A study of relative efficiencies of photomultiplier tubes in the Sudbury Neutrino Observatory.

摘要

The Sudbury Neutrino Observatory (SNO) is a spherical heavy water Cerenkov-light detector built to understand neutrino physics. In particular it is credited with solving the "missing" solar neutrino problem. The SNO project uses a laser light with a diffuser, called a "laserball", to determine all the optical properties of the SNO detector from attenuation lengths in the water to individual photo-multiplier tube (PMT) characteristics. One such characteristic is the quantum efficiency, and it is the purpose of this study to investigate this quantity. A characteristic of laserball data is that one does not measure quantum efficiency but rather relative efficiencies. This thesis is a systematic analysis of the efficiencies extracted from pre-existing calibration code. Knowing the relative efficiencies increases the understanding of the detector's behavior in a previously unexamined area. Introduction of the PMT-to-PMT variations in efficiency into the pre-existing mathematical Monte-Carlo model of SNO has demonstrated better agreement between the observed and modeled energy resolution of the detector. The implications of this last Monte-Carlo adjustment may impact current published SNO results and further constrain theoretical models for neutrino oscillations.