External Beta-Gamma Background Tails Analysis in SNO

The SNO collaboration is working on lowering its analysis energy threshold. To do this one must fully understand the background physics at these energies. At our anticipated threshold, MeV-order decay products from the Uranium and Thorium chain become increasingly important due to misreconstruction of these events, which allows them to pass our energy and fiducial volume cuts. Accordingly, one must study sources of beta-gamma radioactivity outside of our analysis region by expanding the fiducial volume. Using a newly developed energy fitter, position fitter, Monte Carlo simulations and new analysis techniques, the external backgrounds will be fit and the anticipated number of $\beta$-$\gamma$ external backgrounds in our signal box extrapolated.