The Hadronic Weak Interaction: Results, Opportunities and Challenges.

I give the results of two new experiments: the directional gamma asymmetry from polarized neutrons capturing on parahydrogen and the directional asymmetry of protons from the reaction of polarized neutrons with $^3$He. These and other parity violating (PV) asymmetries result from the weak interaction of nucleons, the hadronic weak interaction (HWI). In principal PV asymmetries are directly calculable from the standard model, but the difficulties of quantum chromodynamics put direct calculation beyond reach. I discuss two models which describe the HWI in terms of nuclear degrees of freedom: the meson exchange model introduced by Desplanques, Donoghue and Holstein and pionless effective field theory as developed by Schindler, Springer and Vanasse. The parameters of these models can be categorized according to expansions in 1/N$_c$, the number of colors. I discuss the results of efforts to extract the parameters of these models from available data and compare with the predictions of 1/N$_c$ expansions. There is qualitative agreement can be obtained my applying reasonable theoretical constraints that reduce the number of degrees of freedom. I argue that in order to make further progress experimental and theoretical work in exactly calculable systems is necessary. I discuss possible experiments in two and few-body systems.