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Title: Parity Violation in Neutron-Proton Capture -- The NPD Gamma Experiment

Abstract

The NPDGamma collaboration has recently completed the first phase of a measurement to determine the size of the weak nucleon-nucleon interaction from cold neutron capture on a liquid hydrogen target. In the framework of the nearly 30 year old DDH model [B. Desplanques, J.F. Donoghue, B.R. Holstein, Annals of Physics 124 (1980) 449], the measured process is explained in terms of the weak pion-nucleon coupling, while the framework of modern effective field theory parameterizes the measured process in terms of the {sup 3}S{sub 1}-{sup 3}P{sub 1}, long range transition (essentially the Danilov parameter {rho}{sub t}) [S.L. Zhu et al., Nuclear Physics A 748 (2005) 435; C.-P. Liu, Phys. Rev. C 75 (2007) 065501]. The couplings in terms of either model are directly proportional to the parity violating up-down asymmetry in the angular distribution of gamma rays with respect to the neutron spin direction in the reaction {rvec n} + p {yields} d + {gamma}. The asymmetry has a predicted size of 5 x 10{sup -8} and the aim of the NPDGamma collaboration is to measure it to 20%. The first phase of the measurement was completed at the Los Alamos National Laboratory Neutron Science Center Spallation Source with a preliminarymore » result of (-1.1 {+-} 2.1 stat. {+-} 0.2 sys.) x 10{sup -7}. Here, we report on the measurements and the results obtained so far. The experiment is currently being installed at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, for the remainder of its run time.« less

Authors:
 [1];  [2];  [3];  [2]
  1. University of Manitoba, Canada
  2. ORNL
  3. University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
979115
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 611; Journal Issue: 2-3
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ANGULAR DISTRIBUTION; ASYMMETRY; COLD NEUTRONS; HYDROGEN; LANL; NEUTRON SOURCES; NEUTRONS; NUCLEAR PHYSICS; ORNL; PARITY; PHYSICS; SPALLATION; SPIN

Citation Formats

Gericke, M. T., Bowman, James D, Greene, G. L., Penttila, Seppo I, and Collaboration, NPDGamma. Parity Violation in Neutron-Proton Capture -- The NPD Gamma Experiment. United States: N. p., 2009. Web. doi:10.1016/j.nima.2009.07.057.
Gericke, M. T., Bowman, James D, Greene, G. L., Penttila, Seppo I, & Collaboration, NPDGamma. Parity Violation in Neutron-Proton Capture -- The NPD Gamma Experiment. United States. https://doi.org/10.1016/j.nima.2009.07.057
Gericke, M. T., Bowman, James D, Greene, G. L., Penttila, Seppo I, and Collaboration, NPDGamma. Thu . "Parity Violation in Neutron-Proton Capture -- The NPD Gamma Experiment". United States. https://doi.org/10.1016/j.nima.2009.07.057.
@article{osti_979115,
title = {Parity Violation in Neutron-Proton Capture -- The NPD Gamma Experiment},
author = {Gericke, M. T. and Bowman, James D and Greene, G. L. and Penttila, Seppo I and Collaboration, NPDGamma},
abstractNote = {The NPDGamma collaboration has recently completed the first phase of a measurement to determine the size of the weak nucleon-nucleon interaction from cold neutron capture on a liquid hydrogen target. In the framework of the nearly 30 year old DDH model [B. Desplanques, J.F. Donoghue, B.R. Holstein, Annals of Physics 124 (1980) 449], the measured process is explained in terms of the weak pion-nucleon coupling, while the framework of modern effective field theory parameterizes the measured process in terms of the {sup 3}S{sub 1}-{sup 3}P{sub 1}, long range transition (essentially the Danilov parameter {rho}{sub t}) [S.L. Zhu et al., Nuclear Physics A 748 (2005) 435; C.-P. Liu, Phys. Rev. C 75 (2007) 065501]. The couplings in terms of either model are directly proportional to the parity violating up-down asymmetry in the angular distribution of gamma rays with respect to the neutron spin direction in the reaction {rvec n} + p {yields} d + {gamma}. The asymmetry has a predicted size of 5 x 10{sup -8} and the aim of the NPDGamma collaboration is to measure it to 20%. The first phase of the measurement was completed at the Los Alamos National Laboratory Neutron Science Center Spallation Source with a preliminary result of (-1.1 {+-} 2.1 stat. {+-} 0.2 sys.) x 10{sup -7}. Here, we report on the measurements and the results obtained so far. The experiment is currently being installed at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, for the remainder of its run time.},
doi = {10.1016/j.nima.2009.07.057},
url = {https://www.osti.gov/biblio/979115}, journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
number = 2-3,
volume = 611,
place = {United States},
year = {2009},
month = {1}
}