Electroweak Results from D

1
Electroweak Results from DØ

• Bob Olivier
• LPNHE Paris
• on behalf of the DØ collaboration

• W Mass Measurement
• W/Z production cross-sections
• W Width determination
• Trilinear Gauge Couplings
• QCD effects in W/Z production

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W and Z in pp collisions
QCD cross-section dominates gtselection based
on leptonic decays only
p
l
q
W,Z
p
l,nl

• W selection
• isolated lepton (e,m,t) ET gt 15 25 GeV
• neutrino(n) ET gt 25 GeV

• Z selection
• 2 isolated leptons (ee,mm) ET gt 15 25 GeV
• Looser criteria on 2nd lepton

Data Samples Run 1a L15 pb-1 Run 1b L90
pb-1
?h? lt 1, 1.5 lt ?h? lt2.5
electron channel
W candidates 67078 Z candidates
5397
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Measurement of MW

• Radiative corrections DrW to MW depend on MH
• Consistency check of SM

• Measured Quantities

• No longitudinal momentum
• conservation due to particles
• escaping in the beam pipe
• MW from fit to

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DØ MW with e at large rapidity
EC
CC
EC
CC
EC
EC

• h(W) sensitive to pdfs and correlated to h(e)
• Good agreement with MRST used for MC
  description

• Calibration from
• ? adjusted to LEP value
• in CC-EC and EC-EC
• Z statistics is dominant
• error

DMW 181 MeV (EC) DMW 59 MeV (CCEC)
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DØ MW Results
MT fit

• MW from fit to MT (W)

Combined CCEC
Fit window
pT (e) fit

• MW from fit to pT (e)

Combined CCEC
pT (n) fit

• MW from fit to pT (n)

Combined CCEC
Combined results from Run 1b Combined results
from Run 1a, 1b
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MW World Average

• Good agreement hadronic leptonic colliders
• World average precision on MW 38 MeV

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Constraints on MHiggs

• CDF and DØ DMW 63 MeV
• Constraints on MH from MW Mtop

8
W,Z cross-sections
for e,m,t decays
CDF and DØ use different
for luminosity determination

• CDF DL 4.1
• (CDF measurement only)
• DØ DL 4.4
• (CDF, E710, E811)

?
Run 1c _at_
_at_
in good agreement with UA1/UA2
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Lepton Universality t - e
Ratio of from cross-section ratio
Errors in luminosity cancel in ratio
?
World average verifies e-t Universality at 2.5
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Branching Ratio B(W ? en)
Theory ( 1.5)
LEP ( 0.2)
extracted
measured
Branching Ratio at 2.5 from Tevatron
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Indirect Determination of G(W)
Theory ( 0.4)
Theory ( 1.5)
LEP ( 0.2)
extracted
measured
DØ 95 C.L. on invisible W-width 0.191 GeV
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Trilinear Gauge-Boson Couplings
WW production
WZ production

• Trilinear couplings

• In SM lZ lg 0 , kZ kg g1Z g1g 1

prevents unitarity violation at low scale
?

• Constrain trilinear gauge boson couplings
• look for indications of new physics.

?
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WW/WZ in channel

• pt(W) spectrum sensitive to
• anomalous coupling
• (DkV for lV 0)

• Fit to pt(en) and pt(mn)
• assuming equal
• WWg and WWZ couplings

• 95 CL at LFF 2 TeV

mnjj
enjj
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WZ in tri-lepton channel

• WZ production is sensitive to WWZ coupling only,
• independent of WWg coupling
• Search in enee and mnee channels 1 candidate
  event
• ? SM prediction 0.245 0.015 events
• ? Backgrounds 0.50 0.15 events

• Limits at 95 C.L.

l lt 1.42, D gZl lt 1.63
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Limits on TGC
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W Angular Decay Distribution
QCD corrections
V-A
V-AQCD
QCD corrections prefered at 2 s
(Systematic errors 6-15)
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pt dependence of s(Z)

• Sensitivity to gluon radiation in ds(Z)/dpt
• ptgt10 GeV perturbative QCD
• ptlt10 GeV resummation techniques
• pt ? 0 parametrization of non-perturbative
  effects

NNLO-QCD calculation From RESBOS with CTQ4M
pdf In good agreement with ds(Z)/dpt
DØ

• Low pt fit of Sudakov form factor

Ladinsky -Yuan form factor g20.59 0.06
GeV2 g10.09 0.03 GeV2 g3-1.1 0.06 GeV-1
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Conclusions - Outlook

• SM in good agreement with high precision EW
  measurements
• Precision on MW better than 100 MeV Run2
  prospectives
• 15fb-1 from 2001 to LHC
• 2fb-1 in first 2 years
• and improved detectors (tracking)

?
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Backup Slides
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pt dependence of s(Z)

• Sensitivity to gluon radiation in ds(Z)/dpt
• ptgt10 GeV perturbative QCD
• ptlt10 GeV resummation techniques
• pt ? 0 parametrization of non-perturbative
  effects

? form factor

• High and medium pt range

NLO-QCD calculation pT resummation from RESBOS
with CTQ4M pdf
DØ
Data vs ResBos
In good agreement with ds(Z)/dpt
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Extraction of non-perturbative parameters

• Low pt range fit of Sudakov form factor from
• Ladinsky and Yuan

most sensitive
from low-energy Drell-Yan data and CDF Z event
sample (1988-89)

• New extraction of g2

g2 0.59 ? 0.06 GeV2
In good agreement and more precise than previous
measurement
D0 also extracts g1 0.09 ? 0.03 GeV2
g3 -1.1 ? 0.6 GeV-1
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Recent LEP limits on TGC