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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. - PowerPoint PPT Presentation
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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 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 Q2
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
Asymmetry in W production complicated by unknown pz
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.
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 2/dof
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
We performed various validity and systematic checks
and found it to be robust with small systematics.
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 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<mee<100 and compare central Qtag
Charge ID Measurement
Errors calculated with Bayesian prescription, CDF5894.
fQCOT fQ
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
Data
MC
CDFII Preliminary ∫Ldt=170/pb
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.
BackgroundWe 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 BackgroundQ
CD
fra
ctio
n
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
Overlay CTEQ3,4,5L, GRV98LO, MRST+d/uCTEQ3,4 to 5 have less d/u from Run1 asym. We keep pulling in Run2.
CDFII Preliminary ∫Ldt=170/pb
Compare PDFs to data
CP checkCDFII 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 < ET < 35
35 < ET < 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 GeVCDFII Preliminary ∫Ldt=170/pb
A(||) with 35 < ET < 45 GeVCDFII Preliminary ∫Ldt=170/pb
Conclusion
W asymmetry provides new PDF constraints.