skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Measurements of parity violation in a search for candidate resonances for a test of time-reversal invariance in neutron absorption

Abstract

Parity violation in neutron resonance absorption has been used in a search for candidate resonances for a new class of tests of time reversal invariance. Time reversal non-invariant effects in neutron absorption could be enhanced under the same conditions which lead to enhanced parity violation. This experiment therefore searched for parity violation in p-wave resonances to identify resonances appropriate for such time reversal test. The parity non-conserving cross section asymmetry P = ({sigma}{sub +} {minus} {sigma}{sub {minus}})/({sigma}{sub +} + {sigma}{sub {minus}}) was measured at resonances in four targets: {sup 155}Gd, {sup 165}Ho, {sup 235}U, and {sup 139}La. The experiment used a pulsed epithermal neutron beam and employed, for the first time, a spin-exchange optically-pumped polarized {sup 3}He neutron spin filter. Longitudinally polarized neutrons which passed through the sample were detected with a {sup 6}Li glass scintillator. A non-zero effect was observed at a 3.616 eV resonance in {sup 155}Gd: P = 1.2 {plus minus} 0.4%. Effects consistent with parity conservation were observed at a 5.6 eV resonance in {sup 165}Ho and a 0.290 eV resonance in {sup 235}U: P = 4.6 {plus minus} 4.0% and 0.1 {plus minus} 0.3%, respectively. The previously observed parity violation of P = 8.4 {plusmore » minus} 1.1% at the 0.734 eV resonance in {sup 139}La was used to assist in the measurement of the neutron polarization. In addition to reporting the results of this experiment, this dissertation discusses the enhancement mechanisms responsible for the large parity violating effects. It also describes the method of spin exchange optical pumping used to produce dense, gaseous targets of polarized {sup 3}He and such a target's use as a neutron spin filter. A review of the proposed time reversal tests, including the experimental configurations, the suggested enhancements, and the consequences of the measurements included in this work is given.« less

Authors:
Publication Date:
Research Org.:
Princeton Univ., NJ (United States)
OSTI Identifier:
5591721
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; GADOLINIUM 155 TARGET; NEUTRON REACTIONS; HOLMIUM 165 TARGET; LANTHANUM 139 TARGET; P INVARIANCE; NEUTRONS; RESONANCE ABSORPTION; T INVARIANCE; TESTING; URANIUM 235 TARGET; CROSS SECTIONS; P WAVES; RESONANCE; ABSORPTION; BARYON REACTIONS; BARYONS; ELEMENTARY PARTICLES; FERMIONS; HADRON REACTIONS; HADRONS; INVARIANCE PRINCIPLES; NUCLEAR REACTIONS; NUCLEON REACTIONS; NUCLEONS; PARTIAL WAVES; TARGETS; 663430* - Nucleon-Induced Reactions & Scattering- (1992-); 663560 - Nuclear Mass Ranges- A=90-149- (1992-); 663570 - Nuclear Mass Ranges- A=150-189- (1992-); 663590 - Nuclear Mass Ranges- A=220 & Above- (1992-); 662120 - General Theory of Particles & Fields- Symmetry, Conservation Laws, Currents & Their Properties- (1992-)

Citation Formats

Coulter, K P. Measurements of parity violation in a search for candidate resonances for a test of time-reversal invariance in neutron absorption. United States: N. p., 1989. Web.
Coulter, K P. Measurements of parity violation in a search for candidate resonances for a test of time-reversal invariance in neutron absorption. United States.
Coulter, K P. Sun . "Measurements of parity violation in a search for candidate resonances for a test of time-reversal invariance in neutron absorption". United States.
@article{osti_5591721,
title = {Measurements of parity violation in a search for candidate resonances for a test of time-reversal invariance in neutron absorption},
author = {Coulter, K P},
abstractNote = {Parity violation in neutron resonance absorption has been used in a search for candidate resonances for a new class of tests of time reversal invariance. Time reversal non-invariant effects in neutron absorption could be enhanced under the same conditions which lead to enhanced parity violation. This experiment therefore searched for parity violation in p-wave resonances to identify resonances appropriate for such time reversal test. The parity non-conserving cross section asymmetry P = ({sigma}{sub +} {minus} {sigma}{sub {minus}})/({sigma}{sub +} + {sigma}{sub {minus}}) was measured at resonances in four targets: {sup 155}Gd, {sup 165}Ho, {sup 235}U, and {sup 139}La. The experiment used a pulsed epithermal neutron beam and employed, for the first time, a spin-exchange optically-pumped polarized {sup 3}He neutron spin filter. Longitudinally polarized neutrons which passed through the sample were detected with a {sup 6}Li glass scintillator. A non-zero effect was observed at a 3.616 eV resonance in {sup 155}Gd: P = 1.2 {plus minus} 0.4%. Effects consistent with parity conservation were observed at a 5.6 eV resonance in {sup 165}Ho and a 0.290 eV resonance in {sup 235}U: P = 4.6 {plus minus} 4.0% and 0.1 {plus minus} 0.3%, respectively. The previously observed parity violation of P = 8.4 {plus minus} 1.1% at the 0.734 eV resonance in {sup 139}La was used to assist in the measurement of the neutron polarization. In addition to reporting the results of this experiment, this dissertation discusses the enhancement mechanisms responsible for the large parity violating effects. It also describes the method of spin exchange optical pumping used to produce dense, gaseous targets of polarized {sup 3}He and such a target's use as a neutron spin filter. A review of the proposed time reversal tests, including the experimental configurations, the suggested enhancements, and the consequences of the measurements included in this work is given.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1989},
month = {1}
}

Miscellaneous:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that may hold this item.

Save / Share: