1. 15 november 2004SAC presentation1 LEP programme Final report Peter Kluit Thanks to: Wes Metzger, Jan Timmermans and my LEP collegues

2. 15 november 2004SAC presentation2 LEP construction

3. 15 november 2004SAC presentation3 L3 DELPHIDELPHI

4. 15 november 2004SAC presentation4 First study B. Richter 1976 C~43 km, E=2*100 GeV, L=10 32 cm -2 s -1, 8 interaction points Les Houches study 1979 study of Z production and decay study of WW production Higgs search searches for new leptons, quarks 3 and 4 jet structures Start construction 1983: C=27 km NIKHEF joins DELPHI & L3

5. 15 november 2004SAC presentation5  Events/experiment:  4.5 M Z events LEP1  10000 WW events  600 ZZ events  250 single-W events  LEP1 (1989-1995): ~200 pb -1 /exp LEP2 (1996-2000): ~700 pb -1 /exp LEP2

6. 15 november 2004SAC presentation6 Z line shape Moriond 1990: m Z = 91171 ± 12 ± 32 (incl.  E LEP ) MeV  Z = 2538 ± 26 ± 28 MeV N = 3.04 ± 0.12 First evidence 3 generations Now status up to end 2003: m Z = 91187.5 ± 2.1 MeV  Z = 2495.2 ± 2.3 MeV N = 2.9841 ± 0.0083 One of the main LEP results

7. 15 november 2004SAC presentation7 Beam energy precision  0.2 MeV from resonant depolarisation But corrections needed due to: TIDES LEVEL LAKE TGV

8. 15 november 2004SAC presentation8 Vertex Detectors: Precise  -lepton b-quark studies here the DELPHI LEP2 vertex detector

9. 15 november 2004SAC presentation9 R b =  b /  had and top quark mass Summer 1992:  b = 373  9 MeV  I 3 b = -1/2 (370 MeV; for I 3 b =0: 24 MeV)  Top quark must exist Now (end 2003): R b determined with 0.3% R b is also sensitive to top quark mass, but much less than sin 2 q eff !

10. 15 november 2004SAC presentation10 Top mass: predicted by LEP Prediction m top from EW fit EPS93 Marseille: m top = 166 –19 -22 GeV ICHEP94 Glasgow: m top = 178 -11 -19 GeV and CDF saw excess due to top at m top = 174 -10 -23 GeV EPS95 Brussels: both CDF and D0 observed top at predicted mass. +17 +19 +11 +18 +10 +13 Great success Standard Model (Nobel prizes for ‘t Hooft and Veltman)

11. 15 november 2004SAC presentation11 Two most precise sin 2  eff values from SLD A LR and LEP A 0,b differ by 2.9  lept FB SM: 0.1036 A 0,b (and also A 0,c ) prefer a high value for the Higgs boson mass FB A puzzle left ….. : comparison sin 2 q eff lept

12. 15 november 2004SAC presentation12  lepton: a puzzle solved  lifetime related to  lifetime,  mass,  mass and leptonic  branching ratio Up to 1992 a 2-2.3  discrepancy between the coupling constants g  and g  In 1992 a new, more precise  mass by BES Now  -  -e universality tested at few per-mille, thanks to high precision vertex detectors

13. 15 november 2004SAC presentation13 B s oscillations: to be discovered  m s > 14.4 ps -1 at 95% C.L. Continuous improvements in analysis techniques B d oscillations discovered at LEP

14. 15 november 2004SAC presentation14 B physics and CKM matrix Excellent agreement with sin2 b from BaBar/Belle Profound test of SM charged current sector |V td | from B d 0 – B d 0 oscillations |V ts | from B s 0 - B s 0 oscillations |V cb | from semileptonic b  cl transitions |V ub | from semileptonic b  ul transitions

15. 15 november 2004SAC presentation15 QCD: test of gluon selfcoupling From fit to angular distributions in 4-jet events. Rel. strength of couplings qqg, ggg, gqq depends on gauge group through Casimir factors C F, C A, T F T F / C F

16. 15 november 2004SAC presentation16 QCD: running of  s Results from fits to different event shape variables. Combined fit at all energies:  s (M Z ) = 0.1201  0.0003  0.0009  0.0047 (Note this year Nobel Prize) (stat) (exp.syst) (theor.hadr.) (theor.ev. shapes)

17. 15 november 2004SAC presentation17 only exchange No ZWW vertex WW cross section Clear evidence for the SU(2) x U(1) Gauge structure CC03 diagrams: Theory predictions include full O(  em ) corrections; theory error  0.5% Triple Gauge Coupling

18. 15 november 2004SAC presentation18 Single W WW  DLO Quartic Gauge Couplings

19. 15 november 2004SAC presentation19 W mass reconstruction Reconstructed directly from the decay products Constrained fits improve mass resolution from  8 GeV to  3 GeV before 4C fit after 4C fit qqqq qq  qq  qqe

20. 15 november 2004SAC presentation20 W mass: LEP combined results (end 2003) Not yet final Working on systematics, mainly in 4q Apart from NuTeV result ( scattering) Very good agreement between direct and indirect measurements

21. 15 november 2004SAC presentation21 We searched….. and searched….. But sometimes…… No Higgses, 4 th -generation, sleptons, squarks, charginos, neutralinos.... Large part of the MSSM parameter space excluded

22. 15 november 2004SAC presentation22 1995: 130-136 GeV 4-jet events Sum of di-jet masses with smallest  M 16 events (8.3 exptd) Prob. accumulation in 6.3 GeV bin: 0.01% ALEPH Why it is good to have more than one experiment

23. 15 november 2004SAC presentation23 SM Higgs search Higgs strahlung: dominantWW fusion: small (can go beyond ‘kinematical limit’) Final states: (Higgs to bb or  ) bbqq (4-jet channel) bb (missing energy channel) bbee, bb  (leptonic channel) bb ,  bb (tau channel)

24. 15 november 2004SAC presentation24 ALEPH Higgs candidate

25. 15 november 2004SAC presentation25 Small excess around 116 GeV but less than 2  (mainly coming from ALEPH candidates and from four-jet events) Excess was 2.9  on 3/11/2000 CL s = CL s+b / CL b when CL s < 0.05 the hypothesis is rejected at 95% CL Lower limit on Higgs mass M H > 114.4 GeV (115.3 expected) Final LEP Higss search results

26. 15 november 2004SAC presentation26 Results of different fits: using only Z pole data using all data using all data but NuTeV Global electroweak fit

27. 15 november 2004SAC presentation27 Good consistency between direct and indirect measurement of m t and m W Both prefer low Higgs boson mass m H < 219 GeV at 95% CL Light Higgs to be discovered at LHC

28. 15 november 2004SAC presentation28 Conclusions  LEP was great!  Full gauge structure of the SM has been measured, and many measurements in good agreement with the SM prediction  Fantastic precision measurements of W and Z boson, b quark and  lepton properties, including the CKM matrix  SM Higgs boson not yet found: M H > 114.4 GeV  NIKHEF was involved in many important analyses:  total output: ~ 300 journal papers/experiment  PhD theses: 14 DELPHI, 35 L3 (of which 22 KUN)  Papers still to come: ~55 DELPHI and ~20 L3