L i = Σ # Leptons Gen i – # Antileptons Gen i conserved in the Standard Model Wolfgang Pauli n  p e-en  p e-e -  --  -  -decays: today: many examples

  neutrino oscillations violate lepton number !

-- --   W-W-  -   -    annihilation forbidden:   

-- --   W-W-  -   - forbidden:    neutrino oscillation  but: energy/momentum conservation

-- --   W-W-  -   - forbidden:    neutrino oscillation  but: energy/momentum conservation  

-- --   W-W-  -   -  +  -  Z ++ --

-- --   W-W-  -   -  0 Z 00

-- --   W-W-  -   - neutrino oscillation   

-- -- i W-W-  -   -   UiUi UiUi

Euro Phys J C8 (1999) 513, hep-ph/ for discussion see Tord Riemanns home-page

new physics breaks GIM

 SUSY SO(10) NPB649(2003)189 PRD68(2003) SUSY HIGGS PLB549(2002)159 PLB566(2003) mSUGRA EPJC14(2000)319 PRD66(2002) non-universal Z´ PLB547(2002) Heavy Maj. N R PRD66(2002) Some theoretical estimates

currently best limits ! approaching 10 9  -pairs  -   -  Belle 2004: < BaBar 2005: < BaBar

currently best limits ! approaching 10 9  -pairs  -   -  Belle 2004: < BaBar 2005: < BaBar prel. ’03 final ‘05  (  /e-tag ) 5.2 % 3.8 %  ( total ) 9.4 % exp. BGD (  /e ) 7.8 ev. 2.8 ev. ( total ) 6.2 ev. limit (10 -8 ) < 200 < 6.8 b-factories reaching the limits at x 10 -8

 sources at the LHC: p p  W    p p  Z/    p p  B 0   X p p  B ±   X p p  B s   X p p  D s   X year running low luminosity plenty of taus ! no chance to see  -   - 

  Try  -   -  +  - Simulation with underlying event low luminosity

Source: W    Trigger: Single-Muon L1: p T > 14 GeV HLT: p T > 19 GeV Trigger: Di-Muon L1: p T > 3 GeV HLT: p T > 7 GeV Looks okay   per year

D S - Source Trigger: Single-Muon L1: p T > 14 GeV HLT: p T > 19 GeV Trigger: Di-Muon L1: p T > 3 GeV HLT: p T > 7 GeV Trigger-Eff. only 1%   per year

Background Problem with D S source D S    1 % br.    br. Does anybody know of a generator for this process ?

-- --   W-W-  -   -  +  -  Z ++ --

-- --   W-W-  -  +  -   -  Z ++ --

++ --    -  +   -  +  Z ++ --

++ --   p p  Z   -  +  Z p p

++ --   p p  Z   -  +  Z p p W

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