+e- – how far canwe go for lumi < 1fb-1?
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Backgrounds
•MC studies progressing well (CSA07soups)
•Data driven methods for jet-jetbackgrounds (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 masscut.
•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 (pT_hat >15 GeV)
Minimum bias
Gamma+jets
•WW, WZ, ZZ:
/WW_incl/CMSSW_1_6_7-CSA07-1198096665/AODSIM
/WZ_incl/CMSSW_1_6_7-CSA07-1198096684/AODSIM
/ZZ_incl/CMSSW_1_6_7-CSA07-1198096655/AODSIM
•Compare results with the Drell-Yan background and Z′ signal.
Use CSA07 background samples
(https://twiki.cern.ch/twiki/bin/view/CMS/DigiRecoCSA07Signal)
Studies of non-Drell-Yan backgrounds
1.Run over all events in these datasets.
2.Use CSA07EventWeightProducer (v06-15-08-03) to get weightsfor 100 pb−1.
3.Require OR of non-isolated single-muon and dimuon triggers.
4.Require two muons with Mμμ > 400 GeV.
Mingshui Chen(Beijing), Univ. ofFlorida
•Dijet contribution is ~ as big as Drell-Yan in opp.-sign sample, anddominates same-sign.
•Two large-weight events from μX: b-bbar with p=30 TeV, and c-cbar withvery poor χ2/dof (no quality cutsapplied yet).
Dimuon mass spectra w/o isolation cut
Opposite sign
Same sign
Without isolation cut (and pT > 20 GeV cut):
M. Chen(Beijing),Univ. ofFlorida
•Require ΣpT (in a cone ofΔR=0.3) < 10 GeV.
QCD background issuppressed by anorder of magnitude.
Signal (and Drell-Yan)efficiency go down by1-2%.
•Events rejected by thecut (as well as same-signevents before the cut)can be used to study QCDbackground.
Isolation cut
M. Chen (Beijing),Univ. of Florida
Efficiency as a function of a ΣpT (ina 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-bbarand c-cbar.
Dimuon mass spectra w/ isolation cut
Same sign
Apply isolation cut (and pT > 20 GeV cut):
M. Chen(Beijing),Univ. ofFlorida
Opposite sign
PAS
PAS
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Theory / Monte Carlo
•Many things in common for ee and μμ
•PDF uncertainties: well advanced
•QCD corrections:
results with FEWZz @ NLO and NNLO
results with MC@NLO for NLO
•QED ISR/FSR: studies progressing well
•Genuine EWK corrections: theorycalculations, no MC generator ?!
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Signal Definition
•Standard: cross sections calculated in 4;acceptance calculated e.g. by MC
•Alternative: define signal cross section to coverwhere we measure e.g. define CMS di-muon crosssection 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 CMSacceptance region and (different) extrapolations to4
Nobs = L.. = acceptance . trigger . offline-reco
D.Bourilkov
Drell-Yan Activities for the EWK Group
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QCD Corrections – K Functions
•For a scale 1 * <M> relatively weak massdependence of the K factors both @ NLO & NNLO
•NNLO K factors vary by ~ 6 % only from Z to highmass
D.Bourilkov
Drell-Yan Activities for the EWK Group
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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 [%]
70-120
1620
0.430
697
700 -
7000 -
70000 -
120+
18.8
0.483
9.1
9 33
90 10.5
900 3.3
250+
1.2
0.595
0.70
0.7 120
7 37.8
70 12.0
500+
0.099
0.724
0.072
-
0.7 120
7 37.8
1000+
0.0065
0.846
0.0055
-
-
0. 6 129
2000+
0.00024
0.920
0.00022
-
-
-
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 1000+bins. For 10 pb-1 the DY background to new physics is negligibleabove 500 GeV, for 100 pb-1 above 1000 GeV, for 1000 pb-1 around 2TeV. Any statistically significant accumulation of events in theseareas would signal new physics.
