Four years after LEP: What have we learned about W-bosons?

Transcription

1 Four years after LEP: What have we learned about W-bosons? Wolfgang Menges Queen Mary, University of London SCIPP Seminar, 8. November 24 Large Electron-Positron Collider W-pair Production Cross Section, Gauge Couplings and Mass Prospects at the International Linear Collider Summary Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 1/4

2 The LEP Collider ALEPH DELPHI L3 OPAL Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 2/4

3 The LEP Collider ALEPH LAKE GENEVA POINT 8. GENEVA CERN POINT 2. CERN Prévessin DELPHI POINT 6. POINT 4. DELPHI L3 - e Electron + e Positron SPS L3 OPAL ALEPH LEP R. Lewi jan. 199 s OPAL Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 2/4

4 The LEP Collider LEP1: s 91 GeV LEP2: s = GeV Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 3/4

5 The LEP Collider LEP1: s 91 GeV LEP2: s = GeV L = 7 pb 1 /exp. Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 3/4

6 The Four Detectors at LEP Forward Chamber A Forward RICH Forward Chamber B Forward EM Calorimeter Forward Hadron Calorimeter Forward Hodoscope Forward Muon Chambers Surround Muon Chambers Barrel Muon Chambers Barrel Hadron Calorimeter Scintillators Superconducting Coil High Density Projection Chamber Outer Detector Barrel RICH Small Angle Tile Calorimeter Quadrupole Very Small Angle Tagger Beam Pipe Vertex Detector Magnet Yoke L3 Hadron calorimeters and return yoke DELPHI Electromagnetic calorimeters Inner Detector Time Projection Chamber Muon detectors Magnet Pole Magnet Coil Muon Chambers e - HadronCalorimeter VertexChamber BGO Support Tube LuminosityMonitor e + Jet chamber Vertex chamber Microvertex detector z θ y ϕ x Presampler Solenoid and pressure vessel Forward detector Silicon tungsten Time of flight detector Wolfgang Menges luminometer Four years after LEP: What have we learned about W-bosons? Page 4/4 Z chambers

7 The OPAL Detector Hadron calorimeters and return yoke Electromagnetic calorimeters Muon detectors Typical symmetric high-energy detector at the symmetric e + e collider LEP Jet chamber Vertex chamber Microvertex detector Good momentum and energy measurement of isolated leptons jets y reconstruct Z and W bosons z θ ϕ x Forward detector Presampler Silicon tungsten luminometer Time of flight detector Solenoid and pressure vessel Z chambers precise tracking system magnetic field good calorimeter system Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 5/4

8 Physics Program of LEP Physics Goals Cross-section (pb) Z e + e hadrons Electroweak Physics: Z bosons W pairs Z pairs gauge couplings CESR DORIS PEP KEKB SLACB PETRA TRISTAN SLC LEP I W - LEP II Centre-of-mass energy (GeV) New Physics: Higgs boson Supersymmetry Technicolor Exotics Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 6/4

9 Self-Couplings in the Standard Model field strength tensor F a µν = µa a ν νa a µ + gf abc A b µ Ac ν Abelian group U(1) Y B µν = µ B ν ν B µ non-abelian group SU(2) L W a µν = µw a ν νw a µ + gɛabc W b µ W c ν Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 7/4

10 Self-Couplings in the Standard Model field strength tensor F a µν = µa a ν νa a µ + gf abc A b µ Ac ν Abelian group U(1) Y non-abelian group SU(2) L B µν = µ B ν ν B µ L 3 = g 2 ( ) µ W a ν νw a µ ɛ abc W bµ W cν W a µν = µw a ν νw a µ + gɛabc W b µ W c ν = ig sin θ w (Ŵ µν µ Ŵ + µν W µ ) A ν + ig sin θ w  µν W µ ν +ig cos θ w (Ŵ µν µ Ŵ + µν W µ ) Z ν + ig cos θ w Ẑ µν W µ ν Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 7/4

