Parity nonconservation in 106Pd and 108Pd neutron resonances

Bret E. Crawford, Gettysburg College
J D. Bowman, Los Alamos National Laboratory
P P J. Delheij, TRIUMF
T Haseyama, Kyoto University
J N. Knudsen, Los Alamos National Laboratory
L Y. Lowie, North Carolina State University
A Masaike, Kyoto University
Y Matsuda, Kyoto University
G E. Mitchell, North Carolina State University
S I. Penttila, Los Alamos National Laboratory
H Postma, Delft University of Technology
N R. Roberson, Duke University
S J. Seestrom, Los Alamos National Laboratory
E I. Sharapov, Joint Institute for Nuclear Research
Sharon L. Stephenson, Gettysburg College
V W. Yuan, Los Alamos National Laboratory

Copyright held by American Physical Society. First published as BE Crawford et al, Parity nonconservation in 106Pd and 108Pd neutron resonances, Physical Review C, 60, 055503, doi: 10.1103/PhysRevC.60.055503.

Abstract

Parity nonconservation (PNC) has been studied in the neutron p-wave resonances of ¹⁰⁶Pd and ¹⁰⁸Pd in the energy range of 20 to 2000 eV. Longitudinal asymmetries in p-wave capture cross sections are measured using longitudinally polarized neutrons incident on ∼20-g metal-powder targets at LANSCE. A CsI γ-ray detector array measures capture cross section asymmetries as a function of neutron energy which is determined by the neutron time-of-flight method. A total of 21 p-wave resonances in ¹⁰⁶Pd and 21 p-wave resonances in ¹⁰⁸Pd were studied. One statistically significant PNC effect was observed in¹⁰⁶Pd, and no effects were observed in ¹⁰⁸Pd. For ¹⁰⁶Pd a weak spreading width of Γ_w=34_-28⁺⁴⁷×10^-7 eV was obtained. For ¹⁰⁸Pd an upper limit on the weak spreading width of Γ_w<12×10^-7 eV was determined at the 68% confidence level.