A measurement of the parity violating asymmetry in the neutron capture on $^3$He at the SNS.

Studies of parity violating (PV) observables in hadronic systems offer a unique probe of nucleon structure, complementary to other probes of low-energy non-perturbative QCD. The n-$^3$He experiment at the Spallation Neutron Source at the ORNL measures the PV asymmetry of the recoil proton momentum $\vec{k}_p$ with respect to the neutron spin $\vec{\sigma}_n$ in the reaction $\rm n + {}^3He \to p + T + 764\,keV$. This asymmetry is sensitive to the isospin-conserving and isospin-changing ($\Delta$I = 0, 1) channels of the Hadronic Weak Interaction, and is expected to be extremely small ($\sim 10^{-7}$). The experiment will determine this PV asymmetry with the statistical sensitivity of the order of $10^{-8}$. Challenges like beam fluctuation, pedestal and background subtraction, instrumental interference, detector correlations and many others must be considered very carefully in the analysis to achieve this precision. I will discuss the data analysis and a method to extract the value for the PV asymmetry.