11 Self-Couplings in the Standard Model field strength tensor F a µν = µa a ν νa a µ + gf abc A b µ Ac ν Abelian group U(1) Y non-abelian group SU(2) L B µν = µ B ν ν B µ L 3 = g 2 ( ) µ W a ν νw a µ ɛ abc W bµ W cν W a µν = µw a ν νw a µ + gɛabc W b µ W c ν = ig sin θ w (Ŵ µν µ Ŵ + µν W µ ) A ν + ig sin θ w  µν W µ ν +ig cos θ w (Ŵ µν µ Ŵ + µν W µ ) Z ν + ig cos θ w Ẑ µν W µ ν Triple Gauge Boson Couplings γ e W Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 7/4

12 Self-Couplings in the Standard Model field strength tensor F a µν = µa a ν νa a µ + gf abc A b µ Ac ν Abelian group U(1) Y non-abelian group SU(2) L B µν = µ B ν ν B µ L 3 = g 2 ( ) µ W a ν νw a µ ɛ abc W bµ W cν W a µν = µw a ν νw a µ + gɛabc W b µ W c ν = ig sin θ w (Ŵ µν µ Ŵ + µν W µ ) A ν + ig sin θ w  µν W µ ν +ig cos θ w (Ŵ µν µ Ŵ + µν W µ ) Z ν + ig cos θ w Ẑ µν W µ ν Triple Gauge Boson Couplings γ e W Z W e/ tan θ w Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 7/4

13 W Production and Decay e + f 1 e + f 1 e + f 1 γ W f2 f 3 Z W f2 f 3 ν W f2 f 3 e f4 e f4 e f4 Two of three diagrams involve Triple Gauge Couplings W l ν l l ν l BR = 1.6 % 6 decay modes W qql ν l BR = 43.8 % 3 decay modes W qqqq BR = 45.6 % 1 decay mode Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 8/4

14 Theoretical Predictions for W-Pair Production σ WW (pb) 2 LEP PRELIMINARY YFSWW and RacoonWW 2/8/24 Theoretical Challenge not only dominant diagrams all possible four-fermion diagrams 1 18 single W production Z-pair production 17 Z production s (GeV) KoralW & YFSWW: S. Jadach, W. Placzek, M. Skrzypek, B.F.L. Ward, Z. Was RacoonWW: A. Denner, S. Dittmaier, M. Roth, D. Wackerroth Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 9/4

15 Theoretical Predictions for W-Pair Production e + e eν e u d Theoretical Challenge E1 A N1 E1 A N1 E1 A u u D A u u E1 A d D u not only dominant diagrams D D N1 D N1 diagr.1 A d u D diagr.2 A u N1 diagr.3 A D E1 diagr.4 n1 N1 D diagr.5 n1 N1 all possible four-fermion diagrams single W production E1 diagr.6 u N1 E1 diagr.7 D u E1 diagr.8 u N1 E1 diagr.9 u N1 E1 diagr.1 D u Z-pair production E1 Z N1 E1 Z N1 E1 Z n1 N1 Z N1 E1 Z u u D Z production D D D E1 n1 D N1 diagr.11 u diagr.12 u diagr.13 u diagr.14 u diagr.15 D N1 Z Z Z u u E1 d u d D Z Z D D N1 u E1 D u E1 E1 diagr.16 N1 diagr.17 E1 diagr.18 N1 diagr.19 u diagr.2 N1 Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 9/4

16 Theoretical Predictions for W-Pair Production σ WW (pb) 2 LEP PRELIMINARY YFSWW and RacoonWW 2/8/24 Theoretical Challenge not only dominant diagrams all possible four-fermion diagrams 1 18 single W production Z-pair production 17 Z production s (GeV) radiative corrections initial state radiation (ISR) final state radiation (FSR) intermediate state radiation (WSR) KoralW & YFSWW: S. Jadach, W. Placzek, M. Skrzypek, B.F.L. Ward, Z. Was RacoonWW: A. Denner, S. Dittmaier, M. Roth, D. Wackerroth Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 9/4

17 Theoretical Predictions for W-Pair Production Measured σ WW / Gentle 2/8/24 Theoretical Challenge ± ± ± ± ± ± ± ± ±.9 not only dominant diagrams all possible four-fermion diagrams single W production Z-pair production Z production radiative corrections initial state radiation (ISR) final state radiation (FSR) intermediate state radiation (WSR) Gentle/4fan: D. Bardin, J. Biebel, D. Lehner, A. Leike, A. Olchevski, T. Riemann Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 9/4

18 Leptonically Decaying W-Pairs Topology two isolated leptons missing momentum and energy very low background 2 photon events efficiency: ɛ 6 8% purity: p 9% leptonic W-Pair candidate (DELPHI, s = 161 GeV) Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 1/4

19 Semileptonically Decaying W-Pairs Run # Event # 2184 Total Energy : 159. GeV Topology One lepton, two jets missing momentum and energy low background radiative 2 fermion: Z(γ) 4 fermion: Weν e, ZZ, Ze + e y z x golden channel Transverse Imbalance :.242 Longitudinal Imbalance : Thrust :.8569 Major :.4375 Minor :.1295 Event DAQ Time : semileptonic W-Pair candidate (L3, s = 26 GeV) efficiency: ɛ 7 85% purity: p 9% Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 11/4

20 Selection of Semileptonically Decaying W-Pairs OPAL s = 189 GeV E e / GeV log 1 Pr e I 2 / GeV cosθ mis R vis Σp T / GeV loose preselection: visible energy number of tracks identified electron purity 28% cosθ s / GeV Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 12/4

21 Selection of Semileptonically Decaying W-Pairs OPAL s = 189 GeV E e / GeV log 1 Pr e I 2 / GeV cosθ mis R vis Σp T / GeV loose preselection: visible energy number of tracks identified electron purity 28% likelihood selection: electron candidate event properties topology efficiency 86% for L > cosθ s / GeV Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 12/4

22 Selection of Semileptonically Decaying W-Pairs OPAL s = 189 GeV E e / GeV I 2 / GeV log 1 Pr(e) R VIS cosθ mis Σp T / GeV cosθ s / GeV loose preselection: visible energy number of tracks identified electron purity 28% likelihood selection: electron candidate event properties topology efficiency 86% for L >.5 four-fermion and τ rejection: Weν e ZZ Ze + e efficiency 84% Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 12/4

23 Selection of Semileptonically Decaying W-Pairs OPAL s = 189 GeV E e / GeV I 2 / GeV log 1 Pr e R vis loose preselection: visible energy number of tracks identified electron purity 28% likelihood selection: electron candidate event properties topology efficiency 86% for L > cosθ mis Σp T / GeV four-fermion and τ rejection: cosθ s / GeV Weν e ZZ Ze + e efficiency 84% Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 12/4

24 Hadronically Decaying W-Pairs Run : even t 136 : 3472 Ebeam V t x (. 3,. 4,. 88 ) C t r k ( N= 54 Sump= ) Eca l ( N= Hca l ( N= SumE= ) SumE = ) Muon ( N= 3 ) Topology four jets no missing momentum and energy background 4 fermion: ZZ qqqq 2 fermion + QCD: Z qqqq/qqgg Z Y X OPAL, hadronic W-Pair candidate ( s = 25 GeV) efficiency: ɛ 8 9% purity: p 8% Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 13/4

25 Selection of Hadronically Decaying W-Pairs Selection signal e + e W background e + e Z/γ qq Events OPAL s = 189 GeV Events likelihood function log 1 (W CC3 ) log 1 (W 42 ) log 1 (y 45 ) sphericity likelihood cut: L >.24 efficiency 85% background 2% } W production Z qqqq/qqgg } jet topology 5835 events GeV Events Events log 1 (W 42 ) log 1 (W CC3 ) Events Sphericity log 1 (y 45 ) Likelihood Output Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 14/4

