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Title: Measurement of parity-violating γ-ray asymmetry in the capture of polarized cold neutrons on protons

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 Aγ=[-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 Aγ,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 Ridgemore » National Laboratory.« less

Authors:
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Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1007993
Report Number(s):
JLAB-THY-11-1310; DOE/OR/23177-1478
Journal ID: ISSN 0556-2813; PRVCAN; TRN: US1101329
DOE Contract Number:  
AC05-06OR23177
Resource Type:
Journal Article
Journal Name:
Physical Review. C, Nuclear Physics
Additional Journal Information:
Journal Volume: 83; Journal Issue: 1; Journal ID: ISSN 0556-2813
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; COLD NEUTRONS; LOS ALAMOS; NEUTRON SOURCES; NEUTRONS; NUCLEONS; ORNL; PARITY; PROTONS; QUARKS; SPALLATION; SPIN; TRANSITION AMPLITUDES; WEAK INTERACTIONS

Citation Formats

Gericke, M T, Balascuta, S, Barron-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, Penttila, 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, and Yuan, V. Measurement of parity-violating γ-ray asymmetry in the capture of polarized cold neutrons on protons. United States: N. p., 2011. Web. doi:10.1103/PhysRevC.83.015505.
Gericke, M T, Balascuta, S, Barron-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, Penttila, 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. Measurement of parity-violating γ-ray asymmetry in the capture of polarized cold neutrons on protons. United States. https://doi.org/10.1103/PhysRevC.83.015505
Gericke, M T, Balascuta, S, Barron-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, Penttila, 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, and Yuan, V. Sat . "Measurement of parity-violating γ-ray asymmetry in the capture of polarized cold neutrons on protons". United States. https://doi.org/10.1103/PhysRevC.83.015505.
@article{osti_1007993,
title = {Measurement of parity-violating γ-ray asymmetry in the capture of polarized cold neutrons on protons},
author = {Gericke, M T and Balascuta, S and Barron-Palos, L and Blessinger, C and Bowman, J D and Carlini, R D and Chen, W and Chupp, T E and Crawford, C and Covrig, S and Dabaghyan, M and Fomin, N and Freedman, S J and Gentile, T R and Gillis, R C and Greene, G L and Hersman, F W and Ino, T and Jones, G L and Lauss, B and Leuschner, M and Lozowski, W R and Mahurin, R and Masuda, Y and Mei, J and Mitchell, G S and Muto, S and Nann, H and Page, S A and Penttila, S I and Ramsay, W D and Salas-Bacci, A and Santra, S and Sharma, M and Seo, P -N and Sharapov, E I and Smith, T B and Snow, W M and Wilburn, W S and Yuan, V},
abstractNote = {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 Aγ=[-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 Aγ,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.},
doi = {10.1103/PhysRevC.83.015505},
url = {https://www.osti.gov/biblio/1007993}, journal = {Physical Review. C, Nuclear Physics},
issn = {0556-2813},
number = 1,
volume = 83,
place = {United States},
year = {2011},
month = {1}
}