Electroweak Measurements at CDF

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Electroweak Measurements at CDF
A. Sidoti For the CDF Collaboration LPNHE-
Universite Paris VI Pierre et Marie Curie
(Paris, France)
Lake Louise Winter Institute (Canada) February
20-26, 2005
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Why Electroweak Measurements?

• Precise Electroweak predictions
• Challenge for Electroweak physics measurement
• Constrains the Standard Model
• OR
• Appearance of Physics Beyond SM
• Also crucial as input for LHC physics program
• Input to Parton Distribution Functions
• Some Tevatron signals will be LHC background
• After LEP era stepping into Tevatron era
• N(Z)_at_Tevatron gt N(W)_at_LEP

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Production Processes at Tevatron
Yield 104 Ws , 103 Zs

• Outline
• W and Z cross sections
• Asymmetries (W and Z)
• Diboson production
• W mass measurement

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W/Z Gauge Bosons and Event Topology
At hadron colliders Use clean leptonic decays
ETgt25GeV
W energetic lepton ET
Z energetic opposite sign leptons
PTmgt20GeV
PTmgt20GeV
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Inclusive W/Z Cross Sections
s(pp?Z)xBF(Z?ll)Th,NNLO251.35.0pb

• Good agreement with NNLO
• Systematics limited measurement
• Uncertainties Luminosity (6)
  
• PDFs(2)

s(pp?W)xBF(W?ln)Th,NNLO268754pb
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Indirect W Width Measurements
PDG
Checking internal consistency of SM with direct
G(W) measurement
R cross section measurement ratio
Many systematic uncertainties cancel
out(Luminosity)
Indirect W Width measurement
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W Asymmetry
Sensitivity to PDF distributions(u/d ratio) u
carries more momentum than d
Observable quantity is lepton rapidity Convolutio
n of W asymmetry and V-A interactions Charge ID
at high h is crucial Use of calorimeter
seeded tracks
?Ldt170pb-1
Asymmetry
Asymmetry
Larger ET electron direction closer to W
direction. Production asymmetry enhanced.
Lower ET decay asymmetry enhanced
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DiBoson Production

• Test Gauge Boson Self Interactions
• SM Higgs searches
• Resonance searches Look for excess in
  kinematical distributions ET(g) , 3body mass,
  lepton PT

Complementarity with LEP experiments Probing at
higher vs W-g final state
For Wg/Zg Photon Id is crucial Main
backgrounds p0?gg, jets faking photon Fake
Rates 0.2 _at_JetET10 GeV 0.05 JetETgt25GeV
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Wg Production
ET(g) Distribution
?Ldt200 pb-1
Baur, Han, Ohnemus(1993,1998)
CDF Run II
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Z-g Production
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Zg Kinematical Distributions
3Body Mass
ET(g) Distribution
BSM Predictions
Dk5 l5
Dk7 l0
No significant excess with respect to SM
expectations
Dk0 l3
SM
0 5 10 15 20 25 30 35 40 ET(g)
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WW Production
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WZ and ZZ Searches
Entangled Processes
s(pp?ZZ/ZWX)NLO5.00.4 pb-1
?Ldt 194pb-1
Extracted a limit for cross section Measurement
possible with available collected statistics
s(pp?ZZ/ZWX)CDFlt15.2 pb _at_95 C.L.
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W Boson Mass
Bound to SM Higgs Mass Indirect searches of
physics BSM Need accuracy better than 10-3 Fit of
transverse mass distribution G(W) direct
measurement Result With L200pb-1
DMW76 MeV/c2 (em) combined ?Already better than
RunI CDF With 2fb-1 expect D(Mw)30MeV/c2 Will
use next PDFs fits with CDF W charge asymmetry
measurement
Top Mass(GeV/c2)
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Perspectives and Working Areas

• Electroweak physics program at CDF goes well
• Inclusive cross section, widths, BF in all
  leptonic channels.
• Working on Differential Cross Sections
• Z asymmetries
• Quark gauge bosons couplings
• W asymmetries
• Shall be included in 2005 PDFs
• W Rapidity reconstruction
• Diboson production cross section (increase
  statistics)
• Extracting Triple Gauge Coupling
• Looking for hadronic final states WW?(qq)(lnl)
• W Boson Mass Measurement unveiling the central
  value
• Direct G(W) measurement