26 Cross Section Measurements σ WW (pb) 2 LEP PRELIMINARY YFSWW and RacoonWW 2/8/24 Measured σ WW / RacoonWW 2/8/ ± ± ± ± ± ± ± ± s (GeV) ±.9 error dominated by statistics hadronization modelling is dominant systematic error (.6%) theoretical uncertainty is.5% Aleph, Delphi and L3 results are final OPAL results are exected early next year Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 15/4

27 Leptonic Branching Ratio Measurements Summer 24 - LEP Preliminary W Leptonic Branching Ratios 2/8/24 ALEPH 1.81 ±.29 DELPHI 1.55 ±.34 L ±.32 OPAL 1.4 ±.35 LEP W eν 1.66 ±.17 ALEPH 1.91 ±.26 DELPHI 1.65 ±.27 L3 1.3 ±.31 OPAL 1.61 ±.35 LEP W µν 1.6 ±.15 ALEPH ±.38 DELPHI ±.43 L ±.45 OPAL ±.48 LEP W τν ±.22 χ 2 /ndf = 6.8 / 9 LEP W lν 1.84 ± Br(W lν) [%] χ 2 /ndf = 15 / 11 use cross-section measurement: σ l νl l ν l = 9Br(W l ν l )Br(W l ν l )σ WW σ qql νl = 2Br(W l ν l )Br(W qq)σ WW σ qqqq = Br(W qq)br(w qq)σ WW lepton universality test: Br(W τ ν τ ) Br(W l ν l ) 2.4σ compatibility test: Br(W τ ν τ ) Br(W eν e /µν µ ) 3σ Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 16/4

28 Hadronic Branching Ratio Measurements Summer 24 - LEP Preliminary W Hadronic Branching Ratio CKM interpretation: 2/8/24 ALEPH ±.4 DELPHI ±.48 L ±.52 OPAL ±.61 Br(W qq) 1 Br(W qq) = ( 1 + α s ( ) M 2 W π V CKM ij ) 2 LEP ±.28 χ 2 /ndf = 15 / V cb =.976 ±.14 Br(W hadrons) [%] Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 17/4

29 Triple Gauge Coupplings σ WW (pb) 3 2 LEP PRELIMINARY 2/8/24 total cross section has sensitivity differential distributions have higher sensitivity 1 YFSWW/RacoonWW no ZWW vertex (Gentle) only ν e exchange (Gentle) s (GeV) 5 angles: Production angle cos θ W Decay angles cos θ 1,2, φ 1,2 but not all accessible W-pair topology: f u f d x z * Θ2 ϕ2 * e+ + W y Θ W x ϕ1 * W y e f d * Θ1 f u z Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 18/4

30 Generalization of the Self-Couplings Most general description of the vertex by an effective Lagrangian: (require only Lorentz invariance) L WWV g WWV = V = Z, γ ) ig1 (Ŵ V V µ µν ν Ŵ µν + W ν +iκ V Wµ W ν + ˆV µν +i λ V MW [ ] 2 + g5 V εµνρσ ( ρ Wµ )W ν + W µ ( ρ W ν + ) V σ g4 V W µ W ν + ( µ V ν + ν V µ ) [ ] + i κv 2 W µ W ν + εµνρσ ˆV ρσ + λ V Ŵ 2MW 2 ρµŵ ν +µ ε νραβ ˆV αβ modify SM coupling strength introduce non-sm couplings SM: g V 1 = κ V = 1, all others zero } anomalous couplings ˆV µν Ŵ µ +ρ Ŵρν SM like extensions: g Z 1, κ γ, λ γ (CP, U(1) Q, SU(2) L U(1) Y ) Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 19/4

31 W-pair Reconstruction leptonic decay modes: energy and momentum conservation (4C) mass constraint for l ν l system (2C) use jet charge to distinguish between and W : semileptonic decay modes: energy and momentum conservation (4C) Q W = mass constraint for l ν l and qq system (1/2C) use kinematic fit to improve resolution N W i=1 / Ntot q i p,i.5 i=1 p,i.5 hadronic decay mode: energy and momentum conservation (4C) mass constraint for l ν l and qq system (1/2C) use kinematic fit to improve resolution (u d) (ūd) 1, 1 2 (uū) ( dd), (ud) ( d d) 1 3, pairing efficiency 8% charge efficiency 77% Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 2/4

