d&sigma/dy Distribution of Drell-Yan Dielectron Pairs with 1.1 /fb

Authors: Jiyeon Han, Arie Bodek, Willis Sakumoto, Y.S.Chung
Last Updated: Jul, 15th, 2007

Public Note

Abstract

We report on the measurement of the rapidity distribution, d&sigma/dy, over the full kinematic range for e+e- pairs in the Z boson region of the mass range, 66 to 116 GeV/c^2. The data sample is consistent of 1.1/fb of ppbar collisions at (s)½ = 1.96 TeV taken by the Collider Detector at Fermilab. d&sigma/dy are compared with theory prediction.

Data set and Trigger Efficiency

data sample : ~ 1.1 fb-1
Inclusive single central electron trigger
Two electron trigger (central or forward)
Trigger efficiency measured as a function of electron Et
Overall trigger efficiency ~ 100%

Z(CC) Z(CP) Z(PP)
1.0 0.9936+-0.0001 0.9953+-0.0001

Event Selection

Two high pt electron for reconstructing Z events.
(Et>25GeV for Zcc and Zcp, Et>20GeV for Zcp)
Electron identification requirement applied
Same charge events required for Zcc events.
Same side dielectron required for Zpp events.
One silicon track required for Zpp events.

After Z selection, we get 91362 Z boson events.


Z(CC) Z(CP) Z(PP)
Events 28097+-168 46676+-216 16589+-129
Mass 90.75+-0.03 90.45+-0.02 90.03+-0.04
Width 2.95+-0.03 3.13+-0.03 3.19+-0.05

Acceptance and Efficiency

After kinematic requirement, 44.37% events accepted

Z(CC) Z(CP) Z(PP)
Acceptance 0.1128+-0.0002 0.2363+-0.0002 0.0946+-0.0001
Efficiency 0.904+-0.003 0.718+-0.008 0.774+-0.021

Background

Consider QCD and EWK background

QCD background
Z(CC) Z(CP) Z(PP) Total
0.38+-0.08%(stat.) 0.65+-0.08% 2.62+-0.22% 0.92+-0.06%

EWK background is 0.11+-0.01% in total.
Total background rate is 1.03+-0.06%(stat.)
For systematic uncertainty for QCD background, we assign 30% systematic uncertianty.

Result

&sigma = 263.34± 0.93(stat.)± 3.79(sys.) pb.
&sigma(y>0) = 264.32± 1.38(stat.)± 3.93(sys.) pb.
&sigma(y<0) = 262.48± 1.28(stat.)± 3.73(sys.) pb.
No PDF or luminosity uncertainties included.
Theory predictions scaled to measured &sigma (Z).
NLO calculation with NLO CTEQ6.1 PDF describes data best

Plots

The relation of the parton momentum fraction and rapidity of Z boson
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Dielectron invariant mass distribution of each region
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Z rapidity distribution
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Trigger efficiency as a function of Z boson rapidity.
Blue: Zcc, Magenta: Zcp, Red: Zpp
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Acceptance x Z efficiency distribution as a function of Z boson rapidity.
MC tuned to data by energy resolution and scale and electron ID efficiency.
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Acceptance x efficiencies distribution as a function of Z boson rapidity.
MC tuned to data by energy resolution and scale, electron ID efficiency, and silicon tracking.
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Track efficiency
The scale factor of the silicon tracking efficiency in terms of expected silicon layers
The expected silicon layers is calculated by ZVertex and calorimeter position
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Track efficiency
The selection efficiency of requiring at least one silicon track as a function of the Z boson rapidity in Zpp
It's determined from corrected MC
Total efficiency is 0.8670+-0.0005
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Data and background distribution
Brown: EWK background, Green: QCD background
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Data and background distribution
Brown: EWK background, Green: QCD background
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Systematic uncertainty as a function of Z boson rapidity.
Systematic uncertainties determined for
- Detector material modelling
- Background estimates
- Electron identification efficiencies
- Silicon tracking efficiency
- Acceptance
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d&sigma/dy distribution of positive and negative rapidity.
No PDF or luminosity uncertainty included.
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d&sigma/dy distribution of Z/&gamma* -> e+e-.
No PDF or luminosity uncertainty included in data.
NLO calculation with NLO CTEQ6.1 PDF theory prediction compared to data.
Theory prediction scaled to total cross section from data.
Residual.
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d&sigma/dy distribution of Z/&gamma* -> e+e-.
No PDF or luminosity uncertainty included in data.
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Fraction of data and theory prediction I.
NNLO calculation with NNLL MRST PDF theory prediction used.
Theory prediction scaled to total cross section from data.
statistic uncertainty only.
chi2 = 56.886/30
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Fraction of data and theory prediction II.
NLO calculation with NLL CTEQ6.1 PDF theory prediction used.
Theory prediction scaled to total cross section from data.
statistic uncertainty only.
chi2 = 29.916/30
.gif
Fraction of data and theory prediction III.
NLO calculation with NLL MRST PDF theory prediction used.
Theory prediction scaled to total cross section from data.
statistic uncertainty only.
chi2 = 66.552/30
.gif
Fraction of data and theory prediction I.
NNLO calculation with NNLL MRST PDF theory prediction used.
Theory prediction scaled to total cross section from data.
.gif
Fraction of data and theory prediction II.
NLO calculation with NLO CTEQ6.1 PDF theory prediction used.
Theory prediction scaled to total cross section from data.
.gif
Fraction of data and theory prediction III.
NLO calculation with NLO MRST PDF theory prediction used.
Theory prediction scaled to total cross section from data.
.gif

 

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