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Normalization to Z Peak ‘Data’
Good agreement in ratios between PYTHIA withdifferent PDFs and FEWZz in LO, NLO & NNLO
Drell-Yan Tasks List
Task (> need volunteers)
e+e-
μ+μ-
Triggers, datasets and skims: Check thatefficiencies 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
Common
Advanced
QCD corrections: comparison of MCs
Common
Advanced
EWK corrections: investigate if any new MCgenerators and work with theorists
Common
>
PDF uncertainties
Common
Advanced
Fast simulation validation - then use forestimating QCD backgrounds
>
>
Systematic uncertainties
W/Z and
High mass Notes
Analysis of global runs data
>
>
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Outlook
•TWIKI page: task list will appear there – please sign inhttps://twiki.cern.ch/twiki/bin/view/CMS/TWikiEWKDrellYan
•Hypernews - interested people can subscribe:hn-cms-ewk-drellyan@cern.ch
•Drell-Yan provides tests of the Standard Model at highestmomentum transfers (and soon after start-up will pushinto unexplored territory)
•Irreducible background for high mass searches
•Plenty to do before first collisions – feedback andvolunteers most welcome
•CSA07 samples available
•Test and verify fast simulation for high energyelectrons/muons by comparing to full simulation
•Contacted groups active in high mass (and Z analyses);received feedback from W/Z, HEEP, TeVmu, LPC di-leptongroups
D.Bourilkov
Drell-Yan Activities for the EWK Group
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Backup Slides
D.Bourilkov
Drell-Yan Activities for the EWK Group
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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
• 0040-0060 41.07933 + 0.067 - 0.079 + 0 - 0 + 0 - 0
• 0060-0080 29.11724 + 0.058 - 0.075 + 0 - 0 + 0 - 0
• 0080-0100 650.3979 + 0.053 - 0.073 + 0 - 0 + 0 - 0
• 0100-0120 20.91373 + 0.050 - 0.071 + 0.074 - 0.102 + 0.004 - 0.005
• 0120-0140 4.166503 + 0.047 - 0.067 + 0.071 - 0.100 + 0.010 - 0.010
• 0140-0160 1.773516 + 0.045 - 0.066 + 0.070 - 0.098 + 0.014 - 0.015
• 0160-0180 0.9442186 + 0.043 - 0.063 + 0.069 - 0.097 + 0.019 - 0.019
• 0180-0200 0.5534378 + 0.041 - 0.061 + 0.068 - 0.096 + 0.022 - 0.023
• 0200-0300 1.047500 + 0.040 - 0.058 + 0.067 - 0.093 + 0.030 - 0.030
• 0300-0400 0.2334509 + 0.038 - 0.053 + 0.066 - 0.090 + 0.042 - 0.040
• 0400-0500 0.7916863E-01 + 0.038 - 0.050 + 0.066 - 0.088 + 0.051 - 0.047
• 0500-0600 0.3307076E-01 + 0.039 - 0.049 + 0.066 - 0.088 + 0.058 - 0.053
• 0600-0700 0.1550730E-01 + 0.040 - 0.050 + 0.067 - 0.089 + 0.064 - 0.057
• 0700-0800 0.7982878E-02 + 0.042 - 0.051 + 0.068 - 0.089 + 0.071 - 0.062
• 0800-0900 0.4451912E-02 + 0.043 - 0.052 + 0.069 - 0.090 + 0.075 - 0.066
• 0900-1000 0.2634348E-02 + 0.045 - 0.054 + 0.070 - 0.091 + 0.080 - 0.069