32 Angular Distributions Entries/bin E CM = 2 GeV quark distribution cos θ W Events/bin W qqqq (OPAL) data SM (λ = ) λ = +.5 λ =.5 Can not tell q u from q d ambiguities! Entries/bin 3 2 quark distribution (folded) cos θ W wrong charge wrong pairing background Entries/bin cos θ * quark distribution (folded) Entries/bin Entries/bin φ j > : φ j < : cos φ * θ 1 j, φ j -cos θ j, φ j + π cos θ jet * φ jet * Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 21/4

33 Optimal Observables Transform the 5 angles into 1 variable with maximal sensitivity The differential cross-section can be expanded in terms of the anomalous couplings α: dσ(ω, α) dω = S () (Ω) + i α i S (1) i (Ω) + i,j α i α j S (2) ij (Ω), with Ω = (cos θ W, cos θ 1, φ 1, cos θ 2, φ 2 ) and α = (gz 1, κ γ, λ) or g Z 5. Define Optimal Observables as O (1) i = S(1) i O (2) S () ij = S(2) ij S () Events/bin O (1) λ Aleph, Delphi and Opal use OO s L3 use a likelihood fit Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 22/4

34 OPAL Combination 1-Parameter Fits log L 3 2 log L 3 2 OPAL: 1 1 W qqqq W qql ν l W l ν l l ν l log L κ γ z g 1 qqqq qqlν lνlν W event rate λ event rate (only GeV) combined Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 23/4

35 LEP Combination 1-Parameter Results Combine the data from all four experiments using the likelihood functions and include correlation of systematics: κ γ = g1 Z = λ = Correlated systematics κ γ g Z λ O(α) corrections σ WW predictions Fragmentation & Hadronisation Bose-Einstein Correlation Colour Reconnection σ Weνe predictions Aleph: still preliminary Delphi: still preliminary L3: all numbers final OPAL: WW numbers final quadratic sum dominat source is O(α) corrections measurement is dominated by statistical error Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 24/4

36 LEP Combination 2-Parameter Contours γ λ.2 γ κ.2 Experiments:.1.1 e + ALEPH DELPHI L3 OPAL Processes: e + e W e + e Weν e e + e γν ν ν e e + ν e γ κ g Z Z 1 g1 LEP Preliminary 95% C.L. 68% C.L. γ, Z f f W γ.1 2d fit result e e e ν e LEP charged TGC Combination 23 λ γ Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 25/4

37 LEP Combination 2-Parameter Contours Z 1 Experiments: λ g ALEPH DELPHI L3 OPAL Processes: κ γ κ γ e + e W e + e Weν e e + e γν ν λ D Fit 95% C.L. OPAL (qqqq) e + e γ, Z ν e f f e e + e W γ ν e ν e SM g Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 25/4 Z 1

38 LEP Combination 2-Parameter Contours Z 1 Experiments: λ g ALEPH DELPHI L3 OPAL Processes: κ γ κ γ e + e γ, Z e + e W e + e Weν e e + e γν ν ν e f f e e + e W γ ν e ν e λ D Fit 95% C.L. OPAL (qqqq) 2D Fit 95% C.L. OPAL (all) SM g Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 25/4 Z 1

39 LEP Combination 2-Parameter Contours Z 1 Experiments: λ g ALEPH DELPHI L3 OPAL Processes: κ γ κ γ e + e γ, Z e + e W e + e Weν e e + e γν ν ν e f f e e + e W γ ν e ν e λ D Fit 95% C.L. OPAL (qqqq) 2D Fit 95% C.L. OPAL (all) 2D Fit 95% C.L. LEP (all) SM g Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 25/4 Z 1

