The goal of the NPDGamma experiment is to determine the parity-violating
asymmetry A gamma of
the correlation between the direction of
emission of the g ray and the neutron
polarization
in the reaction 
, which is expected to be of the order of 10-8.
Due
to the sensitivity of the deuteron to the long-range components of the
nucleon-nucleon interaction, Agamma
can be related to the weak meson-nucleon-nucleon couplings and is
dominated
by the isovector pion-nucleon-nucleon coupling H
pi 1. The reliable measurment of H
pi 1 will test the internal consistency of the
meson-exchange
picture of the weak nucleon-nucleon interaction and the modification of
the
effective strength of quark-quark neutral currents by QCD.
The work going on in Berkeley can be viewed here .
The experiment is
conducted at the Los Alamos Neutron Facility 
.