1. March 22 2007 @ Heidelberg 1 Majorana neutrino spectroscopy and measuring relic neutrino M. Yoshimura hep- ph/0611362 Why atoms ? Another or perhaps a unique way of Majorana detection Measurement of absolute mass scale Possibility of detecting relic neutrino hep-ph/0703019

2. March 22 2007 @ Heidelberg 2 Significance of discovering Majorana neutrino Neutral fermions follow economic Majorana eq or the same Dirac eq as charged ? Leading to lepton number violation and lepto- genesis particle = anti-particle missing partner for leptogenesis Contributing to better understanding of seesaw mechanism and GUT

3. March 22 2007 @ Heidelberg 3 M vs D

4. March 22 2007 @ Heidelberg 4 Merits and demerits of atomic process Infinitely many small energies Small pair emission rate How to enhance is crucial resonance by energy input strong field

5. March 22 2007 @ Heidelberg 5 Majorana ｖｓ Dirac equations: chirally projected solutions

6. March 22 2007 @ Heidelberg 6 Unique signature of Majorana = interference of identical fermions Effective only for pair emission Appear only (ii) threshold; proportional to m_i^2 Can be positive or negative Direct test of Majorana nature cf LV in

7. March 22 2007 @ Heidelberg 7 2 promissing atomic processes Low level metastable atoms laser irradiated Rydberg atoms microwave irradiated (not discussed here)

8. March 22 2007 @ Heidelberg 8 Neutrino pair emission from laser irradiated metastable state

9. March 22 2007 @ Heidelberg 9 Rough estimate of rate

10. March 22 2007 @ Heidelberg 10 Refinement

11. March 22 2007 @ Heidelberg 11

12. March 22 2007 @ Heidelberg 12 Majorana vs Dirac 6 channels available

13. March 22 2007 @ Heidelberg 13 Numerical estimate w.Y. Okabayashi Input angles and masses: case of normal hierarchy

14. March 22 2007 @ Heidelberg 14 Red Blue Mass varied 300(meV) M : ~9% D : ~7% 500(meV) M : ~4% D : ~3% 700(meV) M : ~2% D : ~1% 900(meV) M : ~1% D : ~0.8% Effect

15. March 22 2007 @ Heidelberg 15

16. March 22 2007 @ Heidelberg 16 Large mass effects

17. March 22 2007 @ Heidelberg 17 Red Blue Mixing angle varied 300(meV) M : ~8% D : ~6% 500(meV) M : ~3% D : ~2% 700(meV) M : ~2% D : ~1% 900(meV) M : ~1% D : ~0.8% Finite mass effect

18. March 22 2007 @ Heidelberg 18 Theta_12 effect

19. March 22 2007 @ Heidelberg 19 Case of inverted mass hierarchy ① ①② ③④ ⑤ ⑥ ② ③ ④ ⑤ ⑥

20. March 22 2007 @ Heidelberg 20 Observability of relic neutrino w. T. Takahashi hep-ph/0703019 Pauli blocking effect

21. March 22 2007 @ Heidelberg 21

22. March 22 2007 @ Heidelberg 22 Crucial question how large the “threshold ” region

23. March 22 2007 @ Heidelberg 23 Magnitude of Pauli blocking

24. March 22 2007 @ Heidelberg 24 m_1 dependence for standard 1.9 K For m_1 > 5 meV, the “threshold” region is narrow For m_1 < 1 meV, the “threshold” region is wide

25. March 22 2007 @ Heidelberg 25 Temperature measurement possible ? For m_1 < 1meV, temperature measurement is not difficult

26. March 22 2007 @ Heidelberg 26 12 threshold Smaller effect with a larger rate

27. March 22 2007 @ Heidelberg 27 Early universe probed by relic neutrino Decoupling temperature Early universe after neutrino decoupling and before e^+ annihilation Large lepton asymmetry Constraint on sterile neutrino Surprizes ?

28. March 22 2007 @ Heidelberg 28 Measuring the lepton asymmetry Definitive test of leptogenesis Extremely difficult, (12) threshold most promissing

29. March 22 2007 @ Heidelberg 29 Experiments are not easy: a possible strategy Discovery of atomic pair emission Mass measurement M/D distinction Relic detection

30. March 22 2007 @ Heidelberg 30 Level structure of candidate atom

31. March 22 2007 @ Heidelberg 31 Summary Discussed laser irradiated pair emission to determine the magnitude and the nature of neutrino masses Identical particle effect of Majorana particles Neutrino mass spectroscopy towards 1 meV range Relic neutrino search