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Triple and Quartic Gauge Couplings at LEP 2

Triple and Quartic Gauge Couplings at LEP 2. Renaud Brunelière LAPP - Université de Savoie on behalf of the four LEP experiments. Outline. Triple gauge boson couplings (TGC) charged W + W  , W + W  Z neutral Z , ZZ, ZZZ Quartic gauge boson couplings (QGC) W + W  , W + W  Z,

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Triple and Quartic Gauge Couplings at LEP 2

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  1. Triple and Quartic Gauge Couplings at LEP 2 Renaud Brunelière LAPP - Université de Savoie on behalf of the four LEP experiments Gauge Couplings at LEP2

  2. Outline • Triple gauge boson couplings (TGC) • charged W+W, W+WZ • neutral Z, ZZ, ZZZ • Quartic gauge boson couplings (QGC) W+W, W+WZ, ZZ, W+WZZ, W+WW+W present in SM not in SM Gauge Couplings at LEP2

  3. Gauge Boson Couplings Why do we measure gauge boson couplings ? • Test of the non-Abelian nature of the electroweak sector • Probe for new physics at higher energies How ? Use an effective Lagrangian • modify existing SM couplings • introduce non-SM couplings  Anomalous couplings Gauge Couplings at LEP2

  4. W+ W+  Z W W • At LEP2 • C and P invariance • U(1)Q • SU(2)LU(1)Y Charged Triple Gauge Boson Couplings • Generally K. Hagiwara et al. Nucl.Phys. B282 (1987) 253-307 7 parameters 7 parameters (at tree level) V = Z,  Gauge Couplings at LEP2

  5. Physics processes • e+e W+W (CC03) • e+e Wene 188.6 GeV =15.980.23 pb 188.6 GeV =0.600.09 pb g1Z, kg and lg kg and lg • e+e nene Gauge Couplings at LEP2

  6. Cross-section • Quadratic behaviour : g = anomalous coupling • Single W production useful for  Gauge Couplings at LEP2

  7. lqq • most of the information in W • no flavor tagging • W charge tagging in WW qqqq channel (80%) e+e W+W Kinematic : 5 angles OPAL PR381 Gauge Couplings at LEP2

  8. e+e  Wee • qqee : Angle between the two jets, total transverse momemtum, NN output • llee: El, cos l, PT(lepton) ALEPH We WW ZZ Gauge Couplings at LEP2

  9. New results from L3 including W+W qqqq & year 2000 for We. • Update of results from ALEPH • Final results from OPAL for WW pair production. 1D results The other two couplings are set to their SM value • Existence of triple gauge couplings is proven. • Compatible with the Standard Model expectations. • Sensitive to radiative corrections (102) SM 1 0 1 Gauge Couplings at LEP2

  10. Systematics Systematic sources correlated between experiments : • e+e W+W • Theory uncertainty on the cross-section (0.5%) • Theory uncertainty on angular distributions (YFSWW-RacoonWW) • Fragmentation • Color reconnection • Bose-Einstein correlations • e+e  Wee • Theory uncertainty on the cross-section (5%) Gauge Couplings at LEP2

  11. 2D results ln(L) = 0.5 The third coupling is set to its SM value. Gauge Couplings at LEP2

  12. CP violating couplings • Measurement of all CP-violating trilinear couplings separately. • Analysis done with WW pairs (183  207 GeV) - ALEPH data only. • For CP-conserving couplings, see • Alternative approach : spin density method, see next talk. Good agreement with SM expectations ALEPH 2003-035 Gauge Couplings at LEP2

  13. For , at 95% C.L. Techni- form factor Vector Resonance Enhancement of New T.L.Barklow et al. “Strong Electroweak Symmetry Breaking” hep-ph/9704217 ALEPH data only White region is excluded at 95% CL. Gauge Couplings at LEP2

  14. Z* * Z* * * Z* Z* Z* Z* e+e  Z e+e  ZZ *Z, Z* Z *ZZ, Z* ZZ Neutral Triple Gauge Boson Couplings At LEP2 : we assume final bosons are on-shell 15 CP-conserving forms +29 CP-violating forms G.J.Gounaris, J.Layssac, F.M.Renard. Phys.Rev. D62(2000) 073013 We separate f couplings h couplings Gauge Couplings at LEP2

  15. CP - violating CP - conserving e+e  *  Z, e+e  Z*  Z • Anomalous couplings • Standard model Standard Model at tree level: Loop corrections : Gauge Couplings at LEP2

  16. Observables • Cross-section • Shape • |cos()|, E , ,jet • Optimal observables G. Abbiendi et al., Eur. Phys. J. C17 (2000) 13. Gauge Couplings at LEP2

  17. 1D results (1/2) *Z 95% CL CP-violating CP-conserving • Update of results from L3 Gauge Couplings at LEP2

  18. 95% CL 1D results (2/2) Z*Z CP-violating CP-conserving Gauge Couplings at LEP2

  19. 2D results Correlation Correlation 79% 77% 97% 76% Gauge Couplings at LEP2

  20. CP - violating CP - conserving e+e  *  ZZ, e+e  Z*  ZZ • Anomalous couplings • Standard model Standard Model at tree level: Loop corrections : 188.6 GeV =0.660.07 pb Gauge Couplings at LEP2

  21. Coupling extraction • Cross-section • Shape : • cos(Z) • Optimal observables DELPHI 2001-097 OPAL PN482 Gauge Couplings at LEP2

  22. 1D results *ZZ Z*ZZ 95% CL CP-violating CP-conserving • Final results from L3, OPAL Gauge Couplings at LEP2

  23. W+ W+ Z    W W Z Z   Quartic Gauge Boson Couplings G.Bélanger, F.Boudjema. Phys.Lett. B288(1992) 201. W.J.Stirling, A.Werthenbach. Phys.Lett. C14(2000) 103. Gauge Couplings at LEP2

  24. Physics processes • Anomalous couplings • Main diagrams • Coupling extraction Cross-section + missing mass, E2, max(|cos(1)|, |cos(2)|) Cross-section + E , cos() Gauge Couplings at LEP2

  25. Signature : 2 acoplanar photons • Photon definition (OPAL) : • E > 10 GeV • |cos | < 0.9 • Coupling extraction : missing mass, E2 ALEPH 2003-009 OPAL PN510 Gauge Couplings at LEP2

  26. Cross-section • Signal definition : For each photon • E > 5GeV • |cos()|<0.97 (L3), |cos()|<0.95 (OPAL) • cos(q)<0.98 (L3), cos(q)<0.90 (OPAL) Invariant mass window • |s’  mz| < 2Z (L3) • 80 GeV < Mqq < 120 GeV (OPAL) Phys. Lett. B540/1-2 (2002) 43 Gauge Couplings at LEP2

  27. Shape : • E2 = energy of the least energetic photon • max(|cos(1)|, |cos(2)|) Phys. Lett. B540/1-2 (2002) 43 Gauge Couplings at LEP2

  28. Shape • Cross-section Signal = E>5 GeV, |cos |<0.95 cos f<0.90, |Mff’  MW| < 2W SM DELPHI 2003-059 Gauge Couplings at LEP2

  29. New results from ALEPH for  • Final results from OPAL with WW WW, WWZ • No LEP combination 95% CL ALEPH DELPHI L3 OPAL • All results in GeV-2 Gauge Couplings at LEP2

  30. New results from ALEPH for  ZZ 95% CL • All results in GeV-2 Gauge Couplings at LEP2

  31. Summary • Charged triple gauge boson couplings are measured (precision  10-2) using WW, single W productions • Neutral triple gauge boson couplings are studied with Z and ZZ events. Precision  10-2 - 10-1 • Quartic gauge boson couplings are measured with WW, qq and  events. Precision  10-2 • In all these channels no significant deviations from Standard Model expectations are found. • Wait for current and next colliders : Tevatron, LHC, NLC Gauge Couplings at LEP2

  32. 2D results, ZZ channel Correlation 2% -18% Gauge Couplings at LEP2

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