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

2. R. Brunelière 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

3. R. Brunelière 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

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

5. R. Brunelière Gauge Couplings at LEP2 5 Physics processes e + e   W + W  (CC03)e + e   We e   and  g 1 Z,   and  188.6 GeV  =15.98  0.23 pb 188.6 GeV  =0.60  0.09 pb e + e    e e

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

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

8. R. Brunelière Gauge Couplings at LEP2 8 e + e   We e  qqe e : Angle between the two jets, total transverse momemtum, NN output  l l e e : E l, cos  l, P T (lepton) WW ZZ We ALEPH

9. R. Brunelière Gauge Couplings at LEP2 9 1D results  Existence of triple gauge couplings is proven.  Compatible with the Standard Model expectations.  Sensitive to radiative corrections (  10  2 ) SM 1 0 1  The other two couplings are set to their SM value 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.

10. R. Brunelière 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%)

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

12. R. Brunelière 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

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

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

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

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

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

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

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

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

21. R. Brunelière Gauge Couplings at LEP2 21 Coupling extraction Cross-sectionShape : –cos(  Z ) –Optimal observables OPAL PN482 DELPHI 2001-097

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

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

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

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

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

27. R. Brunelière 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

28. R. Brunelière Gauge Couplings at LEP2 28 SM DELPHI 2003-059 Cross-sectionShape Signal = E  >5 GeV, |cos   |<0.95 cos   f <0.90, |M ff’  M W | < 2  W

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

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

31. R. Brunelière 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

32. R. Brunelière Gauge Couplings at LEP2 32 2D results, ZZ channel Correlation2%-18%