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
March 22 2007 @ Heidelberg
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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
March 22 2007 @ Heidelberg
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M vs D
March 22 2007 @ Heidelberg
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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
March 22 2007 @ Heidelberg
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Majorana vs Dirac equations:chirally projected solutions
March 22 2007 @ Heidelberg
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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
March 22 2007 @ Heidelberg
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2 promissing atomic processes
• Low level metastable atoms laser irradiated
• Rydberg atoms microwave irradiated (not discussed here)
March 22 2007 @ Heidelberg
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Neutrino pair emission from laser irradiated metastable state
March 22 2007 @ Heidelberg
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Rough estimate of rate
March 22 2007 @ Heidelberg
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Refinement
March 22 2007 @ Heidelberg
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March 22 2007 @ Heidelberg
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Majorana vs Dirac
6 channels available
March 22 2007 @ Heidelberg
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Numerical estimate w.Y. Okabayashi• Input angles and masses: case of normal hierarchy
March 22 2007 @ Heidelberg
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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
March 22 2007 @ Heidelberg
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March 22 2007 @ Heidelberg
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Large mass effects
March 22 2007 @ Heidelberg
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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
March 22 2007 @ Heidelberg
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Theta_12 effect
March 22 2007 @ Heidelberg
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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
March 22 2007 @ Heidelberg
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Observability of relic neutrino w. T. Takahashi hep-ph/0703019
• Pauli blocking effect
March 22 2007 @ Heidelberg
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March 22 2007 @ Heidelberg
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• Crucial question
how large the “threshold ” region
March 22 2007 @ Heidelberg
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Magnitude of Pauli blocking
March 22 2007 @ Heidelberg
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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
March 22 2007 @ Heidelberg
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Temperature measurement possible ?
For m_1 < 1meV, temperature measurement is not difficult
March 22 2007 @ Heidelberg
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12 threshold
Smaller effect with a larger rate
March 22 2007 @ Heidelberg
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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 ?
March 22 2007 @ Heidelberg
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Measuring the lepton asymmetry• Definitive test of leptogenesis• Extremely difficult, (12) threshold most promissing
March 22 2007 @ Heidelberg
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Experiments are not easy: a possible strategy
• Discovery of atomic pair emission
• Mass measurement
• M/D distinction
• Relic detection
March 22 2007 @ Heidelberg
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Level structure of candidate atom
March 22 2007 @ Heidelberg
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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