# Presentation: 799077

## d/dy Distribution of Drell-Yan Dielectron Pairs at CDF in Run II

**Jiyeon Han**
**(University of Rochester)**
**For the CDF Collaboration**
**EPS**
**July, 19, 2007**
**Manchester,  England**

- Jiyeon Han (University of Rochester)

- 7/20/07

## Outline

- CDF Run II detector
- Introduction
- Event selection
- Acceptance and efficiencies
- Background
- Systematic uncertainties
- Run II result
- Summary

- Jiyeon Han (University of Rochester)

- 7/20/07

## CDF Run II Detector

** ****Three dielectron topologies :**
**     ****central-central (Z****CC****)**
**     ****central-plug(Z****CP****)**
**     ****plug-plug(Z****PP****)**

** ****Plug calorimeter covers high **** region(1.1< |****| < 3.6)**
** ****Silicon tracking coverage out to |********| < 2.8**
** ****Requiring silicon track matches in forward region reduces background contamination**** **

- Jiyeon Han (University of Rochester)

- 7/20/07

## Introduction

-  Parton momentum fractions (x1,2) determine Z boson rapidity (yZ)
-  Production measurement in high yZ region probes high x region of PDFs
-  Plug-plug (ZPP) event needed to probe highest x region

- Jiyeon Han (University of Rochester)

- 7/20/07

## Data set

- 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 %

-  Total trigger efficiency
-        Zcc : 1.0
-       Zcp : 0.9940.001
-       Zpp : 0.9950.001

- Jiyeon Han (University of Rochester)

- 7/20/07

## Z selection with two central electrons : Zcc
Kinematic selection : ET  25 GeV ,  ||1.1
Two good central electrons
Oppositely charged electrons

Z selection with a central and plug electron : Zcp
Kinematic selection : ET 20 GeV 
                                      ||1.1 for central, 1.2  ||2.8 for plug
One good central electron and plug electron

Z selection with two plug electrons : Zpp
Kinematic selection : ET  25 GeV , 1.2  ||  2.8
Two good plug electrons
Same side events
One electron candidate must have a matched silicon track (~87%)

- Kinematic selection : ET  25 GeV ,  ||1.1
- Two good central electrons
- Oppositely charged electrons
- Z selection with a central and plug electron : Zcp
- Kinematic selection : ET 20 GeV
-                                       ||1.1 for central, 1.2  ||2.8 for plug
- One good central electron and plug electron
- Z selection with two plug electrons : Zpp
- Kinematic selection : ET  25 GeV , 1.2  ||  2.8
- Two good plug electrons
- Same side events
- One electron candidate must have a matched silicon track (~87%)

**Selection**

- Jiyeon Han (University of Rochester)

- 7/20/07

## Mass and Rapidity

**Mass and Rapidity**

- Mass window : 66 < M < 116 GeV/c2

|  | Z(CC) | Z(CP) | Z(PP) |
| --- | --- | --- | --- |
| Events | 28097 | 46676 | 16589 |

***Probes high y region ( ~ 2.9 )***

- Total : 91362 events

- Jiyeon Han (University of Rochester)

- 7/20/07

## Measured Acceptance  Efficiencies in Boson rapidity

Total Acceptance  Efficiencies is 33.5%.
 A  E is flat up to |yZ| ~ 2.0 and non-zero up to |yZ| ~ 2.9 by adding ZPP region

- Total Acceptance  Efficiencies is 33.5%.
-  A  E is flat up to |yZ| ~ 2.0 and non-zero up to |yZ| ~ 2.9 by adding ZPP region

**Acceptance and Efficiencies**

-  MC tuned to data
-     Energy resolution and scale
-     Efficiencies

-  Geometric and kinematic acceptances
-     modeled using Pythia MC and GEANT
-     detector simulation

- Jiyeon Han (University of Rochester)

- 7/20/07

## Backgrounds for Z/* 

- Background estimation (QCD+EWK)
- QCD Background is 0.920.06%
- EWK background is 0.110.01% (WW,WZ, ttbar inclusive,W+jet)

- Jiyeon Han (University of Rochester)

- 7/20/07

## Systematic study

- Systematic uncertainties determined for
- Detector material modeling
- Background estimates
- Electron identification efficiencies
- Silicon tracking efficiency
- Acceptance

-  Largest systematic uncertainties
-     associated with measurement of
-     electron ID efficiency

