Abstract
The NPDGamma collaboration reports results from the first phase of a measurement of the parity violating up-down asymmetry Aγ with respect to the neutron spin direction of γ rays emitted in the reaction n+p→d+γ using the capture of polarized cold neutrons on the protons in a liquid parahydrogen target. One expects parity-odd effects in the hadronic weak interaction between nucleons to be induced by the weak interaction between quarks. Aγ in n-+p→d+γ is dominated by a ΔI=1, 3S1-3P1 parity-odd transition amplitude in the n-p system. The first phase of the measurement was completed at the Los Alamos Neutron Science Center spallation source (LANSCE), with the result A γ=[-1.2±2.1(stat.)±0.2(sys.)]×10 -7. We also report the first measurement of an upper limit for the parity-allowed left-right asymmetry in this reaction, with the result A γ,LR=[-1.8±1.9(stat.)±0.2(sys.)]×10 -7. In this paper we give a detailed report on the theoretical background, experimental setup, measurements, extraction of parity-odd and parity-allowed asymmetries, analysis of potential systematic effects, and LANSCE results. The asymmetry has an estimated size of 5×10-8 and the aim of the NPDGamma collaboration is to measure it to 1×10-8. The second phase of the measurement will be performed at the Spallation Neutron Source at Oak Ridge National Laboratory.
| Original language | English (US) |
|---|---|
| Article number | 015505 |
| Journal | Physical Review C - Nuclear Physics |
| Volume | 83 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 31 2011 |
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ASJC Scopus subject areas
- Nuclear and High Energy Physics
Cite this
Measurement of parity-violating γ-ray asymmetry in the capture of polarized cold neutrons on protons. / Gericke, M. T.; Alarcon, Ricardo; Balascuta, S.; Barrón-Palos, L.; Blessinger, C.; Bowman, J. D.; Carlini, R. D.; Chen, W.; Chupp, T. E.; Crawford, C.; Covrig, S.; Dabaghyan, M.; Fomin, N.; Freedman, S. J.; Gentile, T. R.; Gillis, R. C.; Greene, G. L.; Hersman, F. W.; Ino, T.; Jones, G. L.; Lauss, B.; Leuschner, M.; Lozowski, W. R.; Mahurin, R.; Masuda, Y.; Mei, J.; Mitchell, G. S.; Muto, S.; Nann, H.; Page, S. A.; Penttilä, S. I.; Ramsay, W. D.; Salas-Bacci, A.; Santra, S.; Sharma, M.; Seo, P. N.; Sharapov, E. I.; Smith, T. B.; Snow, W. M.; Wilburn, W. S.; Yuan, V.
In: Physical Review C - Nuclear Physics, Vol. 83, No. 1, 015505, 31.01.2011.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Measurement of parity-violating γ-ray asymmetry in the capture of polarized cold neutrons on protons
AU - Gericke, M. T.
AU - Alarcon, Ricardo
AU - Balascuta, S.
AU - Barrón-Palos, L.
AU - Blessinger, C.
AU - Bowman, J. D.
AU - Carlini, R. D.
AU - Chen, W.
AU - Chupp, T. E.
AU - Crawford, C.
AU - Covrig, S.
AU - Dabaghyan, M.
AU - Fomin, N.
AU - Freedman, S. J.
AU - Gentile, T. R.
AU - Gillis, R. C.
AU - Greene, G. L.
AU - Hersman, F. W.
AU - Ino, T.
AU - Jones, G. L.
AU - Lauss, B.
AU - Leuschner, M.
AU - Lozowski, W. R.
AU - Mahurin, R.
AU - Masuda, Y.
AU - Mei, J.
AU - Mitchell, G. S.
AU - Muto, S.
AU - Nann, H.
AU - Page, S. A.
AU - Penttilä, S. I.
AU - Ramsay, W. D.
AU - Salas-Bacci, A.
AU - Santra, S.
AU - Sharma, M.
AU - Seo, P. N.
AU - Sharapov, E. I.
AU - Smith, T. B.
AU - Snow, W. M.
AU - Wilburn, W. S.
AU - Yuan, V.
PY - 2011/1/31
Y1 - 2011/1/31
N2 - The NPDGamma collaboration reports results from the first phase of a measurement of the parity violating up-down asymmetry Aγ with respect to the neutron spin direction of γ rays emitted in the reaction n+p→d+γ using the capture of polarized cold neutrons on the protons in a liquid parahydrogen target. One expects parity-odd effects in the hadronic weak interaction between nucleons to be induced by the weak interaction between quarks. Aγ in n-+p→d+γ is dominated by a ΔI=1, 3S1-3P1 parity-odd transition amplitude in the n-p system. The first phase of the measurement was completed at the Los Alamos Neutron Science Center spallation source (LANSCE), with the result A γ=[-1.2±2.1(stat.)±0.2(sys.)]×10 -7. We also report the first measurement of an upper limit for the parity-allowed left-right asymmetry in this reaction, with the result A γ,LR=[-1.8±1.9(stat.)±0.2(sys.)]×10 -7. In this paper we give a detailed report on the theoretical background, experimental setup, measurements, extraction of parity-odd and parity-allowed asymmetries, analysis of potential systematic effects, and LANSCE results. The asymmetry has an estimated size of 5×10-8 and the aim of the NPDGamma collaboration is to measure it to 1×10-8. The second phase of the measurement will be performed at the Spallation Neutron Source at Oak Ridge National Laboratory.
AB - The NPDGamma collaboration reports results from the first phase of a measurement of the parity violating up-down asymmetry Aγ with respect to the neutron spin direction of γ rays emitted in the reaction n+p→d+γ using the capture of polarized cold neutrons on the protons in a liquid parahydrogen target. One expects parity-odd effects in the hadronic weak interaction between nucleons to be induced by the weak interaction between quarks. Aγ in n-+p→d+γ is dominated by a ΔI=1, 3S1-3P1 parity-odd transition amplitude in the n-p system. The first phase of the measurement was completed at the Los Alamos Neutron Science Center spallation source (LANSCE), with the result A γ=[-1.2±2.1(stat.)±0.2(sys.)]×10 -7. We also report the first measurement of an upper limit for the parity-allowed left-right asymmetry in this reaction, with the result A γ,LR=[-1.8±1.9(stat.)±0.2(sys.)]×10 -7. In this paper we give a detailed report on the theoretical background, experimental setup, measurements, extraction of parity-odd and parity-allowed asymmetries, analysis of potential systematic effects, and LANSCE results. The asymmetry has an estimated size of 5×10-8 and the aim of the NPDGamma collaboration is to measure it to 1×10-8. The second phase of the measurement will be performed at the Spallation Neutron Source at Oak Ridge National Laboratory.
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U2 - 10.1103/PhysRevC.83.015505
DO - 10.1103/PhysRevC.83.015505
M3 - Article
VL - 83
JO - Physical Review C - Nuclear Physics
JF - Physical Review C - Nuclear Physics
SN - 0556-2813
IS - 1
M1 - 015505
ER -