Electroweak measurement

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Electroweak measurement _at_ the Tevatron
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Tevatron, CDF and DØ

• P-Pbar _at_1.96 TeV, 2x1032 cm-2s-1
• Vector boson factor L 30 pb-1/week
• 0.7 million W,
• 0.15 million Z
• 400 WW, 120 WZ, 50 ZZ,
• Precise test on Standard Model understand Higgs
  background
• Two experiments perform with high efficiency

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Single W and Z production
-- Due to large jet background, W and Z events
are typically reconstructed in lepton decay le,m
-- Tools to calibration isolated high pT
le,m and MET from W?en -- Physics
NNLO QCD test on Z pT, h distribution, Z?tt, and
MW measurement etc and something that wont be
accessible at LHC
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W charge asymmetry
-- Up quarks carry more proton momentum than
down quarks ? more W- in anti-proton direction,
and more W in proton direction
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Lepton and W charge asymmetry

• DØ, W?l? lepton charge asymmetry
• CP folding ? -A(-y)A(y)

-- Experimental uncertainties have already been
smaller than or comparable with the parton
distribution function CTEQ uncertainties in most
regions
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Z/g?ll- Forward/Backward Asymmetry

• Standard Model neutral-current couplings of Z
  bosons to fermions as

-- ? as negatively charged e- relative to the
incoming quark
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• Tevatron, the only place of qqbar?e-e AFB
  precise measurement

• Many systematic uncertainties cancelled

• Complementary sensitivity to Z
  model-independently, via Z/g/Z interference

• Precise test on the SM, especially the weak
  mixing angle sin2qW measurement

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• SM fundamental parameters a, GF, MZ, MW and
  sin2qW

• The effective weak mixing angle
  , from Z-pole observables, e.g.
  AFB

-- NuTeV n-N scattering 0.22770.0016, 3.1s
from SM prediction PRL 88, 091802(02)
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_at_ Tevatron

• DØ 1fb-1 analysis

0.23270.00180.0006
(statistic) (systematic)
-- systematic 0.0005 CTEQ6 PDF
0.0003 EM scale/resolution
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Unfolded AFB distribution _at_ Tevatron

• Correct detector resolution, acceptance
  efficiency etc ? comparable to prediction

• Detector resolution ? Mee migration ? unfolding
  matrix, computed iteratively on rewighted MC

• Detector geometric and kinematic cuts ? correct
  acceptance efficiency

-- Provide complementary information on heavy Z
boson search
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Di-Boson production

• Wg (DØ 0.7 fb-1)
• Zg (DØ 1 fb-1)
• WZ (CDF 2 fb-1, DØ 1 fb-1)
• WW/WZ ?l?jj (CDF 1.2 fb-1)
• ZZ (CDF 2 fb-1, DØ 1 fb-1)

• Precise test of non-Abelian SU(2)LU(1)Y
• -- complementary to LEP higher c.m.
  energy, new couplings of charged currents
• Probe TGC (trilinear gauge couplings)
• -- sensitive to low energy remnants of
  new physics _at_ high scale
• Background to hunting Higgs, top and SUSY
• Topology 2 isolated high pT(gt15 GeV)
  lepton(le,m)/g, MET(gt20 GeV) for W

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WZ production _at_ Tevatron
SM NLO
PRD 60, 113006 (1999)

• Unique measurement on WWZ TGC

• WZ?llln search channel

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Evidence of WZ?3l _at_ DØ 1fb-1

• 13 candidates with 4.5 background 3?
  significance

(HWZ generator)

• Anomalous WWZ TGC

?1.5 TeV ?2.0
TeV a -0.18lt?Zlt0.22
-0.17lt?Zlt0.21 -0.15lt?g1Zlt0.35
-0.14lt?g1Zlt0.34 -0.14lt??Z ?g1Z lt0.31
-0.12lt??Z ?g1Z lt0.29
PRD 76, 111104(R) (2007)
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Observation of WZ?3l _at_ CDF 2fb-1

• Cross-section measurement 25 candidates

PRL 98, 161801

• Constraint on anomalous WWZ

?1.5 TeV ?2.0 TeV a
-0.14lt?Zlt0.16 -0.13lt?Zlt0.14
-0.17lt?g1Zlt0.27 -0.15lt?g1Zlt0.24
-0.86lt??Zlt1.36 -0.82lt??Zlt1.27
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WW/WZ?lnjj _at_ CDF 1.2fb-1

• First measurement of (lMET2jets) _at_Tevatron

• more statistic? sensitive to TGC
• similar to WH?lnbb
• huge background from Wjets, 300pb

s(WWWZ)Br 2.090.14 pb

• Analysis strategy

1) NN to increase S/B significance
2) likelihood fit ? signal fraction
?xBr lt 2.88 pb_at_95C.L.
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Radiation-Amplitude Zero in Wg

• SM RAZ (Radiation Amplitude Zero)

• Measured as Charge-Sign photon-lepton Rapidity
• Difference Q??(?) - ?(l)

dip
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Study of W(ln)g RAZ _at_ DØ 0.7fb-1

• First indication of RAZ

ET(g)gt7GeV, ?R(l?)gt0.7, MT(lgn)gt90GeV

• Full covariance matrix c2/dof17.0/12
• 2-Bin Statistical analysis
• unimodal hypothesis ruled out _at_ 2.6 s

Small Max Bin
Dip Bin

• Photon pT spectrum ? anomalous WWg TGC

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Precise Z(ll)g measurement _at_ DØ 1fb-1

• Event selections

ET(g)gt7GeV, ?R(l?)gt0.9, M(ll)gt30GeV
?( Zg?llg ) 4.96 0.30(statsyst)0.30(lumi) pb.
SM NLO 4.74 0.22 pb. PRD 57, 2823 (1998)
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Anomalous ZZg/ Zgg TGC_at_ DØ 1fb-1

• Photon ET spectrum of selected events

PLB 653, 378 (2007)
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First measurement of ZZ _at_ CDF 2fb-1

• Charged 4l channel
• 3 events with 0.1 background ? 4.2 ? significance

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• Combined 4l llnn result 4.4 ? significance

SM NLO 1.4 0.1 pb. PRD 60, 113006 (1999)
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Search for ZZ _at_ DØ

• SM NLO
• --1.6 ? 0.1pb PRD 62, 113011 PRD 60,
  072002
• -- t-channel only, no tri-linear TGC

• Charged 4l channel _at_1 fb-1 M(ll) gt 30 GeV for
  eeee, eemm, mmmm

hep-ex/0712.0599
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• Combined e and m channel of llnn _at_ 2.2 fb-1

• Recoil of ZX ? discriminating variable

• Physics background ? likelihood

muon channel

• Statistic test 1.77 s significance predicted ?
  2.4 s significance observed

• Cross section measurement

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EW Physics _at_ Tevatron

• Precise measurement from O(104)pb
• down to O(1)pb _at_ up to 2fb-1,
• precise agreement to SM is observed

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Backup slides
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Integral Luminosity
-- Collider performance
-- Experiment performance
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Z??? inclusive cross section

• DØ (1 fb-1) Z??(??)?(?hadron)
• 1527 candidates with 20 backgrounds
• ? (pp?Z)xBr(Z???) 247 8(stat.) 13(syst.)
  15(lumi.) pb
• Consistent with SM prediction 251.95-11.8 pb
• Experimentally important for all ? studies such
  as H??? search

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