Adding wavelength shifter molecules to the Sudbury Neutrino Observatory

This thesis provides a detailed study of the benefits of adding wavelength shifter molecules (WLS) to the heavy water of the Sudbury Neutrino Observatory (SNO). Their absorption and re-emission spectra allow the conversion of ultraviolet C˘erenkov photons into longer wavelength photons, that would be more easily detected. Measurements of the optical properties of five candidates show that only two of them, Alexa Fluor and Carbostyril, are suitable.

The analysis indicates that WLS would increase the number of detected photons, lead to more uniform distributions for the reconstructed position and energy, allow a larger fiducial volume and a lower energy threshold for the study of solar neutrinos. The goal is to determine whether adding WLS to SNO will allow a direct measurement of matter induced neutrino oscillations. Finally, a cosmic ray telescope has been developed and shows promising results for an independent measurement of the optical properties of WLS.