- Jiyeon Han (University of Rochester)

- 7/20/07

## d/dy distribution I

**d********/dy distribution I**

- d/dy distribution of Z/* (positive and negative rapidity region)

-   (y>0)      : 264.31.4(stat.) pb
-     (y<0)      : 262.51.3(stat.) pb
-   No PDF or luminosity uncertainties included
-    of positive and negative rapidity is consistent

- Jiyeon Han (University of Rochester)

- 7/20/07

## d/dy distribution II

- d/dy distribution of Z/*

-  NLO calculation with NLL CTEQ PDF
-   (Zee) : *263.3± 0.9(stat.)****3.8(sys.)** **pb*
* *No PDF or luminosity uncertainties included

- Jiyeon Han (University of Rochester)

- 7/20/07

**Theory prediction scaled to measured ******** (Z)**
**Only statistic uncertainty considered**** **

**                                                                                                         **

**d********/dy distribution (data/theory)**** **

-  NLO calculation with NLL MRST PDF

-  NLO calculation with NLL CTEQ PDF

- CTEQ PDF describes data better

- Jiyeon Han (University of Rochester)

- 7/20/07

**Theory prediction scaled to measured ******** (Z)**
**Only statistic uncertainty considered**** **

**                                                                                                         **

**d********/dy distribution (data/theory)**** **

-  NLO calculation with NLL MRST PDF

-  NNLO calculation with NNLL MRST PDF

- NNLO calculation is slightly better, but not much different
- Reference for NNLO calculation : Phys.Rev.D69:094008

- Jiyeon Han (University of Rochester)

- 7/20/07

## Summary

- We measure d/dy distribution of Z/*e+e-  up to  |yZ| ~ 2.9
- Total cross section  263.3  0.9(*stat.*)  3.8(*sys.*) *pb*
*No PDF or luminosity uncertainties included*
- Measured d/dy shape :
- Can distinguish between PDFs : CTEQ PDFs has better agreement
- NNLO vs. NLO : NNLO gives marginally better agreement

- Jiyeon Han (University of Rochester)

- 7/20/07

## Backup slide

- Jiyeon Han (University of Rochester)

- 7/20/07

## RunI result 

- PDF predictios

-   LO  CTEQ4 PDF
-   NLO  CTEQ4 PDF
-   d quark enhanced modified
-       NLO CTEQ4 PDF
-   NLO gluon resummated
-       calculation with CTEQ4 PDF

-   not enough to make a distinction better PDF

- Jiyeon Han (University of Rochester)

- 7/20/07

## Boson Rapidity

-  What is the relation between x1,2 and the rapidity in Z boson?

- x**1 ****: Parton momentum fraction from proton**
**x****2 ****: Parton momentum fraction from anti-proton**
**x****1,2**** determine rapidity of Z boson**
**What is the rapidity**** ?**

- Feynman Diagram of Drell-Yan proccess

**P****γ*****/****Z **** = (****x****1****E****B****+**** ****x****2****E****B****, 0, 0,****  ****x****1****E****B****-**** ****x****2****E****B****)**

- ( P: momentum in longitudinal direction )

- Jiyeon Han (University of Rochester)

- 7/20/07

## Et distribution

- Et distribution (data, MC)

- Jiyeon Han (University of Rochester)

- 7/20/07

## Theory Prediction

- Total cross section
- NNLO calculation with NNLL MRST PDF : 251.34pb
- NLO calculation with NLL MRST PDF : 241.01pb
- NLO calculation with NLL CTEQ PDF : 236.14pb

- Jiyeon Han (University of Rochester)

- 7/20/07

## Backgrounds for Z/* : QCD

- Largest background : QCD dijets
- Magnitude obtained from fit to electron isolation distribution
- Isolation defined as energy contained in a R=0.4 cone around an electron minus the energy of the electron itself
- Fit isolation distribution for both signal and background contributions
- Extrapolate the background from high Isolation tail into the signal region
- Total QCD background = 0.920.06%

- Jiyeon Han (University of Rochester)

- 7/20/07

## Systematic Uncertainties

- Systematic uncertainties component

| Systematic Component | / (%) |
| --- | --- |
| Material Effect | 0.13 |
| Background Estimation | 0.44 |
| Tracking Efficiency | 0.15 |
| ID Efficiency | 1.30 |
| Acceptance | 0.13 |

- Jiyeon Han (University of Rochester)

- 7/20/07