ww cross section and spin correlations at lep p.azzurri sns-pisa moscow july 27 2006 p.azzurri...
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WW cross section and spin correlations at LEP
WW cross section and spin correlations at LEP
P.Azzurri SNS-PisaMoscow July 27 2006P.Azzurri SNS-Pisa
Moscow July 27 2006
XXXIII International Conference on High Energy Physics
Electroweak PhysicsElectroweak Physics
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 2
W pair productionW pair production
Tree level scattering unitarity electroweak renormalizability
SU(2)U(1) Gauge Cancellations
We
WW
WWZ
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 3
W pair events at LEPW pair events at LEP
qq,Weqq
qq,Zee
,,ll
bkg
75-80%80-90%qqqq
80-85%50-80%qq
~95%75-90%qq~90%75-90%eqq
80-90%50-80%llpurityefficiencyChannel
W 1 3
W qq ' 2 3
WW (~ 10%)
WW qq ' (~ 45%)
WW qq 'qq ' (~ 45%)
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 4
Total cross sectionTotal cross section
4700 pb-1 at 161-209 GeV
mW 80.40 0.21 GeV/c 2
Clear proof of SU(2)xU(1)
gauge couplings !
Combination 2=26.6/24
Threshold mass
Hadronization uncertainty is largest common systematic (0.6% error)
OPAL final paper is coming
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 5
Data vs TheoryData vs Theory
Test of the SM radiative
corrections to the CC03 diagrams (~3%
effects)
Experimental precision
better than 1%
Theory uncertainty:• ~2%(161GeV) • 0.7%(170GeV) • 0.4%(200GeV)
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 6
cosW- distributioncosW- distribution
Combined for possible future test of new theoretical models
qqe and qq channels only,
four energy bins
Identical 4f contributions reduced with additional cuts on the lepton
direction (||>20), then subtracted.
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 7
WW spin correlations WW spin correlations L3 - Eur.Phys.J.C40 (2005) 333
qql events only
Measure fractions f+,f-,f0 of W helicity states with the W rest frame lepton decay angle *
cosW dependence of produced helicities select events with
0.9 cosW 0.3
0.3 cosW 0.9
backw: 26% (0,0)
forw: 69% (,)
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 8
WW spin correlations WW spin correlations
qql events
deplete/enhance hadr W helicity with cuts on |cosq*
|
Data CL to no spin correlations = 1%Data CL to KORALW SM = 35%
cosq 1 3
cosq 2 3
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 9
WW decay-plane correlations WW decay-plane correlations
From both qqqq & qql events
|| distribution corrected for
eff, bkg, wrong pairing
D 0.012 0.0210.012
KORALW
D 0.010 0.002
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 10
Spin density matrixSpin density matrixOPAL - Phys.Lett.B585 (2004) 223
L3 - Phys.Lett.B557 (2003) 147DELPHI - 2004-018 CONF 693
extract W helicities from angular distributions of decay products / fit to SDM elements
W-pair SDM
Direct limits on CP-violating TCG couplings
W longitudinal polarizationL=23.61.6% (SM 24%)
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 11
Z pairs productionsZ pairs productions
In agreement with SM within 5% precision
No gauge self couplings involved in Standard Model Z-pair production
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 12
Single W and Z eventsSingle W and Z events
In agreement with SM within 8% precisionIn agreement with SM within 7% precision
Zeeee Weee
Moscow 27/7/06 ICHEP06 P.Azzurri - WW cross sections and spin correlations at LEP 13
SummarySummary
1% accurate measurement of W-pair cross section has yielded the first direct and precision confirmation of the
electroweak SU(2)U(1) structure
Nice measurements of W polarizations, spin and decay plane correlations, and spin density matrix (TGC related)
All LEP2 4f productions in good agreement (1-10%) with the Standard Model prediction
Marginal changes expected for the final combination of results (very soon)
1% accurate measurement of W-pair cross section has yielded the first direct and precision confirmation of the
electroweak SU(2)U(1) structure
Nice measurements of W polarizations, spin and decay plane correlations, and spin density matrix (TGC related)
All LEP2 4f productions in good agreement (1-10%) with the Standard Model prediction
Marginal changes expected for the final combination of results (very soon)
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