40 use only semileptonic and hadronic channel (not much information in leptonic channel) apply kinematic fit with constraints to improve resolution W-boson Mass reconstruct ν in semileptonic channel improve resolution: 7 GeV 3 GeV decrease detector systematics essential for jet-pairing in hadronic channel ALEPH: jet pairing selection DELPH: use all combinations L3: highest 5C fit probability OPAL: jet pairing selection mass extraction method: direct fit of Breit-Wigner function not possible reweight MC to data (Aleph, L3, Opal) likelihood convolution (Delphi) Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 26/4

41 W-boson Mass Spectra Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 27/4

42 LEP Combination Winter 23 - LEP Preliminary Winter 23 - LEP Preliminary ALEPH [1996-2] 8.375±.62 ALEPH [1996-2] 8.431±.117 DELPHI [1996-2] ±.89 DELPHI [1996-2] 8.374±.119 L3 [1996-2] 8.314±.87 L3 [1996-2] 8.485±.127 OPAL [ ] 8.516±.73 OPAL [ ] 8.47±.12 LEP 8.411±.44 LEP 8.42±.17 LEP working group correl. with 4q =.18 LEP working group correl. with non-4q = M W [GeV] (non-4q) M W [GeV] (4q) LEP combined (preliminary) M W = ±.42/GeV M W (qqqq qql ν l ) = +22 ± 43 MeV Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 28/4

43 LEP Systematic Uncertainties LEP combined: M W = ±.42 GeV LEP combined: M W = ±.29(stat.) ±.31(syst.) GeV systematic uncertainties in MeV source qql ν l qqqq Combined ISR/FSR Detector Systematics LEP Beam Energy Hadronisation Colour Reconnection Bose-Einstein Correlations Other Total Systematics Statistical Total Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 29/4

44 Hadronisation e + e γ γ, Z W W q q l ν l H a d r o n i z a t i o n different fragmentation & hadronisation models exist Jetset Herwig Ariadne hadronisation models tuned to describe Z data, but tunes are different different models give W mass shifts between 1 5 MeV some differences due to kaon and baryon rates Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 3/4

45 Colour Reconnection colour exchange between decay products of the two W-bosons several phenomenological models exist Sjöstrand-Khoze I and II Ariadne Herwig-CR Rathsman LEPWW/MASS/23-1 is there Colour-Reconnection? what is the effect on the W mass? use MC models use data Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 31/4

46 Bose-Einstein Correlation production of pairs of low momentum particles (π π, π + π + and π π ) is enhanced Bose-Einstein Correlation is a well known effect only phenomenological models are available is there Bose-Einstein Correlation between particles from differen W- bosons? use MC models use data ρ(± ±) [GeV -1 ] ρ(+ ) [GeV -1 ] (a) Eur. Phys. J. C35 (24) data full BEC OPAL 6 intra BEC 4 no BEC Q [GeV] 8 (b) data full BEC intra BEC OPAL 6 no BEC Q [GeV] Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 32/4

47 Bose-Einstein Correlation production of pairs of low momentum particles (π π, π + π + and π π ) is enhanced Bose-Einstein Correlation is a well known effect only phenomenological models are available LEPWW/FSI/22-2 PRELIMINARY inter-w BEC ALEPH R * DELPHI D -.23±.41.57±.22 is there Bose-Einstein Correlation between particles from differen W- bosons? use MC models use data L3 D.8±.21 L3 ρ.2±.26 (corr L3.95) χ 2 /dof = 4.1/3 LEP.24± fraction of model seen Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 32/4

48 World Average and Interpretation W-Boson Mass [GeV] TEVATRON ±.59 LEP ± LEP1, SLD Data LEP2, pp Data 68% CL Average ± m W [GeV] χ 2 /DoF:.3 / 1 NuTeV ±.84 LEP1/SLD ±.32 LEP1/SLD/m t ±.23 M W = 8.425±.34 GeV m W [GeV] α m H [GeV] Preliminary m t [GeV] direct and indirect measurements consistent within SM Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 33/4

