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Beta decay of exotic nuclei Pairing correlations
and weak-interaction studies
Bertram Blank CEN Bordeaux-Gradignan

• b-delayed 2p emission Pairing correlations
• Super-allowed b decays Weak interaction studies

TAS workshop, LPC Caen, 30-31 march 2004
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Beta-delayed two-proton emission Search for b2He
emission Proton-proton pairing far from stability
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Leaving the valley of stability.
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Two-proton radioactivity
Sequential emission Three-body decay
2He emission
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Known b2p emitters
Experimentelly observed b2p emitter
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b-delayed 2p emission 31Ar
ISOLDE facility
M.J.G. Borge, H.O.U. Fynbo, J. Thaysen et al.
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b-delayed 2p emission 31Ar
1st emitted
30S
Seq. Emission!!
29P
2nd emitted
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New experimenal setup for b2p emission
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New experimenal setup for b2p emission
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Candidates for the studies at SPIRAL
31Ar bp, b2p, b3p 26P bp, b2p 27S bp,
b2p, b3p 35Ca bp, b2p, b3p
31Ar production rates 10-20 pps ISOLDE 1-2 pps
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Super-allowed b decay Weak-interation studies CVC
and the CKM matrix
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From the ft value to the CKM matrix

• from Fermi b decay ft function of QEC, T1/2,
  BR
• Ft ? ft (1 dR) (1 dNS - dC)
• for T1
  transitions (e.g. 0 ? 0)
• Vud Gv / GF
  0.9740(5)
• ? (Vui)2 1 - ? unitarity?
• - before 2003 ? (Vui)2 0.9968(14) from
  nuclear b decay
• ? (Vui)2 0.9978(33)
  from neutron decay
• ? (Vui)2 0.9833(311)
  from pion decay
• - after 2003 Vus 0.2196(23)
  0.2272(28)
• ? (Vui)2 0.9999(16)

K 2 G2v (1DvR)
K 2 G2F (1DvR) Ft
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Present value of the corrected Ft value
, T 1
Ft 3072.2(8) s
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ft value and its corrections
dc correction
dR correction
Towner Hardy 2002
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62Ga half-life measurement at GSI

• ? Final statistical result 116.18(3) ms
• ? Final result 116.19(4) ms
• ? precision 3 10-4

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Ft for 62Ga

• T1/2 116.18(6) ms
• BR 99.8(1)
• QEC 9171(26) keV (Davids et al.)
• dR 1.46(9) (Towner Hardy)
• dNS dc 1.42(16) (Towner Hardy)
• ? ft (3056?48) s
• ? Ft (3056?48) s

Ft for 74Rb
? Ft (3103?28) s (Piechaczek et al.,
G. Ball et al.)
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Ft values and CVC
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Future measurements

• mass of 62Ga and 62Zn
• more precise mass of 74Rb (done at ISOLTRAP)
• more precise branching ratios for 62Ga (done at
  GSI/Jyväskylä)
• - 0 ? 02 transition
• - Gamow-Teller transitions
• 66As, 70Br
• 22Mg, 26Si, 30S, 34Ar (Texas AM)