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

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

Introduction (2) Anomalous Couplings Standard Model – nothing to expect New Physics parameterized with effective Lagrangian enhancing existing couplings introduce non-SM couplings Anomalous Couplings

Neutral Triple Gauge Couplings Standard Model e+ e- e Z Z/g 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

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

e+e-g*  ZZ, e+e- Z*  ZZ Use s, |cos qZ|, Neural Net, Optimal Observ. new since summer 2001 limits @95% CL f4 g f5 g f4 Z f5 Z [-0.17;0.19] [-0.30;0.28] [-0.34;0.38] [-0.36;0.38]

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 h1 g h2 g [-0.06;0.05] [-0.05;0.02] h3 g h4 g [-0.05;0.00] [-0.00;0.04]

g*Zg, Z*Zg Measurements (2) unchanged since summer 2001 limits @95% CL h1 Z h2 Z [-0.17;0.15] [-0.10;0.09] h3 Z h4 Z [-0.23;0.11] [-0.07;0.15]

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

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

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

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

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

Opal fits couplings WWgg & ZZgg e+e- nngg Opal fits couplings WWgg & ZZgg Estimations of a0 /2 , ac /2 obtained looking for anomalous increase Opal prelim. OPAL-PN510

, , a0 W ac W an a0 W /2 ac W /2 an /2 all numbers in GeV-2 Delphi , , an -0.031 GeV-2 < a0/2 < 0.030 GeV-2 -0.069 GeV-2 < ac/2 < 0.070 GeV-2 -0.45 GeV-2 < an/2 < 0.41 GeV-2 Summer 2001 LEP combination a0 W /2 ac W /2 an /2 Delphi [-0.018,0.018] [-0.057,0.030] [-0.16,0.12] L3 [-0.015,0.015] [-0.048,0,026] [-0.14,0,13] Opal [-0.054,0,052] [-0.15,0.14] [-0.61,0.57] WWg 209GeV WWg 207GeV nngg 207GeV WWg 189GeV nngg 209GeV all numbers in GeV-2 limits @95% CL

a0 W ac W , , an WWg 189GeV nngg 209GeV WWg 207GeV nngg 207GeV

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

, a0 Z ac Z /L2 /L2 [-0.009,0.026] [-0.034,0.046] a0 limits @95% CL ac NEW limits @95% CL ac Z /L2 Opal: nngg, qqgg L3: qqgg

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