Abstract
Background: A previous measurement of the β-γ directional coefficient in Na22β decay was used to extract recoil-order form factors. The data indicate the requirement of a significant induced-tensor matrix element for the decay. This conclusion largely relies on a standard-model-allowed weak magnetism form factor which was determined using an unpublished value of the analog 21+→31+ γ branch in Na22, with the further assumption that the transition is dominated by its isovector M1 component. Purpose: Our aim is to determine the 21+→31+ width in Na22 in order to obtain an independent measurement of the weak magnetism form factor for the β decay. Methods: A Ne21(p,γ) resonance reaction on an implanted target was used to produce the first 2+ state in Na22 at Ex=1952 keV. Deexcitation γ rays were registered with two 100% relative efficiency high purity germanium detectors. Results: We obtain for the first time an unambiguous determination of the 21+→31+ branch in Na22 to be 0.45(8)%. Conclusions: Using the conserved vector current (CVC) hypothesis, our branch determines the weak magnetism form factor for Na22β decay to be |b/Ac1|=8.7(1.1). Together with the β-γ angular correlation coefficient, we obtain a large induced-tensor form factor for the decay that continues to disagree with theoretical predictions. Two plausible explanations are suggested.
| Language | English (US) |
|---|---|
| Article number | 035501 |
| Journal | Physical Review C |
| Volume | 95 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 15 2017 |
Profile
ASJC Scopus subject areas
- Nuclear and High Energy Physics
Cite this
21+ to 31+ γ width in Na 22 and second class currents 21+ to 31+ γ WIDTH in Na 22 ⋯ S. TRIAMBAK et al. / Triambak, S.; Phuthu, L.; García, A.; Harper, G. C.; Orce, J. N.; Short, D. A.; Steininger, S. P R; Diaz Varela, A.; Dunlop, R.; Jamieson, D. S.; Richter, W. A.; Ball, G. C.; Garrett, P. E.; Svensson, C. E.; Wrede, C.
In: Physical Review C, Vol. 95, No. 3, 035501, 15.03.2017.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - 21+ to 31+ γ width in Na 22 and second class currents 21+ to 31+ γ WIDTH in Na 22 ⋯ S. TRIAMBAK et al.
AU - Triambak,S.
AU - Phuthu,L.
AU - García,A.
AU - Harper,G. C.
AU - Orce,J. N.
AU - Short,D. A.
AU - Steininger,S. P R
AU - Diaz Varela,A.
AU - Dunlop,R.
AU - Jamieson,D. S.
AU - Richter,W. A.
AU - Ball,G. C.
AU - Garrett,P. E.
AU - Svensson,C. E.
AU - Wrede,C.
PY - 2017/3/15
Y1 - 2017/3/15
N2 - Background: A previous measurement of the β-γ directional coefficient in Na22β decay was used to extract recoil-order form factors. The data indicate the requirement of a significant induced-tensor matrix element for the decay. This conclusion largely relies on a standard-model-allowed weak magnetism form factor which was determined using an unpublished value of the analog 21+→31+ γ branch in Na22, with the further assumption that the transition is dominated by its isovector M1 component. Purpose: Our aim is to determine the 21+→31+ width in Na22 in order to obtain an independent measurement of the weak magnetism form factor for the β decay. Methods: A Ne21(p,γ) resonance reaction on an implanted target was used to produce the first 2+ state in Na22 at Ex=1952 keV. Deexcitation γ rays were registered with two 100% relative efficiency high purity germanium detectors. Results: We obtain for the first time an unambiguous determination of the 21+→31+ branch in Na22 to be 0.45(8)%. Conclusions: Using the conserved vector current (CVC) hypothesis, our branch determines the weak magnetism form factor for Na22β decay to be |b/Ac1|=8.7(1.1). Together with the β-γ angular correlation coefficient, we obtain a large induced-tensor form factor for the decay that continues to disagree with theoretical predictions. Two plausible explanations are suggested.
AB - Background: A previous measurement of the β-γ directional coefficient in Na22β decay was used to extract recoil-order form factors. The data indicate the requirement of a significant induced-tensor matrix element for the decay. This conclusion largely relies on a standard-model-allowed weak magnetism form factor which was determined using an unpublished value of the analog 21+→31+ γ branch in Na22, with the further assumption that the transition is dominated by its isovector M1 component. Purpose: Our aim is to determine the 21+→31+ width in Na22 in order to obtain an independent measurement of the weak magnetism form factor for the β decay. Methods: A Ne21(p,γ) resonance reaction on an implanted target was used to produce the first 2+ state in Na22 at Ex=1952 keV. Deexcitation γ rays were registered with two 100% relative efficiency high purity germanium detectors. Results: We obtain for the first time an unambiguous determination of the 21+→31+ branch in Na22 to be 0.45(8)%. Conclusions: Using the conserved vector current (CVC) hypothesis, our branch determines the weak magnetism form factor for Na22β decay to be |b/Ac1|=8.7(1.1). Together with the β-γ angular correlation coefficient, we obtain a large induced-tensor form factor for the decay that continues to disagree with theoretical predictions. Two plausible explanations are suggested.
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U2 - 10.1103/PhysRevC.95.035501
DO - 10.1103/PhysRevC.95.035501
M3 - Article
VL - 95
JO - Physical Review C - Nuclear Physics
T2 - Physical Review C - Nuclear Physics
JF - Physical Review C - Nuclear Physics
SN - 0556-2813
IS - 3
M1 - 035501
ER -