Title: Into the Muck: Lowering the Energy Threshold of the Sudbury Neutrino Observatory


There are many motivations for probing the low energy regime of the solar neutrino spectrum: to see the rise in survival probability predicted by the MSW effect, to search for evidence of non-standard interactions with matter, or to determine whether sterile neutrinos play a role in neutrino oscillations. To date, however, the only spectrally-sensitive solar neutrino data sets come from water Cerenkov detectors, for which a recoil-electron energy threshold of 5~MeV has long been thought to be the only reasonably achievable lower limit. A new analysis underway at the Sudbury Neutrino Observatory (SNO) seeks to go as much as 1~MeV lower, although doing so requires significant improvements on many fronts: from detailed modelling of the detector down to the PMT and electronics level, removing backgrounds using timing-based and pattern recognition cuts, and improving the effective photon collection efficiency. I will discuss the problems faced by SNO's Low Energy Threshold Analysis and the solutions so far discovered, as well as the prospects for a low energy spectral measurement using data from both the earlier phases and the current phase of the experiment.