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Anomalous Triple Neutral & Quartic Gauge Boson Couplings

Anomalous Triple Neutral & Quartic Gauge Boson Couplings. Stephan Wynhoff, Princeton University for the LEP collaborations. 31 st International Conference on High Energy Physics Amsterdam – July 24 th -31 st 2002. Introduction.

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Anomalous Triple Neutral & Quartic Gauge Boson Couplings

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  1. Anomalous Triple Neutral & Quartic Gauge Boson Couplings Stephan Wynhoff, Princeton Universityfor the LEP collaborations 31st International Conference on High Energy Physics Amsterdam – July 24th-31st 2002

  2. Introduction • Non-abelian structure of Standard Model  couplings between gauge bosons • Triple couplings • gWW, ZWW • ZZZ, ZZg, Zgg • Quartic couplings • WWgg, WWZg, • ZZgg, • WWZZ, WWWW real EW-3-4 don’t exist (at tree level) negligible at LEP don’t exist (at tree level) not at LEP

  3. Introduction (2) • Standard Model – nothing to expect • New Physics parameterized witheffective Lagrangian • enhancing existing couplings • introduce non-SM couplings Anomalous Couplings

  4. e- e- Z/g Z/g e e e+ e+ Z Z Neutral Triple Gauge Couplings Standard Model Anomalous Couplings Z/g • Vertex described by 12 parameters • Most general Lagrangian assuming • Lorentz invaricance • U(1)em invariance • Bose symmetry e- Z*/g* e+ Z

  5. g g h1 h2 g g h3 h4 Z Z Z Z h3 h1 h4 h2 Z Z e- e- g g f4 f5 Z Z f4 f5 Z*/g* Z*/g* e+ e+ Z Z Neutral Triple Gauge Couplings (2) G.J.Gounaris, J.Layssac, F.M.RenardPhys.Rev. D62(2000) 073013 CP - violating CP - conserving g g e- e- Z*/g* Z*/g* e+ Z e+ Z all values zero at tree level in Standard Model

  6. g g f4 f5 Z Z f4 f5 e+e-g*  ZZ, e+e- Z*  ZZ Use s, |cos qZ|, Neural Net, Optimal Observ. new since summer 2001 limits @95% CL

  7. g g h1 h2 g g h3 h4 e+e- g*  Zg, e+e- Z*  Zg Use s, |cos qg|,Eg, Optimal Observ. e+e- qqg, nng unchanged since summer 2001 limits @95% CL

  8. Z Z Z Z h1 h3 h2 h4 g*Zg, Z*Zg Measurements (2) unchanged since summer 2001 limits @95% CL

  9. g*Zg, Z*Zg Measurements (3) unchanged since summer 2001

  10. Quartic Gauge Couplings Non-abelian structure: Effective Lagrangian to parameterize New Physics L – energy scale for New Physics

  11. e+e-WWg W-pairs & hard, isolated photons • Signal definition • Eg> 5 GeV • |cos(qg)| < 0.95 • cos(a) < 0.90 (angle g – charged fermion) • |m(f,f’) –mW| < 2GW NEW Delphi, L3: Semi-leptonic & hadronic events Delphi 2002-059 Phys.Lett. B527/1-2 (2000) 29

  12. WWg Measurements Determination of anomalous couplings Fit to photon spectrum Delphi Phys.Lett B471 (1999) 293 SM an /L2 = -0.16 GeV-2

  13. -   e+ Z   e- e+e- nngg Signature: 2 acoplanar photons & missing energy CERN-EP 2002/033

  14. e+e- nngg Opal fits couplingsWWgg & ZZgg Estimations ofa0 /2,ac/2obtained looking for anomalous increase Opalprelim. OPAL-PN510

  15. /2 an /2 W W W W a0 ac ac a0 -0.031 GeV-2< a0/2 < 0.030 GeV-2 Summer 2001LEP combination -0.069 GeV-2< ac/2 < 0.070 GeV-2 -0.45 GeV-2< an/2 < 0.41 GeV-2 , , an /2 WWg209GeV WWg207GeVnngg207GeV WWg189GeVnngg209GeV all numbers in GeV-2 limits @95% CL

  16. W W a0 ac , , an WWg189GeVnngg209GeV WWg207GeVnngg207GeV

  17. Zgg Hadronic events with 2 identified photons Fit to energy spectra and angular distributions Phys.Lett. B540/1-2 (2002) 43

  18. Z Z Z Z a0 ac a0 ac , /L2 NEW limits @95% CL /L2 Opal: nngg, qqgg L3: qqgg

  19. Summary • Triple neutral gauge boson couplings are studied at LEP in Zand ZZ production • Quartic gauge boson couplings are studied at LEP looking forWW,Zand events • No significant anomaly found • Wait for • final LEP results • new Tevatron data • LHC • Linear collider • …..

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