Muon Capture Rates for Double Beta Decay

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Muon Capture Rates for Double Beta
Decay
?CR42?

• Status report

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?CR42?
(d,2He) PR C70(2004)
OMC
?
??
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What happens with muon in matter?
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µ-
3d -2p
4d -2p
2p -1s
3p -1s
4p -1s
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Two possible destinies of the muon stopped in a
target

• Beta-decay (both positive and negative)
• ?- ? ?? ?e e- (0
  - 50 MeV)
• Nuclear capture (only negative)
• ?- (A,Z) ? ?? (A, Z-1)
• 
  ?
• (A-1,
  Z-1) n (p,d,..)
• 
  ?
• (A-1,
  Z-1) ?

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Ordinary Muon Capture (OMC)
?CR42?

• Electron Capture
• e- (A,Z) ? (A, Z-1) ?e
• Q
  me ? 0.5 MeV
• Muon Capture
• ?- (A,Z) ? (A, Z-1) ??
• Q m?
  ? 100 MeV

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?CR42?
OMC
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?CR42?
95.8 -enriched Is available
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Nuclei candidates for measurement
?CR42?

• 2?-decaying nuclei
  48Ca, 150Nd, 96Zr, 100Mo, 82Se, 116Cd, 106Cd,
  130Te, 136Xe, 136Ce, 76Ge,
• Enriched targets availability
• (not available today) 100Ru
• (probably) 130Xe
• (sure) 48Ti, 76Se, 82Kr, 106Cd, 116Sn,
  150Sm

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Set-up
?CR42?
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PSI 2002, 2004
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PSI 2002, 2004
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PSI 2004, 2006
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Spectra measured with 48Ti target
Uncorrelated background
ng?4f
µX-rays (prompt)
nf?3d
nd?2p
np?1s
Nuclear ?-rays of interest (delayed)
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Time after µ-stop
Energy
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Time-evolution of a ?-line (method)
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Muon Life Time in 48Ti
370 keV
1297 keV
808 keV
767 keV
780 keV
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?CR42?
Total ?-Capture Rates
48Ca 5992 ns
40Ca 3622 ns
48Ti 3601 ns
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Partial OMC rates in 48Ti target
?CR42?
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Unfortunately,

• it is not the case for the 76Se, 106Cd,
  116Sn and 150Sm targets

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Failures and mistakes

• Detection system was optimized only for light
  targets. For the heavier we need
• Lower energy region (smaller Ge-detectors)
• Better timing (suppress µX-rays)
• Better E-resolution (instead of regular RF)
• Hot summer.
• We did not take enough care about temperature and
  voltage stability (separate feeding of
  acquisition electronics)

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Summer 2004

• 76Se, natSe, 106Cd, natCd remeasured with the
  above improvements (1 week per target)
  
• Gaseous 12C target failed.
• Solid 12C target measured, but useless
• Reason bad beam quality (µ e)
• Reason of the reason reconstruction

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Spectra measured with 76Se target
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Target 76Se
?-line 264.7 keV (75As)
?-line 279.5 keV (75As)
?-line 198.6 keV (75As)
Target natSe
?-line 109.6 keV (79As)
?-line 165.0 keV (76As)
?-line 215.5 keV (77As)
?-line 336.0 keV (81As)
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?-lines observed with 76Se target
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(Z,A)-dependence of the ?capture

• Primakoff rule
• ?c(Zeff)4 X1 1 - X2(A-Z)/2A
  
• X1 120..170
• X2 3.0

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2p3/2,1/2 ? 1s1/2 µX-transition in Cd target
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? -spectrum in 12C(?,? n)11B
2125
4445
5021
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Beam-time allocated in 2006 (?E4)

• 1 week SetUp
• 2 weeks 82Kr (for 2? of 82Se)
• 1 week 12C (C4H10?)