# Presentation: 199644

## W Charge asymmetry

***Cigdem Issever, Adam Scott, and David Stuart***
***UCSB***

***Preblessing, EWK 5/13/04***

***CDF Note 6282, ***Measurement of W e Charge Asymmetry
***CDF Note 6108, ***Alignment of the Plug Calorimeter
***CDF Note 6412, ***QCD Background for Plug Ws

## Motivation

***W******±****** charge asymmetry arises from u(x)/d(x) in proton.***
***Gives most sensitive u/d constraint at our x and Q******2***
***But still not well constrained at high x (high ************.***
*** ******We don’t already know the answer.***
***     ******Experimentally appealing.***
***Can improve many of our forthcoming measurements.***

## Damn the ’s. forward e ahead

**Damn the ********’s.**** forward e ahead**

***Asymmetry in W production complicated by unknown ************ p******z***

***So, use lepton asymmetry***

***Which convolves production asymmetry with V-A decay.***

## Damn the ’s, forward e ahead

*** ************ ******Forward electrons with charge id are the key. ***

## Phoenix Tracking

- define a unique helix:
-  Primary vertex
-  Shower Max cluster
-  ET  |C|

- Attach hits using OI tracking

- Select track with better 2/dof

**Phoenix Tracking**

## Phoenix Tracking

**Phoenix Tracking**

## Plug Alignment (CDF6108)

***Align plug (actually PES) with COT tracks:***
***  ******allow offsets in x,y,z and a rotation in phi ***

## Plug Alignment

***Measure and correct, iteratively from largest to smallest***
*********, x & y, Z ***

## Internal Alignment

***Residual misalignments attributed to internal octant offsets***

***Fit for ************and radial shifts in each octant.***

## Consistent internals between bpel08 and bpel09

## Residuals look good after alignment

**Residuals look good after alignment**

- We performed various validity and systematic checks
- and found it to be robust with small systematics.

## Measured fQ() with Z e+e- 

- Incorrectly identifying the charge dilutes the asymmetry.
- We can correct for it if we know the rate, fQ # wrong / total

- Atrue = Ameas / (1-2fQ)

- So make fQ small and measure it.
- MC predicts fQ ≈ 1%.
- But MC doesn’t know about residual mis-alignments etc.
- We must measure it in data and cannot assume any  dependence.
- Measured fQ() with Z e+e-

## Z Event Selection

- Baseline electron selection with COT or PHX track. ET>25 GeV
- PHX track is slightly non-standard to optimize fQ.
-     # hits >= 4
-     2 < 8
-     2 > 0.5
-     Seed Pull < 0.4

***80<m******ee******<100  and compare central Qtag***

## Charge ID Measurement

- Errors calculated with Bayesian prescription, CDF5894.

******

***f******Q******COT***

***f******Q******Phx***

- CDFII Preliminary ∫Ldt=170/pb

## W Event Selection

- Baseline electron selection w/ PHX track.
-    ET>25 GeV
-    Missing ET > 25 GeV
-    50 < MT < 100 GeV/c2
- No other EMO with ET>25 GeV
-    to suppress QCD and DY

## Check kinematic distributions

***Data***
***MC***

- CDFII Preliminary ∫Ldt=170/pb

## Check kinematic distributions

**Check kinematic distributions**

***Data***
***MC***

- CDFII Preliminary ∫Ldt=170/pb

## Holy Phi

**Holy Phi**

***Data***
***MC***

## Raw Asymmetry

- CDFII Preliminary ∫Ldt=170/pb

- Curve is just a fit to guide the eye.

## Raw Asymmetry

- CDFII Preliminary ∫Ldt=170/pb

- Curve is just a fit to guide the eye.

##  Z e+e- 

**Background**

- We correct the asymmetry for backgrounds from:
-  W   e
-       Asymmetric, measured from MC
-  Z e+e-
-       Asymmetric, measured from MC
-  QCD
-       Symmetric, measured from data  CDF 6412.
-              Use Iso vs MET.

## QCD Background systematic

- Check assumption of non-correlation
- small systematic, as long as we don’t use the
-     PEM 3x3 2 or 5x9 cuts (they are correlated with Iso)
-       upper limit by about a factor of 2.

## QCD Background

***QCD fraction***

******

- We use 0.5 ± 0.25.  Becomes significant for >1.8

- CDFII Preliminary ∫Ldt=170/pb

## Corrected Asymmetry

- CDFII Preliminary ∫Ldt=170/pb

## Compare to COT when it is available

- CDFII Preliminary ∫Ldt=170/pb

## Compare PDFs to data

- CDFII Preliminary ∫Ldt=170/pb

- CTEQ5L

## Compare PDFs to data

- CTEQ3,4 to 5 have less d/u from Run1 asym. We keep pulling in Run2.

- CDFII Preliminary ∫Ldt=170/pb

**Compare PDFs to data**

## CP check

- CDFII Preliminary ∫Ldt=170/pb

## A(||)

- CDFII Preliminary ∫Ldt=170/pb

## A(||)

***Compared to ******Run1 e+*********

***FMU***

- CDFII Preliminary ∫Ldt=170/pb

## Getting more sensitivity to AW

## Getting more sensitivity to AW

***25 < E******T****** < 35***

***35 < E******T****** < 45***

## A() with 25 < ET < 35 GeV

- CDFII Preliminary ∫Ldt=170/pb

## A(||) with 25 < ET < 35 GeV

- CDFII Preliminary ∫Ldt=170/pb

## A() with 35 < ET < 45 GeV

- CDFII Preliminary ∫Ldt=170/pb

## A(||) with 35 < ET < 45 GeV

- CDFII Preliminary ∫Ldt=170/pb

## Conclusion

***W asymmetry provides new PDF constraints. ***