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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  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

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  1. 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

  2. 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.

  3. 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.

  4. Damn the n’s, forward e ahead  Forward electrons with charge id are the key.

  5. 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

  6. Phoenix Tracking

  7. Plug Alignment (CDF6108) Align plug (actually PES) with COT tracks: allow offsets in x,y,z and a rotation in phi

  8. Plug Alignment Measure and correct, iteratively from largest to smallest f, x & y, Z

  9. Internal Alignment Residual misalignments attributed to internal octant offsets Fit for f and radial shifts in each octant.

  10. Consistent internals between bpel08 and bpel09

  11. Residuals look good after alignment We performed various validity and systematic checks and found it to be robust with small systematics.

  12. 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-

  13. 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

  14. Charge ID Measurement CDFII Preliminary ∫Ldt=170/pb fQCOT fQPhx h Errors calculated with Bayesian prescription, CDF5894.

  15. 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

  16. Check kinematic distributions CDFII Preliminary ∫Ldt=170/pb Data MC

  17. Check kinematic distributions CDFII Preliminary ∫Ldt=170/pb Data MC

  18. Holy Phi Data MC

  19. Raw Asymmetry CDFII Preliminary ∫Ldt=170/pb Curve is just a fit to guide the eye.

  20. Raw Asymmetry CDFII Preliminary ∫Ldt=170/pb Curve is just a fit to guide the eye.

  21. 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.

  22. 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.

  23. QCD Background CDFII Preliminary ∫Ldt=170/pb QCD fraction h We use 0.5 ± 0.25. Becomes significant for h >1.8

  24. Corrected Asymmetry CDFII Preliminary ∫Ldt=170/pb

  25. Compare to COT when it is available CDFII Preliminary ∫Ldt=170/pb

  26. Compare PDFs to data CDFII Preliminary ∫Ldt=170/pb CTEQ5L

  27. 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.

  28. CP check CDFII Preliminary ∫Ldt=170/pb

  29. A(|h|) CDFII Preliminary ∫Ldt=170/pb

  30. A(|h|) CDFII Preliminary ∫Ldt=170/pb FMU Compared to Run1 e+m

  31. Getting more sensitivity to AW

  32. Getting more sensitivity to AW 35 < ET < 45 25 < ET < 35

  33. A(h) with 25 < ET < 35 GeV CDFII Preliminary ∫Ldt=170/pb

  34. A(|h|) with 25 < ET < 35 GeV CDFII Preliminary ∫Ldt=170/pb

  35. A(h) with 35 < ET < 45 GeV CDFII Preliminary ∫Ldt=170/pb

  36. A(|h|) with 35 < ET < 45 GeV CDFII Preliminary ∫Ldt=170/pb

  37. Conclusion W asymmetry provides new PDF constraints.

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