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The tau Lepton

The tau Lepton

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The tau Lepton

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  1. The tau Lepton and Flavour Violation Mass Origin and Supersymmetry March 6 -8 2006 Tsukuba Achim Stahl RWTH Aachen University

  2. t-  m- nm nt npe- ne t-decays: Lepton Number Li = Σ # LeptonsGen i – # AntileptonsGen i conserved in the Standard Model today: many examples Wolfgang Pauli

  3. nt nm Neutrino Oscillations neutrino oscillations violate lepton number !

  4. annihilation nm nt Leptonic tau-Decay nt t- nm W- m- t-  m- forbidden: nm nt

  5. neutrino oscillation nm Leptonic tau-Decay nt t- nm W- m- t-  m- forbidden: nm nt but: energy/momentum conservation

  6. neutrino oscillation nm g LFV-Decay possible decay nt t- nm W- m- t-  m- g forbidden: nm nt but: energy/momentum conservation

  7. LFV-Decay possible decays nt t- nm m- W- g/Z m+ m- t-  m- m+ m-

  8. LFV-Decay possible decays nt r0 Z t- nm W- m- t-  m- r0

  9. neutrino oscillation nm g GIM-Mechanism nt t- nm W- m- t-  m- g

  10. Ue1 Ue2 Ue3 Um1 Um2 Um3 Ut1 Ut2 Ut3 ne nm nt n1 n2 n3 = 1 0 0 0 1 0 0 0 1 Ue1 Um1 Ut1 Ue2 Um2 Ut2 Ue3 Um3 Ut3 Ue1 Ue2 Ue3 Um1 Um2 Um3 Ut1 Ut2 Ut3 unitarity condition * * * * * * * * * g = t-  m- g A  SUti Umif(mi2) ≈ 0 A  SUti Umi = ? A  SUti Umi = 0 * * * GIM-Mechanism ni t- Uti W- * Umi m- br ≈ 10-40

  11. The Paper of X.-Y. Pham Is this true ? Euro Phys J C8 (1999) 513, hep-ph/9810484 for discussion see Tord Riemanns home-page http://www-zeuthen.desy.de/~riemann/

  12. Beyond the S.M. new physics breaks GIM

  13. mg mmm SUSY SO(10) NPB649(2003)189 PRD68(2003)033012 10-8 10-10 SUSY HIGGS PLB549(2002)159 PLB566(2003)217 10-10 10-7 mSUGRA EPJC14(2000)319 PRD66(2002)115013 10-7 10-9 non-universal Z´ PLB547(2002)252 10-9 10-8 Heavy Maj. NRPRD66(2002)034008 10-9 10-10 Some theoretical estimates Beyond the S.M. new physics breaks GIM

  14. Experimental Searches

  15. t-  m- nm nt g t-  m- g Experimental Searches Signal: Background: e+e- m+m-g e+e- t+t- _ e+e- q q

  16. LVF @ b-factories currently best limits ! BaBar approaching 109t-pairs t-  m- g Belle 2004: < 3.1 10-7 BaBar 2005: < 6.8 10-8

  17. LVF @ b-factories currently best limits ! BaBar approaching 109t-pairs prel. ’03 final ‘05 t-  m- g • (r/e-tag) 5.2 % 3.8 % • (total) 9.4 % exp. BGD (r/e) 7.8 ev. 2.8 ev. (total) 6.2 ev. limit (10-8) < 200 < 6.8 Belle 2004: < 3.1 10-7 BaBar 2005: < 6.8 10-8 b-factories reaching the limits at x 10-8

  18. LVF @ LHC t sources at the LHC: 1 year running low luminosity p p  W  t nt p p  Z/g  t t p p  B0  t X p p  B±  t X p p  Bs  t X p p  Ds  t X 1.7 108 8.0 108 4.0 1011 3.8 1011 7.9 1011 1.5 1012 plenty of taus ! no chance to see t- m- g

  19. LVF @ LHC  Tryt-  m- m+ m- Simulation with underlying event low luminosity

  20. LVF @ LHC Source: W  t nt Trigger: Single-Muon L1: pT > 14 GeV HLT:pT > 19 GeV Trigger: Di-Muon L1: pT > 3 GeV HLT:pT > 7 GeV Looks okay 1.7 108t per year

  21. LVF @ LHC DS - Source Trigger: Single-Muon L1: pT > 14 GeV HLT:pT > 19 GeV Trigger: Di-Muon L1: pT > 3 GeV HLT:pT > 7 GeV Trigger-Eff. only 1% 1.5 1012t per year

  22. LVF @ LHC Background Problem with DS source DS F m nm 1 % br. F  m m (g) 10-5br. Does anybody know of a generator for this process ?

  23. LVF Z-Decays m+ g/Z nt m- t- nm m- W- t-  m- m+ m-

  24. LVF Z-Decays m- g/Z m+ nt t- nm m- W- m- m+ t- m-

  25. LVF Z-Decays m- g/Z m+ nt nm m- m- m+ m- t+ t+

  26. LVF Z-Decays p g/Z p nt nm m- p p  Zm- t+ t+

  27. LVF Z-Decays m- nm p g/Z W p nt t+ p p  Zm- t+

  28. Summary

  29. Conclusions LFV tau-decays  Interesting search for physics beyond the S.M. (SUSY and others ) b-factories will approach 10-8 Can we improve a few channels at LHC ? Also look for LVF in Z-decays at LHC !