1. Towards Majorana neutrino spectroscopy M. Yoshimura
Why atoms ?
Another or perhaps a unique way of Majorana detection　
Measurement of absolute mass scale
hep-ph/
Possibility of detecting relic neutrino
hep-ph/

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. M vs D

4. Merits and demerits of atomic process
Infinitely many small energies
Small pair emission rate
How to enhance;
resonance by energy input
strong field

5. Majorana ｖｓ Dirac equations: chirally projected solutions

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. 2 promissing atomic processes
Low level metastable atoms laser irradiated
Rydberg atoms microwave irradiated
(not discussed here)

8. Neutrino pair emission from laser irradiated metastable state

9. Rough estimate of rate

10. Refinement

11. Threshold behavior
6 channels

12. Numerical estimate w.Y. Okabayashi
Input angles and masses

14. Total rate / rate for massless
Several % mass effects for 0.5 eV

15. Large mass effects

16. Theta_12 effect

17. Observability of relic neutrino w. T. Takahashi hep-ph/0703019
Pauli blocking effect

18. Magnitude of Pauli blocking

19. m_1 dependence for standard 1.9 K

20. Temperature measurement possible ?

21. 12 threhold

22. 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 ?

23. Measuring the lepton asymmetry
Definitive test of leptogenesis
Extremely difficult, (12) or (13) threshold most promissing

24. Experiments are not easy
Discovery of atomic pair emission
Mass measurement
M/D distinction
Relic detection

25. 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