Speaker
Michael Gericke
(University of Manitoba)
Description
The NPDGamma experiment has completed a measurement of the parity-violating directional gamma-ray asymmetry in the capture of cold neutrons on protons in a liquid hydrogen target. The asymmetry is directly related to the weak pion-nucleon coupling constant $h^1_{\pi}$, within the framework of the meson exchange model, and it is related to the effective field theory couplings $\tilde C^{\pi}_6$ and $m_N \rho_t$. The asymmetry has a predicted size of $-5\times 10^{-8} $, with large uncertainties in the theoretical prediction for the coupling constants. The goal precision of the measurement is $1\times 10^{-8}$, which would serve as the most precise constraint on the couplings in both theoretical frameworks. Since the asymmetry is a result of the interference between the weak and strong nucleon-nucleon forces, this measurement also provides an experimental benchmark for theoretical developments in the non-perturbative strong interaction regime. NPDGamma completed a two year long second phase run at the Spallation Neutron Source (SNS), at Oak Ridge National Laboratory and the final analysis is currently ongoing. I will provide an overview of the experiment, the analysis procedure, and some preliminary results.
Author
Michael Gericke
(University of Manitoba)
