Drell-Yan Task: Introduction

Drell-Yan Task: Introduction

Dimitri BourilkovDimitri BourilkovUniversity of FloridaUniversity of Florida

Drell-Yan EWK Meeting 1, CMS, April 28,Drell-Yan EWK Meeting 1, CMS, April 28, 2008 2008

D.BourilkovD.Bourilkov Drell-Yan Task: Introduction 2

Introduction

• LHC is a high mass di-lepton factory

• Already with ~100 pb-1 @ 14 TeV we will be probing regions @ 800+ GeV

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

Cumulative plots


Drell-Yan Task

• Scope: study ee, μμ, eμ above (at startup – also below) the Z peak; ?

• Bridge the gap between Z - high mass• 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 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 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)

• Top-pair background similar for e+e- and μ+μ-

• Electrons: machine background?

• Muons: cosmics: studies underway

machine background:

> beam halo

> neutrons? need more study


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 single MC generator but recent progress with MC@NLO + HORACE and HERWIG parton showering


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


Drell-Yan Event Rates @ 10 TeV

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 [%]

40-70 117.2 0.357 41.9 42 - 420 - 4200 -

70-120 1129 0.478 540 540 - 5400 - 54000 -

120+ 13.2 0.515 6.8 7 38 70 12.0 700 3.8

250+ 0.78 0.628 0.49 0.5 140 5 44.7 50 14.1

500+ 0.058 0.741 0.043 - 0.4 160 4 50

1000+ 0.0029 0.806 0.0024 - - 0. 2 220

2000+ 0.00006 0.823 0.00005 - - -

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 1 TeV. Any statistically significant accumulation of events in these areas would signal new physics.

Evolving 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: work with theorists Common +PDF uncertainties Common Advance

dFast simulation validation - then use for estimating QCD backgrounds

> >

Systematic uncertainties W/Z andHigh mass Notes

Physics @ 10 TeV Starting >

Analysis of global runs data > >


Outlook

• TWIKI page: evolving task list posted there – please sign in and add missed or “forgotten” tasks 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 Z and high mass analyses;

received feedback from W/Z, HEEP, TeVmu, LPC di-lepton groups

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

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


Backup Slides


Normalization to Z Peak ‘Data’ @ 14 TeV

Good agreement in ratios between PYTHIA with different PDFs and FEWZz in LO, NLO & NNLO


PDF Uncertainties PYTHIA CTEQ6.1 @ 14 TeV

• 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 @ 14 TeV

• 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 Task: Introduction

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