Measurement of the parity-odd angular distribution of γ rays from polarized neutron capture on Cl35

We report a measurement of two energy-weighted $\ensuremath{\gamma}$ cascade angular distributions from polarized slow neutron capture on the $^{35}\mathrm{Cl}$ nucleus, one parity-odd correlation proportional to $\stackrel{P\vec}{{s}_{n}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{P\vec}{{k}_{\ensuremath{\gamma}}}$ and one parity-even correlation proportional to $\stackrel{P\vec}{{s}_{n}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{P\vec}{{k}_{n}}\ifmmode\times\else\texttimes\fi{}\stackrel{P\vec}{{k}_{\ensuremath{\gamma}}}$. A parity-violating asymmetry can appear in this reaction due to the weak nucleon-nucleon interaction, which mixes opposite parity S- and P-wave levels in the excited compound $^{36}\mathrm{Cl}$ nucleus formed upon slow neutron capture. If parity-violating (PV) and parity-conserving (PC) terms both exist, the measured differential cross section can be related to them via $\frac{d\ensuremath{\sigma}}{d\mathrm{\ensuremath{\Omega}}}\ensuremath{\propto}1+{A}_{\ensuremath{\gamma},\mathrm{PV}}cos\ensuremath{\theta}+{A}_{\ensuremath{\gamma},\mathrm{PC}}sin\ensuremath{\theta}$. The PV and PC asymmetries for energy-weighted $\ensuremath{\gamma}$ cascade angular distributions for polarized slow neutron capture on $^{35}\mathrm{Cl}$ averaged over the neutron energies from 2.27--9.53 meV were measured to be ${A}_{\ensuremath{\gamma},\mathrm{PV}}=(\ensuremath{-}23.9\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and ${A}_{\ensuremath{\gamma},\mathrm{PC}}=(0.1\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. These results are consistent with previous experimental results. Systematic errors were quantified and shown to be small compared to the statistical error. These asymmetries in the angular distributions of the $\ensuremath{\gamma}$ rays emitted from the capture of polarized neutrons in $^{35}\mathrm{Cl}$ were used to verify the operation and data analysis procedures for the NPDGamma experiment, which measured the parity-odd asymmetry in the angular distribution of $\ensuremath{\gamma}$s from polarized slow neutron capture on protons.