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

15 november 2004SAC presentation2 LEP construction

15 november 2004SAC presentation3 L3 DELPHIDELPHI

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

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

15 november 2004SAC presentation6 Z line shape Moriond 1990: m Z = ± 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 = ± 2.1 MeV  Z = ± 2.3 MeV N = ± One of the main LEP results

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

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

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 !

15 november 2004SAC presentation10 Top mass: predicted by LEP Prediction m top from EW fit EPS93 Marseille: m top = 166 – GeV ICHEP94 Glasgow: m top = GeV and CDF saw excess due to top at m top = GeV EPS95 Brussels: both CDF and D0 observed top at predicted mass Great success Standard Model (Nobel prizes for ‘t Hooft and Veltman)

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: 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

15 november 2004SAC presentation12  lepton: a puzzle solved  lifetime related to  lifetime,  mass,  mass and leptonic  branching ratio Up to 1992 a  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

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

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 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

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

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

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

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

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

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

15 november 2004SAC presentation : 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

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)

15 november 2004SAC presentation24 ALEPH Higgs candidate

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 > GeV (115.3 expected) Final LEP Higss search results

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

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

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 > 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