  The NPDGamma collaboration has constructed and commissioned an apparatus to
determine the size of the pion-nucleon coupling constant in the parity non
conserving pion exchange weak potential for N-N interactions. This coupling
constant is directly proportional to the parity violating up-down asymmetry in
the angular distribution of gamma rays with respect to the neutron spin
direction in the capture of polarized cold neutrons on protons. The measurement
of the weak pNN coupling will provide a test for the effective theory,
describing the nucleon-nucleon interaction as mediated by the exchange of
mesons, and provide results against which to compare models describing QCD at
low energy. NPDGamma is located at the Los Alamos Neutron Science Center
(LANSCE) and utilizes the special features of cold spallation neutrons to make
it possible to measure very small gamma ray asymmetries. In this paper, we
present the motivation for the experiment and report on experimental setup as
well as the current status of the project and the results obtained during the
2004 commissioning run including parity violation asymmetry measurements on Al,
CCL4, In, Boron-Carbide, and Cu.
