Parity mixing of the 0+-0- I=1 doublet in 14N
Abstract
We studied parity mixing of the 0+2,0-1; I=1 doublet in 14N (Ex~8.6 MeV) to probe the isoscalar component of the parity nonconserving (PNC) nucleon-nucleon interaction. The weak matrix element connecting the 0+ and 0- levels was determined by measuring the longitudinal analyzing power (AL) over the narrow Jπ=0+13C(p-->,p) resonance at Ep=1.16 MeV. Scattered protons were detected in two arrays of four scintillators arranged symmetrically about the beam axis at mean angles of FTHETA¯1=35° and FTHETA¯2=155°. The PNC signal was the difference in the longitudinal analyzing power observed at the two angles. Feedback loops were used to stabilize the position, angle, and spin direction of the beam on target. The observed signal was AL(FTHETA¯2)-AL(FTHETA¯1) =0.9+/-0.6×10-5 which corresponds to a weak matrix element <Hweak>=0.38+/-0.28 eV. Our measured <Hweak> disagrees with theoretical expectations; recent shell-model calculations by Horoi et al. using the PNC NN amplitudes of Desplanques, Donoghue, and Holstein yield <Hweak>'s that lie in the range from -0.2 eV to -0.8 eV. We briefly discuss some theoretical uncertainities that arise because the structure of the 14N doublet differs in important ways from other known parity doublets. In ancillary studies of the 13C(p,γ) reaction at θγ=90°, we found that the excitation energies and widths of the 0+ and 0- levels were (Ex=8624+/-2 keV, Γ=4.0+/-0.3 keV, and (Ex=8802+/-7 keV, Γ=440+/-8 keV) respectively. We also determined the following partial widths: Γγ(8624-->0)=(0.37+/-0.05) eV , Γγ(8624-->3948)=(1.26+/-0.17) eV, Γγ(8624-->5691)=(0.43+/-0.06) eV, Γγ(8624-->6204)=(2.03+/-0.28) eV, and Γγ(8802-->0)=(25.2+/-2.0) eV. We also report new parameters for the Ex=8062 keV, Ex=9174 keV, and Ex=9388 keV levels.
- Publication:
-
Physical Review C
- Pub Date:
- March 1995
- DOI:
- 10.1103/PhysRevC.51.1494
- Bibcode:
- 1995PhRvC..51.1494Z
- Keywords:
-
- 24.80.Dc;
- 27.20.+n;
- 21.30.+y;
- 24.70.+s;
- 6<
- =A<
- =19;
- Polarization phenomena in reactions