1. Lepton Photon Symposium LP01 Searches for New Particles Gail G. Hanson Indiana University

2. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 2 OUTLINE Standard Model Higgs Search MSSM Higgs Search Non-SM Higgs Searches Searches for Supersymmetry Single Top Quark Production Searches for Leptoquarks Searches for Excited Fermions Technicolor Searches

3. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 3 STANDARD MODEL HIGGS BOSON November 3, 2000, LEP Experiments Committee (LEPC) presentation: 2.9 s.d. incompatibility with background (1 - CL b ) = 0.0042

4. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 4 SM HIGGS SEARCH CHANNELS Production from Higgsstrahlung e + e   H 0 Z 0 : “Four-Jet Channel:” e + e   H 0 Z 0  bbqq “Missing Energy Channel:” e + e   H 0 Z 0  bb “Tau Channel:” e + e   H 0 Z 0     qq and qq     “Lepton Channel:” e + e   H 0 Z 0  bbe + e  and bb    

5. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 5 HIGGS CANDIDATE?

6. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 6 STATISTICAL PROCEDURE Likelihood ratio Q(m H ) = Each event is assigned a probability density s i of being a signal at Higgs mass m H and a probability b i of being background. Each event is then assigned a weight w i = (s i + b i )/ b i The likelihood of the sample L is the product of the weights. The logarithm is taken, and then the method is log-likelihood ratio. Two hypotheses: Background only (CL b ) Signal + background (CL s = CL s+b /CL b )

7. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 7 EVENT WEIGHTS AT 115 GeV Exp.Channel Rec. m H (GeV) Nov. 3 s/bCurrent s/b 1ALEPH4-jet 1144.7 2ALEPH4-jet 1132.3 3ALEPH4-jet 1100.9 4L3E-miss 1152.10.7 5OPAL*4-jet 1110.40.7 6DELPHI4-jet 1140.50.6 7ALEPHLept 1180.6 8ALEPHTau 1150.5 9ALEPH4-jet 1140.40.5 10OPAL4-jet 1130.5

8. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 8 CURRENT COMBINED RESULTS All four experiments published in 2000. L3 has also published final analysis. New combination: Maximum likelihood ratio at m H = 115.6 GeV. Probability of background fluctuation 2.1 s.d.

9. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 9 1 - CL b = 3.4% CL s+b = 44% m H > 114.1 GeV, 95% C.L. (115.4 GeV expected)

10. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 10 RECONSTRUCTED HIGGS MASS Purity of selection: LooseMediumTight

11. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 11 MSSM HIGGS

12. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 12 SUPERSYMMETRY PARAMETERS

13. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 13 MSSM HIGGS SEARCHES Combined LEP Experiments: m h 0 > 91.0 GeV, m A 0 > 91.9 GeV, 95% C.L. 0.5 < tan  < 2.4 excluded m h -max, m t <174.3GeV

14. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 14 2HDM(II):  = Higgs mixing angle 1  m h 0  58 GeV and 10  m A 0  65 GeV excluded at 95% C.L. for all , tan  m h > 112.9 GeV ADLO comb. Flavour Independent h   m h > 108.2 GeV ADLO comb. HIGGS SEARCHES IN EXTENDED MODELS

15. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 15 SEARCHES FOR SUPERSYMMETRIC PARTICLES Gravity mediated supersymmetry breaking: R-parity: R-parity conservation: SUSY particles are produced in pairs The lightest SUSY particle (LSP) is stable R-parity violating supersymmetry decays Gauge mediated supersymmetry breaking:

16. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 16 SUSY MAP no

17. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 17 SEARCHES FOR SLEPTONS

18. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 18 STOP AND SBOTTOM Limit for  M > 10 GeV  0o0o 97 GeV 56 o 95 GeV Limit for  M > 10 GeV  0o0o 100 GeV 68 o 92 GeV

19. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 19 SQUARKS AND GLUINOS

20. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 20 CHARGINOS   m   > 103.5 GeV for m > 300 GeV

21. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 21 LIMIT ON THE LSP MASS ~ M  0 > 45.6 GeV M  0 > 54 GeV M  0 > 60 GeV

22. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 22 R-PARITY VIOLATION ±

23. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 23 SINGLE TOP QUARK PRODUCTION H1 events with isolated leptons with large missing p T Flavor Changing Neutral Currents (FCNC) CDF searched for ISR and QCD corrections for LEP combination. FCNC suppressed at tree level in SM (GIM mechanism). Small contributions at one- loop level. In e + e   SM ~ 10  9 fb. Extended models, e.g. SUSY and multi-Higgs, can allow FCNC at tree level.

24. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 24 EVENTS WITH ISOLATED LEPTONS AND LARGE MISSING p T Primary Standard Model process is single W production H1 electron muon obs. exp.obs. exp. P T X <25 GeV 6 6.6 2 1.0 P T X >25 GeV 4 1.3 6 1.5 ZEUS electron muon obs. exp.obs. exp. P T X >25 GeV 1 1.1 1 1.3

25. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 25 LEPTOQUARKS Leptoquarks carry baryon and lepton number. Scalar or vector. F = L + 3B is preserved

26. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 26 EXCITED FERMIONS

27. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 27 TECHNICOLOR m  T > 89.1 (79.8) GeV for N D = 9 (2) m  T > 77 (62) GeV for N D = 9 (2)

28. Lepton Photon Symposium LP01 23-28 July 2001Gail G. Hanson 28 SUMMARY AND CONCLUSIONS Is there a light Higgs boson? Will have to wait until ~ 2007 to find out m H > 114.1 GeV, 95% C.L., from direct search. “Hint” of 2 s.d. signal at m H = 115.6 GeV Is there another mechanism for electroweak symmetry breaking? Will we find supersymmetry? Technicolor? Still only questions!…..