Non-standard neutrino interaction analysis with atmospheric neutrino data in Super-Kamiokande I-IV and the design of the Hyper-Kamiokande outer detector

Abstract

Neutrino oscillation is a well-established phenomenon and oscillation parameters are being measured with great accuracy. This unprecedented accuracy allows sensitivity to sub dominant effects which could indicate new physics. Nonstandard interactions (NSI) is a general term for interactions not described by the Standard Model. In this thesis NSIs are studied using 5326 days of Super-Kamiokande atmospheric neutrino data. This work focuses on NSIs which allow neutral current induced flavour transitions and interactions which allow different neutral current interaction amplitudes for different neutrino flavours. The strength of the NSI between neautrino flavours α and β is characterised by the parameter εαβ. A limit is obtained for the NSI strength, −0.046 < εµτ < 0.019 at 90% C.L., which is a slight improvement over the previous Super-K measurement and is consistent with recent IceCube measurements. Additional constraints on εeτ and εττ are obtained for different values of εee; the constraints in the e − τ sector are somewhat looser than previous Super-K measurements. Further improvements are expected with the next generation neutrino oscillation experiment Hyper-Kamiokande (Hyper-K). Hyper-K is a water Cherenkov detector which will make use of an outer detector to veto incoming charged particles and reduce backgrounds. This work details the design of the outer detector for Hyper-K, in particular research and development work carried out to enhance the light collection. Wavelength shifting plates are modelled and their efficiencies are studied. Reflective materials and their impact in the outer detector are also discussed.