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Cigdem Issever, Adam Scott, and David Stuart

UCSB

Preblessing, EWK 5/13/04

- CDF Note 6282, Measurement of W en Charge Asymmetry
- CDF Note 6108, Alignment of the Plug Calorimeter
- CDF Note 6412, QCD Background for Plug Ws

- W± charge asymmetry arises from u(x)/d(x) in proton.
- Gives most sensitive u/d constraint at our x and Q2
- But still not well constrained at high x (high h).
- We don’t already know the answer.

Experimentally appealing.

Can improve many of our forthcoming measurements.

Asymmetry in W production complicated by unknown n pz

So, use lepton asymmetry

Which convolves production asymmetry with V-A decay.

Forward electrons with charge id are the key.

- Two points and a curvature
- define a unique helix:
- Primary vertex
- Shower Max cluster
- ET |C|

Attach hits using OI tracking

Select track with better c2/dof

Plug Alignment (CDF6108)

Align plug (actually PES) with COT tracks:

allow offsets in x,y,z and a rotation in phi

Residual misalignments attributed to internal octant offsets

Fit for f and radial shifts in each octant.

Residuals look good after alignment

We performed various validity and systematic checks

and found it to be robust with small systematics.

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 h dependence.

Measured fQ(h) with Z e+e-

Baseline electron selection with COT or PHX track. ET>25 GeV

PHX track is slightly non-standard to optimize fQ.

# hits >= 4

c2 < 8

Dc2 > 0.5

Seed Pull < 0.4

80<mee<100 and compare central Qtag

CDFII Preliminary ∫Ldt=170/pb

fQCOT

fQPhx

h

Errors calculated with Bayesian prescription, CDF5894.

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

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

- Check assumption of non-correlation
- small systematic, as long as we don’t use the

PEM 3x3 c2 or 5x9 cuts (they are correlated with Iso)

upper limit by about a factor of 2.

CDFII Preliminary ∫Ldt=170/pb

QCD fraction

h

We use 0.5 ± 0.25. Becomes significant for h >1.8

CDFII Preliminary ∫Ldt=170/pb

Compare to COT when it is available

CDFII Preliminary ∫Ldt=170/pb

CDFII Preliminary ∫Ldt=170/pb

Overlay CTEQ3,4,5L, GRV98LO, MRST+d/u

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

CDFII Preliminary ∫Ldt=170/pb

CDFII Preliminary ∫Ldt=170/pb

CDFII Preliminary ∫Ldt=170/pb

CDFII Preliminary ∫Ldt=170/pb

CDFII Preliminary ∫Ldt=170/pb

CDFII Preliminary ∫Ldt=170/pb

W asymmetry provides new PDF constraints.

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