• 1000-1500 0.4326681E-02 + 0.049 - 0.058 + 0.072 - 0.094 + 0.090 - 0.076
• 1500-2000 0.6327142E-03 + 0.061 - 0.068 + 0.081 - 0.100 + 0.109 - 0.088
• 2000-2500 0.1307343E-03 + 0.077 - 0.079 + 0.094 - 0.108 + 0.131 - 0.100
• 2500-3000 0.3304343E-04 + 0.101 - 0.093 + 0.114 - 0.118 + 0.158 - 0.114
• 3000-3500 0.9280736E-05 + 0.128 - 0.110 + 0.139 - 0.132 + 0.186 - 0.133
• 3500-4000 0.2832010E-05 + 0.166 - 0.133 + 0.175 - 0.152 + 0.225 - 0.158
• 4000-4500 0.9166083E-06 + 0.208 - 0.160 + 0.215 - 0.176 + 0.267 - 0.185
• 4500-5000 0.3097030E-06 + 0.267 - 0.189 + 0.272 - 0.203 + 0.330 - 0.214
• 5000-5500 0.1052451E-06 + 0.340 - 0.220 + 0.344 - 0.232 + 0.407 - 0.246
• 5500-6000 0.3560790E-07 + 0.434 - 0.251 + 0.437 - 0.261 + 0.506 - 0.277
D.Bourilkov
Drell-Yan Activities for the EWK Group
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PDF Uncertainties PYTHIA MRST2006nnlo
•Mass [GeV] xsec [pb] PDF Uncertainty [%/100] MRST2006nnlo
• Cross Section Xsec ratio to Z Xsec ratio toZ
• Uncorrelated Correlated
• 0040-0060 43.31540 + 0.022 - 0.024 + 0 - 0 + 0 - 0
• 0060-0080 31.37652 + 0.021 - 0.024 + 0 - 0 + 0 - 0
• 0080-0100 711.2241 + 0.020 - 0.024 + 0 - 0 + 0 - 0
• 0100-0120 22.31959 + 0.018 - 0.023 + 0.027 - 0.034 + 0.001 - 0.002
• 0120-0140 4.445462 + 0.017 - 0.022 + 0.026 - 0.033 + 0.004 - 0.004
• 0140-0160 1.873783 + 0.015 - 0.022 + 0.025 - 0.032 + 0.006 - 0.006
• 0160-0180 0.9922243 + 0.014 - 0.021 + 0.025 - 0.032 + 0.007 - 0.007
• 0180-0200 0.5824341 + 0.013 - 0.020 + 0.024 - 0.031 + 0.008 - 0.009
• 0200-0300 1.089530 + 0.012 - 0.018 + 0.023 - 0.030 + 0.011 - 0.011
• 0300-0400 0.2444447 + 0.010 - 0.016 + 0.022 - 0.029 + 0.015 - 0.015
• 0400-0500 0.8363874E-01 + 0.009 - 0.014 + 0.022 - 0.028 + 0.018 - 0.018
• 0500-0600 0.3411233E-01 + 0.010 - 0.013 + 0.022 - 0.027 + 0.021 - 0.021
• 0600-0700 0.1597897E-01 + 0.010 - 0.013 + 0.022 - 0.027 + 0.023 - 0.023
• 0700-0800 0.8369605E-02 + 0.012 - 0.013 + 0.023 - 0.027 + 0.026 - 0.024
• 0800-0900 0.4557460E-02 + 0.013 - 0.014 + 0.024 - 0.028 + 0.028 - 0.026
• 0900-1000 0.2710390E-02 + 0.015 - 0.015 + 0.025 - 0.028 + 0.031 - 0.028
• 1000-1500 0.4430216E-02 + 0.020 - 0.018 + 0.029 - 0.030 + 0.036 - 0.031
• 1500-2000 0.6344162E-03 + 0.036 - 0.026 + 0.041 - 0.036 + 0.050 - 0.038
• 2000-2500 0.1321555E-03 + 0.059 - 0.039 + 0.062 - 0.046 + 0.070 - 0.047
• 2500-3000 0.3309892E-04 + 0.087 - 0.054 + 0.089 - 0.059 + 0.096 - 0.059
• 3000-3500 0.9441089E-05 + 0.123 - 0.070 + 0.125 - 0.074 + 0.131 - 0.073
• 3500-4000 0.2948886E-05 + 0.166 - 0.087 + 0.167 - 0.091 + 0.172 - 0.089
• 4000-4500 0.9577241E-06 + 0.210 - 0.104 + 0.211 - 0.107 + 0.215 - 0.105
• 4500-5000 0.3230551E-06 + 0.253 - 0.120 + 0.254 - 0.123 + 0.257 - 0.120
• 5000-5500 0.1090954E-06 + 0.294 - 0.138 + 0.294 - 0.140 + 0.298 - 0.137
• 5500-6000 0.3693165E-07 + 0.327 - 0.154 + 0.328 - 0.156 + 0.331 - 0.153