W Charge asymmetry
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W Charge asymmetry. Cigdem Issever, Adam Scott, and David Stuart UCSB. Preblessing, EWK 5/13/04. CDF Note 6282, Measurement of W  e n Charge Asymmetry CDF Note 6108, Alignment of the Plug Calorimeter CDF Note 6412, QCD Background for Plug Ws. Motivation.

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W charge asymmetry

W Charge asymmetry

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

Motivation

  • 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.


W charge asymmetry

Damn the n’s. forward e ahead

Asymmetry in W production complicated by unknown n pz

So, use lepton asymmetry

Which convolves production asymmetry with V-A decay.


W charge asymmetry

Damn the n’s, forward e ahead

 Forward electrons with charge id are the key.


W charge asymmetry

Phoenix Tracking

  • 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


W charge asymmetry

Phoenix Tracking


Plug alignment cdf6108

Plug Alignment (CDF6108)

Align plug (actually PES) with COT tracks:

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


W charge asymmetry

Plug Alignment

Measure and correct, iteratively from largest to smallest

f, x & y, Z


W charge asymmetry

Internal Alignment

Residual misalignments attributed to internal octant offsets

Fit for f and radial shifts in each octant.


W charge asymmetry

Consistent internals between bpel08 and bpel09


W charge asymmetry

Residuals look good after alignment

We performed various validity and systematic checks

and found it to be robust with small systematics.


W charge asymmetry

Charge ID

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-


W charge asymmetry

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

c2 < 8

Dc2 > 0.5

Seed Pull < 0.4

80<mee<100 and compare central Qtag


W charge asymmetry

Charge ID Measurement

CDFII Preliminary ∫Ldt=170/pb

fQCOT

fQPhx

h

Errors calculated with Bayesian prescription, CDF5894.


W charge asymmetry

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


W charge asymmetry

Check kinematic distributions

CDFII Preliminary ∫Ldt=170/pb

Data

MC


W charge asymmetry

Check kinematic distributions

CDFII Preliminary ∫Ldt=170/pb

Data

MC


W charge asymmetry

Holy Phi

Data

MC


W charge asymmetry

Raw Asymmetry

CDFII Preliminary ∫Ldt=170/pb

Curve is just a fit to guide the eye.


W charge asymmetry

Raw Asymmetry

CDFII Preliminary ∫Ldt=170/pb

Curve is just a fit to guide the eye.


W charge asymmetry

Background

  • 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.


W charge asymmetry

QCD Background systematic

  • 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.


W charge asymmetry

QCD Background

CDFII Preliminary ∫Ldt=170/pb

QCD fraction

h

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


W charge asymmetry

Corrected Asymmetry

CDFII Preliminary ∫Ldt=170/pb


W charge asymmetry

Compare to COT when it is available

CDFII Preliminary ∫Ldt=170/pb


W charge asymmetry

Compare PDFs to data

CDFII Preliminary ∫Ldt=170/pb

CTEQ5L


W charge asymmetry

Compare PDFs to data

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.


W charge asymmetry

CP check

CDFII Preliminary ∫Ldt=170/pb


W charge asymmetry

A(|h|)

CDFII Preliminary ∫Ldt=170/pb


W charge asymmetry

A(|h|)

CDFII Preliminary ∫Ldt=170/pb

FMU

Compared to Run1 e+m


W charge asymmetry

Getting more sensitivity to AW


W charge asymmetry

Getting more sensitivity to AW

35 < ET < 45

25 < ET < 35


W charge asymmetry

A(h) with 25 < ET < 35 GeV

CDFII Preliminary ∫Ldt=170/pb


W charge asymmetry

A(|h|) with 25 < ET < 35 GeV

CDFII Preliminary ∫Ldt=170/pb


W charge asymmetry

A(h) with 35 < ET < 45 GeV

CDFII Preliminary ∫Ldt=170/pb


W charge asymmetry

A(|h|) with 35 < ET < 45 GeV

CDFII Preliminary ∫Ldt=170/pb


W charge asymmetry

Conclusion

W asymmetry provides new PDF constraints.


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