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WW cross section and spin correlations at LEP

WW cross section and spin correlations at LEP. P.Azzurri SNS-Pisa Moscow July 27 2006. XXXIII International Conference on High Energy Physics Electroweak Physics. We . WW . WWZ. W pair production. SU(2) U(1) Gauge Cancellations.

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WW cross section and spin correlations at LEP

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  1. WW cross section and spin correlations at LEP P.Azzurri SNS-Pisa Moscow July 27 2006 XXXIII International Conference on High Energy Physics Electroweak Physics

  2. We WW WWZ W pair production SU(2)U(1) Gauge Cancellations Tree level scattering unitarity  electroweak renormalizability P.Azzurri - WW cross sections and spin correlations at LEP

  3. Channel efficiency purity bkg ll 50-80% 80-90% ,,ll eqq 75-90% qq,Zee ~90% qq 75-90% ~95% qq qq 50-80% 80-85% qq,We qqqq 80-90% 75-80% qq W pair events at LEP P.Azzurri - WW cross sections and spin correlations at LEP

  4. Total cross section 4700 pb-1 at 161-209 GeV OPAL final paper is coming Clear proof of SU(2)xU(1) gauge couplings ! Combination 2=26.6/24 Hadronization uncertainty is largest common systematic (0.6% error) Threshold mass P.Azzurri - WW cross sections and spin correlations at LEP

  5. Data vs Theory • Theory uncertainty: • ~2%(161GeV) • 0.7%(170GeV) • 0.4%(200GeV) Experimental precision better than 1% Test of the SM radiative corrections to the CC03 diagrams (~3% effects) P.Azzurri - WW cross sections and spin correlations at LEP

  6. cosW- 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. P.Azzurri - WW cross sections and spin correlations at LEP

  7. WW spin correlations L3 - Eur.Phys.J.C40 (2005) 333 qql events only cosW dependence of produced helicities select events with forw: 69% (,) backw: 26% (0,0) Measure fractions f+,f-,f0 of W helicity states with the W rest frame lepton decay angle * P.Azzurri - WW cross sections and spin correlations at LEP

  8. WW spin correlations deplete/enhance hadr W helicity  with cuts on |cosq* | qql events Data CL to no spin correlations = 1% Data CL to KORALW SM = 35% P.Azzurri - WW cross sections and spin correlations at LEP

  9. WW decay-plane correlations From both qqqq & qql events || distribution corrected for eff, bkg, wrong pairing P.Azzurri - WW cross sections and spin correlations at LEP

  10. Spin density matrix OPAL - Phys.Lett.B585 (2004) 223 L3 - Phys.Lett.B557 (2003) 147 DELPHI - 2004-018 CONF 693 W-pair SDM extract W helicities from angular distributions of decay products / fit to SDM elements W longitudinal polarization L=23.61.6% (SM 24%) Direct limits on CP-violating TCG couplings P.Azzurri - WW cross sections and spin correlations at LEP

  11. Z pairs productions No gauge self couplings involved in Standard Model Z-pair production In agreement with SM within 5% precision P.Azzurri - WW cross sections and spin correlations at LEP

  12. Single W and Z events In agreement with SM within 8% precision In agreement with SM within 7% precision P.Azzurri - WW cross sections and spin correlations at LEP

  13. Summary 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) P.Azzurri - WW cross sections and spin correlations at LEP

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