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O fortunati, quorum iam moenia surgunt! Verg.,
Aen., I 437
Electroweak RunII Publications hep-ex/0406078
Inclusive W and Z Cross Section hep-ex/0501023
W Charge Asymmetry hep-ex/0411059 Z Forward
Backward Asymmetry hep-ex/0410008 W gamma, Z
gamma production hep-ex/0501050 WW
Production hep-ex/0501021 WZ/ZZ Searches
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Backup Slides
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The Run II CDF Detector
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Tevatron Performances and Perspectives
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Z Boson Cross Sections(e,?)
Muon Channel PTmgt20 GeV/c
Electron Channel Electron hlt2.8 ETgt25 GeV
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20 Years of W and Z at hadronic colliders
NNLO
NNLO
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W Boson Production
Electron Channel
Muon Channel
?B(W--gten) (pb)
Region
Events
Bkg
278616stat64sys166lum
hlt1.0
37584
4.4
72
e
287434stat167sys172lum
8.7
10464
1.1lthlt2.8
64
m
194
57109
9.5
hlt1.0
278612stat65-55sys172lum
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Z Asymmetry
AFB arises from Axial and Vector couplings Z and
g interference term

• Measurement limited by statistics
• Complementary to LEP
• measurement far from the Z pole
• Sensitivity to heavy neutral bosons (Z')
• Extract quark, electron couplings and sin2qWEff

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Couplings Results
c210.40/11
Quark Couplings
sin2?WEff0.22380.0040(stat)0.0030(syst) c212.5
0/14
Electron Couplings
c213.14/13
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20 years of W and Z bosons at hadron colliders
From R to G(W)
Indirect W Width measurement
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Tau
Taus are difficult at hadronic colliders t?hadrons
(th) look like jets Need to combine Tracking
(hlt1) Calorimetric Clusters Dhx Df (0.1 x
15o) po reconstruction (showermax inside EM
Calorimeter resol. few mm) Reconstruction
Efficiency 70 _at_15 GeV 85 _at_25 GeV 95
_at_40 GeV It is possibile to trigger on
taus Lepton Track trigger (lepton isolated
track). Final statestht(e,m)X,th(e,m)X
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Tau Physics Measurement
Track Multiplicity 1 and 3 prongs
Z-gtteth
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Wg Production
q
?
l
ISR
CDF Run II
W
?
q'
l
WW?
q'
W
q
l
q'
?
W
FSR
q
?Ldt200 pb-1
Baur, Han Ohnemus(1993,1998)
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Z Asymmetry
CDF Run I (110 pb-1)
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Calculating AFB

• Calculating AFB

• cos? in Collin-Soper frame
• Minimize ambiguity in the incoming quark Pt
• cos?gt0 ?Forward
• cos?lt0 ?Backward

lab frame
Z0/g
PZ 0
Z-Axis
Z0/g
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Data-MC Comparisons
CDF II Preliminary
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Data-MC Cos(?)
CDF II Preliminary
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Couplings Results
Electron Couplings
c213.14/13
Quark Couplings
sin2TWEff Measurement
sin2?WEff0.22380.0040(stat)0.0030(syst) c212.5
0/14
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W Asymmetry
Anastasiou, Dixon, Melnikov, Petriello, Phys Rev
D 69, 094008 (2004)
Charge ID is crucial at high rapidity
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Raw Asymmetry

• Corrections to extract true asymmetry
• Charge misidentification rate.
• Background subtraction.
• Both bias the asymmetry low ? dilution.
• Measured in each ? bin.
• Uncertainties in corrections go directly in A.

Shape is convolution of A(yW) and V-A Sign
switch _at_ ??? gt 2
??? lt 1 linear
Curve is just to guide the eye.
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W Asymmetry
xf(x,Q2)
Run I Result
log(x)

• http//durpdg.dur.ac.uk/hepdata/pdf3.html

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Phoenix (Calorimeter-Seeded) Tracking

• Two points and a curvature
• define a helix
• Primary collision vertex position.
• Fitted position of calorimeter shower maximum.

Use both central and forward electrons! h lt 2.8
Zoom into Silicon
Phoenix SiTrack
Cal. Seed Tracks
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Wg production
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Wg
DR(g-l)
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Z-g
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Zg Production
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WW production
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WW-gtenmnm
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WW-gtenmnm or ZZ-gtee nn?
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W Boson Mass background
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W Boson Mass
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WW production Kinematical Distributions
Lepton PT
Dilepton Invariant Mass
No significant excess so far