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

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP2 W pair production Tree level scattering unitarity  electroweak renormalizability SU(2)  U(1) Gauge Cancellations We WW  WWZ

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP3 W pair events at LEP qq qq,We qq qq,Zee , ,ll bkg 75-80%80-90%qqqq 80-85%50-80%  qq ~95%75-90%  qq ~90% 75-90% e qq 80-90%50-80% l purity efficiencyChannel

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP4 Total cross section 4  700 pb -1 at GeV 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 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP5 Data 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 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP6 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.

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP7 WW spin correlations L3 - Eur.Phys.J.C40 (2005) 333 qql events only Measure fractions f +,f -,f 0 of W helicity states with the W rest frame lepton decay angle  * cos  W dependence of produced helicities select events with backw: 26% (0,0) forw: 69% ( ,  )

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP8 WW spin correlations qql events deplete/enhance hadr W helicity  with cuts on |cos  q * | Data CL to no spin correlations = 1% Data CL to KORALW SM = 35%

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP9 WW decay-plane correlations From both qqqq & qql events |  | distribution corrected for eff, bkg, wrong pairing

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP10 Spin density matrix OPAL - Phys.Lett.B585 (2004) 223 L3 - Phys.Lett.B557 (2003) 147 DELPHI 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 polarization  L =23.6  1.6% (SM 24%)

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP11 Z pairs productions In agreement with SM within 5% precision No gauge self couplings involved in Standard Model Z-pair production

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP12 Single W and Z events In agreement with SM within 8% precisionIn agreement with SM within 7% precision

Moscow 27/7/06 ICHEP06P.Azzurri - WW cross sections and spin correlations at LEP13 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) 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)