49 The International Linear Collider e + damping ring linear accelerator base design s =.5 1TeV positron preaccelerator ositron collision ysics experiments positron source ux. positron and electron source e - x-ray laser 33 km L = 5fb 1 e (and e + ) polarisation damping ring linear accelerator e - high precision detector(s) electron sources (HEP and x-ray laser) Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 34/4

50 Triple Gauge Couplings focus on the golden channel : all three decay modes: qqeν e qqµν µ qqτ ν τ s = 5 GeV, L = 5 fb 1 process σ[pb] ɛ[%] N B[%] WW qql ν l WW qqqq WW l ν l l ν l qq ZZ Ze + e Weν background GeV 8 GeV 5 fb 1 1 fb 1 g1 Z κ γ λ γ all errors in [ 1 4 ] 5 GeV 8 GeV 5 fb 1 1 fb 1 g Z g Z κ Z λ Z CP conserving couplings: 1 4 C or P violating couplings: 1 3 higher energy: factor 2 in sensitivity Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 35/4

51 Longitudinal Beam Polarization γ Z ν γ Z left-handed electrons right-handed electrons σ at 5 GeV 1% 8% P e P e + 1% 6% L R L R R L.2.8 σ = 1 4 (1 P e +)(1+P e )σ R+ 1 4 (1+P e +)(1 P e )σ L polarized electrons and positrons help to switch off the t-channel ν-exchange disentangle WWZ and WWγ couplings Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 36/4

52 Results with Beam Polarization The simultaneous use of data with opposite beam polarisations (±P e ) is needed to separate WWγ and WWZ couplings. 8 GeV, no polarization 1d [ 1 4 ] 5d [ 1 4 ] g Z 1 κ γ λ γ κ Z λ Z g Z κ γ λ γ κ Z λ Z GeV, e polarization (R+L) 1d [ 1 4 ] 5d [ 1 4 ] g Z 1 κ γ λ γ κ Z λ Z g Z κ γ λ γ κ Z λ Z Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 37/4

53 Comparison with other Measurements/Studies κ γ λ γ κγ λγ LEP TEV LHC TESLA 5 TESLA 8 TESLA 5 γγ TESLA 5 eγ LEP TEV LHC TESLA 5 TESLA 8 TESLA 5 γγ TESLA 5 eγ Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 38/4

54 W-Mass Measurement at ILC return to the W-threshold and perform a high presicion threshold scan with ploarised beams Event ratio e e + σ W W σ bkgd 1 R L (1 + P )(1 + P + ) (1 + P P + ) 2 L R (1 P )(1 P + ) (1 + P P + ) L 1 + P 1 5 R 1 + P R 1 P 1 7 L 1 P % of luminosity in RL mode 12% of luminosity in LR mode 16% of luminosity in other modes fb 1 M W = 6 MeV (1 year) s (GeV) Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 39/4

55 many aspects of W-bosons have been studied at LEP the properties of the W-boson are consistent with the SM Summary the precise measurement of the W-boson mass can be used to constrain the Higgs mass Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 4/4

56 many aspects of W-bosons have been studied at LEP the properties of the W-boson are consistent with the SM Summary the precise measurement of the W-boson mass can be used to constrain the Higgs mass Z 1 a high luminosity linear collider will give even more precise measuements g.4.2 2D Fit 95% C.L. OPAL (qqqq) 2D Fit 95% C.L. OPAL (all) 2D Fit 95% C.L. LEP (all) Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 4/4 κ γ

57 many aspects of W-bosons have been studied at LEP the properties of the W-boson are consistent with the SM Summary the precise measurement of the W-boson mass can be used to constrain the Higgs mass Z 1 a high luminosity linear collider will give even more precise measuements g.4.2 2D Fit 95% C.L. OPAL (qqqq) 2D Fit 95% C.L. OPAL (all) 2D Fit 95% C.L. LEP (all) 5D Fit 95% C.L. TESLA (5 GeV) Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 4/4 κ γ

