Background rejection for the neutrinoless double beta decay experiment SNO+

Thesis

The SNO+ experiment will use a liquid scintillator based detector to study solar, geo, and reactor neutrinos and double beta decay. This thesis discusses the effect of backgrounds on the measurement of neutrinoless double beta decay and describes analysis techniques developed to reduce their impact.

Details of the modeling of the photomultiplier tubes in the SNO+ Monte Carlo RAT are first described and comparisons are made with the SNO Monte Carlo SNOMAN. SNOMAN has been extensively verified with calibration sources and RAT is shown to be in good agreement. The event reconstruction techniques are then presented and predict an achievable 15cm position and 7% energy resolution.

The backgrounds are discussed and pileup backgrounds identified, including many previous unknown pileup backgrounds. Techniques to reject the pileup background are presented and shown to give over 99% rejection in the region of the double beta decay end point (3-4MeV), below the irreducible background from solar neutrinos. Finally the resulting limit on the effective Majorana neutrino mass SNO+ could achieve in 2015 is predicted to be 270meV and this is compared with other experiments that are underway.

Authors: Jones, PG

• Publication date: 2011
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: SNO+ Neutrino
• Subjects: Particle physics