CONTENT Standard model does not permit LFV Most common introduction of neutrino masses

1. Lepton flavour violation (tau decays)A.Ilakovac, Dept. of Physics, Faculty of Science, U. of Zagreb, Croatia CONTENT Standard model does not permit LFV Most common introduction of neutrino masses Sources of LFV/LNV Model-independent (operator) analysis of LFV with SM fields LFV mechanisms Connecting LFV with neutrino parameters Examples of interrelations between processes Hadronic part of LFV amplitudes Some results for tau-lepton processes Conclusions

2. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

3. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

4. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

5. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

6. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

7. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

8. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

9. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

10. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

11. Two approaches to determine see-saw parameters: • top-down: start with a specific model (GUT, Froggatt-Nielsen, strings,…) and compare the predictions with the experiments, [many different possibilities] • 2. bottom-up: exploit all the information available at low energies on the leptonic sector in order to resconstruct the high-energy theory; completely phenomenological, [very difficult in practice] • [A. Ibarra: impossible in SMv ; possible in MSSM] A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

12. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

13. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

14. 2. LFV and LFC A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

15. Hadronic part of LFV amplitudes • tau-lepton is heavy enough to decay into hadrons – LFV with hadrons in the final state possible • - simplest hadronization methods: • (a) PCAC –axial vector • (b) VMD –vector • (c) chiral perturbation theory – scalar and • pseudoscalar (e.o.m. for current quark masses • gives similar results) • (d) tensor: e.o.m. for current quark masses and (b) A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

16. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

17. M.J. Herrero, hep-ph/0510405 A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

18. P. Paradisi, Flavour in the era of the LHC, CERN, February 2006 A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

19. CONCLUSIONS 1.Lepton flavour violation must occur at some level. 2. Discovery of any of LFV processes, except neutrino oscillations would give important information on the structure of theory. 3. LFV processes have to be always analyzed taking into account information of all other LFV and LFC processes. 4.Many theoretical models are not completely explored, and in specific regions of parameter space give results comparable to the present experimental limits for BRs of neutrinoless LFV processes. For some SUSY models large regions of parameter space are excluded by LFV experimental data. In this context tau-lepton LFV data play important role. A. Ilakovac, U. of Zagreb, Novosibirsk, February 2006

20. SM parameters m LFV processes MSSM MSSM MR RGE SO(10) structure MD, MR