Majorana neutrino spectroscopy and measuring relic neutrino M. Yoshimura

March 22 2007 @ Heidelberg

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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


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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


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M vs D


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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


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Majorana ｖｓ　 Dirac equations:chirally projected solutions


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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


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2 promissing atomic processes

• Low level metastable atoms laser irradiated

• Rydberg atoms microwave irradiated (not discussed here)


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Neutrino pair emission from laser irradiated metastable state


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Rough estimate of rate


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Refinement


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Majorana vs Dirac

6 channels available


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Numerical estimate w.Y. Okabayashi• Input angles and masses: case of normal hierarchy


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massless

Majorana

Red

massless

Dirac

Blue 80.50~ 0.9 (meV)0.1 321 mmm

50.8~ 9.2~ (meV)0.2 321 mmm 50.9~ 4.9~ (meV)0.3 321 mmm 51.0~ 8.9~ (meV)0.4 321 mmm

Mass varied 032.0~213s3.0~56.0~ 22

12s

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

0.51~ 2.10~ (meV)0.5 321 mmm

1.51~ 8.10~ (meV)0.6 321 mmm


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Large mass effects


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massless

Majorana

Red

massless

Dirac

Blue

80.50~ 0.9 (meV)0.1 321 mmm

Mixing angle varied 0 3.0~ 213

212 ss032.0~ 3.0~ 2

13212 ss

032.0~ 35.0~ 213

212 ss 032.0~ 28.0~ 2

13212 ss

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


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Theta_12 effect


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Case of inverted mass hierarchy

8.50~ 0.50~ (meV)0.1 321 mmm

①

① ②

③ ④

⑤ ⑥

②

8.50~ 0.50 (meV)5.0 321 mmm

③

8.50~ 0.50 (meV)1.0 321 mmm

④0.52~ 0.51~ (meV)0.10 321 mmm

⑤0.112~ 0.112~ (meV)0.100 321 mmm

⑥0.503~ 0.503~ (meV)0.500 321 mmm


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Observability of relic neutrino w. T. Takahashi hep-ph/0703019

• Pauli blocking effect


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• Crucial question

how large the “threshold ” region


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Magnitude of Pauli blocking


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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


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Temperature measurement possible ?

For m_1 < 1meV, temperature measurement is not difficult


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12 threshold

Smaller effect with a larger rate


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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 ?


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Measuring the lepton asymmetry• Definitive test of leptogenesis• Extremely difficult, (12) threshold most promissing


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Experiments are not easy: a possible strategy

• Discovery of atomic pair emission

• Mass measurement

• M/D distinction

• Relic detection


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Level structure of candidate atom


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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

Documents

Majorana neutrino spectroscopy and measuring relic neutrino M. Yoshimura