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

2. W and Z in pp collisions QCD cross-section p dominates
=>selection based on
leptonic decays only l q q’
W,Z p
l,nl
W selection:
isolated lepton (e,m,t): ET > 15 – 25 GeV
neutrino(n): ET > 25 GeV
Z selection:
2 isolated leptons (ee,mm) : ET > 15 – 25 GeV
Looser criteria on 2nd lepton
Data Samples:
Run 1a: L~15 pb Run 1b: L~90 pb-1
h < 1, < h <2.5
electron channel
W– candidates:
Z – candidates:
April 17-19, 2000
Bob Olivier - PHENO2000

3. 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:
April 17-19, 2000
Bob Olivier - PHENO2000

4. DØ: MW with e at large rapidityEC CC EC EC CC EC
h(W) sensitive to pdf’s 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 (CC+EC)
April 17-19, 2000
Bob Olivier - PHENO2000

5. DØ: MW Results MT fit MW from fit to MT (W): Combined CC+EC:
window
pT (e) fit
MW from fit to pT (e):
Combined CC+EC:
pT (n) fit
MW from fit to pT (n):
Combined CC+EC:
Combined results from Run 1b:
Combined results from Run 1a, 1b:
April 17-19, 2000
Bob Olivier - PHENO2000

6. MW : World Average Good agreement hadronic & leptonic colliders
World average precision on MW =38 MeV
April 17-19, 2000
Bob Olivier - PHENO2000

7. Constraints on MHiggs CDF and DØ DMW = 63 MeV
Constraints on MH from MW ~ Mtop
April 17-19, 2000
Bob Olivier - PHENO2000

8. W,Z cross-sections for e,m,t decays Run 1c @ CDF and DØ use
different for
luminosity determination
CDF: DL = 4.1%
(CDF measurement only)
DØ: DL = 4.4%
(CDF, E710, E811) 
Run @
in good agreement with
UA1/UA2
April 17-19, 2000
Bob Olivier - PHENO2000

9. 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%
April 17-19, 2000
Bob Olivier - PHENO2000

10. Branching Ratio B(W  en)
measured
Theory
(± 1.5%)
LEP
(± 0.2%)
extracted
Branching Ratio at 2.5% from Tevatron
April 17-19, 2000
Bob Olivier - PHENO2000

11. Indirect Determination of G(W)
Theory (± 0.4%)
measured
Theory
(± 1.5%)
LEP
(± 0.2%)
extracted
DØ : 95% C.L. on invisible W-width GeV
April 17-19, 2000
Bob Olivier - PHENO2000

12. 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. 
April 17-19, 2000
Bob Olivier - PHENO2000

13. 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:
April 17-19, 2000
Bob Olivier - PHENO2000

14. 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: ± events
 Backgrounds: 0.50 ± 0.15 events
Limits at 95% C.L. :
|l| < 1.42, |D gZl | < 1.63
April 17-19, 2000
Bob Olivier - PHENO2000

15. Limits on TGC
April 17-19, 2000
Bob Olivier - PHENO2000

16. W Angular Decay Distribution
QCD corrections: W g q q’ q sq
V-A
V-A: q sq sW
QCD
V-A+QCD:
QCD corrections
prefered at ~2 s
(Systematic errors
6-15%)
April 17-19, 2000
Bob Olivier - PHENO2000

17. pt dependence of σ(Z) Sensitivity to gluon radiation in dσ(Z)/dpt
pt>10 GeV: perturbative QCD
pt<10 GeV: resummation techniques
pt  0 : parametrization of non-perturbative effects
NNLO-QCD calculation
From RESBOS with
CTQ4M pdf
In good agreement with
dσ(Z)/dpt DØ
Low pt: fit of Sudakov form factor
Ladinsky -Yuan
form factor:
g2=0.59 ± 0.06 GeV2
g1=0.09 ± 0.03 GeV2
g3=-1.1 ± 0.06 GeV-1
April 17-19, 2000
Bob Olivier - PHENO2000

18. 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) 
April 17-19, 2000
Bob Olivier - PHENO2000

19. Backup Slides
April 17-19, 2000
Bob Olivier - PHENO2000

20. pt dependence of σ(Z) Sensitivity to gluon radiation in dσ(Z)/dpt
pt>10 GeV: perturbative QCD
pt<10 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
dσ(Z)/dpt
April 17-19, 2000
Bob Olivier - PHENO2000

21. 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
( )
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
April 17-19, 2000
Bob Olivier - PHENO2000

22. Recent LEP limits on TGC
April 17-19, 2000
Bob Olivier - PHENO2000