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

March 22 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

March 22 Heidelberg 3 M vs D

March 22 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

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

March 22 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

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

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

March 22 Heidelberg 9 Rough estimate of rate

March 22 Heidelberg 10 Refinement

March 22 Heidelberg 11

March 22 Heidelberg 12 Majorana vs Dirac 6 channels available

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

March 22 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

March 22 Heidelberg 15

March 22 Heidelberg 16 Large mass effects

March 22 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

March 22 Heidelberg 18 Theta_12 effect

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

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

March 22 Heidelberg 21

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

March 22 Heidelberg 23 Magnitude of Pauli blocking

March 22 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

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

March 22 Heidelberg threshold Smaller effect with a larger rate

March 22 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 ?

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

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

March 22 Heidelberg 30 Level structure of candidate atom

March 22 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