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Title: Measurement of Parity-Violating y-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 A{sub {gamma}} with respect to the neutron spin direction of {gamma} rays emitted in the reaction n + p {yields} d + {gamma} 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. A{sub {gamma}} in n + p {yields} d + {gamma} is dominated by a {Delta}I = 1, {sup 3}S{sub 1-}{sup 3}P{sub 1} 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{sub {gamma}} = [-1.2 {+-} 2.1 (stat.) {+-} 0.2 (sys.)] x 10{sup -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{sub {gamma}LR} = [-1.8 {+-} 1.9 (stat.) {+-} 0.2 (sys.)] x 10{sup -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, andmore » LANSCE results. The asymmetry has an estimated size of 5 x 10{sup -8} and the aim of the NPDGamma collaboration is to measure it to 1 x 10{sup -8}. The second phase of the measurement will be performed at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Authors:
 [1];  [2];  [2];  [3];  [4]
  1. University of Manitoba, Canada
  2. ORNL
  3. Oak Ridge National Laboratory (ORNL)
  4. Collaboration
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1004678
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 83; Journal Issue: 1; Journal ID: ISSN 0556--2813
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; COLD NEUTRONS; NEUTRON SOURCES; NEUTRONS; NUCLEONS; ORNL; PARITY; PROTONS; QUARKS; SPALLATION; SPIN; TRANSITION AMPLITUDES; WEAK INTERACTIONS

Citation Formats

Gericke, M T, Bowman, James D, Greene, Geoffrey L, Penttila, Seppo, and NPD, Gamma. Measurement of Parity-Violating y-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, Bowman, James D, Greene, Geoffrey L, Penttila, Seppo, & NPD, Gamma. Measurement of Parity-Violating y-ray Asymmetry in the Capture of Polarized Cold Neutrons on Protons. United States. https://doi.org/10.1103/PhysRevC.83.015505
Gericke, M T, Bowman, James D, Greene, Geoffrey L, Penttila, Seppo, and NPD, Gamma. Sat . "Measurement of Parity-Violating y-ray Asymmetry in the Capture of Polarized Cold Neutrons on Protons". United States. https://doi.org/10.1103/PhysRevC.83.015505.
@article{osti_1004678,
title = {Measurement of Parity-Violating y-ray Asymmetry in the Capture of Polarized Cold Neutrons on Protons},
author = {Gericke, M T and Bowman, James D and Greene, Geoffrey L and Penttila, Seppo and NPD, Gamma},
abstractNote = {The NPDGamma collaboration reports results from the first phase of a measurement of the parity violating up-down asymmetry A{sub {gamma}} with respect to the neutron spin direction of {gamma} rays emitted in the reaction n + p {yields} d + {gamma} 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. A{sub {gamma}} in n + p {yields} d + {gamma} is dominated by a {Delta}I = 1, {sup 3}S{sub 1-}{sup 3}P{sub 1} 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{sub {gamma}} = [-1.2 {+-} 2.1 (stat.) {+-} 0.2 (sys.)] x 10{sup -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{sub {gamma}LR} = [-1.8 {+-} 1.9 (stat.) {+-} 0.2 (sys.)] x 10{sup -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 x 10{sup -8} and the aim of the NPDGamma collaboration is to measure it to 1 x 10{sup -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/1004678}, journal = {Physical Review C},
issn = {0556--2813},
number = 1,
volume = 83,
place = {United States},
year = {2011},
month = {1}
}