Drell-Yan Activities for the EWK Group Dimitri Bourilkov University of Florida LPC Di-lepton...

Drell-Yan Activities for the EWK Group

Dimitri BourilkovDimitri BourilkovUniversity of FloridaUniversity of Florida

LPC Di-lepton Meeting, FNAL, March 27,LPC Di-lepton Meeting, FNAL, March 27, 2008 2008

D.BourilkovD.Bourilkov Drell-Yan Activities for the EWK Group 2

Introduction

• LHC is a high mass di-lepton factory

• Already with ~100 pb-1 we will be probing regions @ 800+ GeV

• Be ready to move to high masses immediately after demonstrating the Z peak performance


Drell-Yan Task

• Scope: study ee, μμ, eμ above (at startup – also below) 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 TeVmu groups

For 1-100 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 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 resolutions

for ee and μμ have opposite pT dependence, this will provide an important handle

> AFB @ Z, below Z and @ 100-200 GeV should be ~equal


Efficiencies & Resolutions

• Efficiencies from data: tag and probeAt 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: advancedMomentum scale calibrationHigh mass: limited statistics, no peak; pT balancing

for μ+μ- ?!; leapfrog method for e+e- – how far can we go for lumi < 1fb-1?


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)

BtoJpsiQCD_Pt_0_15CharmoniumBottomoniumElectron_ppEleXMuon_ppMuX

• Gumbo: (/CSA07Muon/CMSSW_1_6_7-CSA07-Tier0-A1-Gumbo/RECO)

"Hard" QCD dijets (pT_hat >15 GeV)Minimum biasGamma+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 weights

for 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. 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 χ2/dof (no quality cuts applied yet).

Dimuon mass spectra w/o isolation cut

Opposite sign

Same sign

Without isolation cut (and pT > 20 GeV cut):

M. Chen (Beijing), Univ. of Florida

• Require ΣpT (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


Efficiency as a function of a ΣpT (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 pT > 20 GeV cut):


Opposite sign

PAS

PAS


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: theory calculations, no MC generator ?!


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

Nobs = L.. = acceptance . trigger . offline-reco


QCD Corrections – K Functions

• For a scale 1 * <M> relatively weak mass dependence of the K factors both @ NLO & NNLO

• NNLO K factors vary by ~ 6 % only from Z to high mass


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 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.


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 Common Advanced

QCD corrections: comparison of MCs Common Advanced

EWK corrections: investigate if any new MC generators and work with theorists

Common >

PDF uncertainties Common Advanced

Fast simulation validation - then use for estimating QCD backgrounds

> >

Systematic uncertainties W/Z andHigh mass Notes

Analysis of global runs data > >


Outlook• TWIKI page: task list will appear there – please sign in

https://twiki.cern.ch/twiki/bin/view/CMS/TWikiEWKDrellYan

• Hypernews - interested people can subscribe: [email protected]

• 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




Backup Slides


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


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

Drell-Yan Activities for the EWK Group Dimitri Bourilkov University of Florida LPC Di-lepton...

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