58 Radiative Corrections e + e e + γ W W f 1 f2 f 3 f4 e + e W W γ f 1 f2 f 3 f4 e + e γ W W ISR FSR WSR f 1 e + f 1 e + W f 1 f2 f 3 f4 f 1 photon radiation in initial state (ISR) final state (FSR) intermediate state (WSR) Coulomb-corrections e W W γ W f2 W f 3 f4 e W γ f2 W type (mf ) type (ff ) type (if) f 3 f4 e W γ f2 f 3 f4 full O(α) corrections not feasible e + e W W W γ W f 1 f2 f 3 f4 e + e γ W W W f 1 f2 f 3 f4 e + e W W W γ type (mm ) type (im) type (mf) f 1 f2 f 3 f4 full O(α) corrections for dominant contributions KoralW & YFSWW RacoonWW Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 41/4

59 Preselection Preselection not as W l ν l l ν l or W qql ν l selected E vis >.7 s M inv >.75 s E max <.3 s N jet > 1 Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 42/4

60 Optimal Observables Events/bin Events/bin Events/bin O (1) κ γ O (2) κ γ.5 1 O (2) κ γ, g 1 Z Events/bin Events/bin Events/bin O (1) g 1 Z O (2) κ γ, λ O (2) g 1 Z Events/bin Events/bin Events/bin O (1) λ -1 O (2) λ 1 2 O (2) g 1 Z, λ 2 4 Coupling paramters: κ γ, g Z 1, λ Optimal Observables: 1. order 2. order mixed terms E CM > 18 GeV SM (λ = ) λ = +.5 data λ =.5 background Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 43/4

61 Results 1-Parameter Measurement only statistical errors inclusive systematic errors κ γ = g Z 1 = λ = g Z 5 = κ γ = g Z 1 = λ = g Z 5 = only statistical errors 3-Parameter Measurement inclusive systematic errors κ γ = g Z 1 = λ = κ γ = g Z 1 = λ = Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 44/4

62 LEp TGC Results Experiments κ γ g Z 1 λ ALEPH DELPHI L OPAL Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 45/4

63 Strong Electroweak Symmetry Breaking No light Higgs particle? Unitarity requires that the interaction among gauge bosons become strong! (symmetry breaking scale Λ O(TeV)) Strong Electroweak Symmetry Breaking effective Lagrangian for weak gauge bosons L 1 = α 1(g1 Z, κ γ, κ Z ) gg 16π 2 2 B µν tr (σ 3 W µν) L 2 = α 2(g1 Z, κ γ, κ Z ) ig B 16π 2 µν tr L 3 = α 3(g1 Z, κ γ, κ Z ) 2ig tr 16π 2 (σ 3 V µ V ν) (W µν V µ V ν) α i s are related to energy scale of new physics: α i 16π 2 = ( limit on scale Λ i ) GeV Λ i Problems transformation is singular (only two α s) without polarization κ γ and κ Z are strongly correlated Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 46/4

64 Strong Electroweak Symmetry Breaking take α 2 and α 3 from measurement of g Z 1, κ γ, κ Z in addition take α 1 from other measurements (e. g. ɛ 1 from GigaZ) α % C.L. 68% C.L..5.5 α 2 1 Scale of new physics α 3 α 3 s 5 GeV 8 GeV R Ldt 5 fb 1 1 fb P e = %, P e + = % Λ TeV 2.1 TeV α % C.L α 1 α 1 (GigaZ) α 1 = 68% C.L..5.5 α α 3 Λ TeV 3.1 TeV P e = 8%, P e + = 6% Λ TeV 1.3 TeV Λ TeV 14.1 TeV α 1 = Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 47/4

65 Predictions in MSSM Models 1 4 A. Arhib et al, hep-ph/ Sensitivity at TESLA κ γ : ±6 1 4 L = 5 fb 1 s = 5 GeV Wolfgang Menges Four years after LEP: What have we learned about W-bosons? Page 48/4