Grant: Subatomic Physics Envelope - Project

This proposal supports the successful Canadian involvement of the internationally acclaimed Tokay to Kamiokande (T2K) long-baseline experiment. These measurements are important because they improve our understanding of remaining mysteries at the core of modern Physics including, among other things, the abundance of matter over antimatter in our universe.  During the period of this grant proposal (2023-2025) the T2K experiment expects to double the proton on target statistics which would at a minimum double the statistics in the event samples that have been collected over the past 10 years. This level of improvement is possible in such a short time because over the past year and a half the accelerator complex has undergone an extensive upgrade to the accelerator's power supplies, which means that the proton acceleration cycle time will be a factor of two faster, enabling instantaneous proton intensities of up to 750kW. T2K has been adding new final states to its signal event samples to improve sensitivity above simply increasing the neutrino flux.  In addition, in the past 2 years T2K's far detector, Super-Kamiokande (Super-K), has been doped with Gadolinium at 0.03% which improves its neutron detection efficiency by 50%. This enables several new lines of investigation to open, including possible neutrino-antineutrino discrimination at a statistical level. Taking advantage of this new sensitivity requires knowledge of neutrino interactions and an ability to constrain and accurately assess uncertainties in those neutrino interactions, one focus of the group supported here. The T2K-Canada group has played a key role in neutrino beamline instrumentation through the construction, commissioning, and operation of the Optical Transition Radiation (OTR) detector. These activities are continuing on through the next grant cycle where an upgraded OTR with a new set of foils and a new Data Acquisition System will be in operation. The OTR is a key component in keeping the neutrino beamline uncertainties small because the OTR measures the proton beam and spot size at a location closest to the target compared to any other proton monitor in the beamline. The T2K-Canada group has been improving measurements of neutrino interactions and the experiment's simulation of neutrino interactions. These improvements come both by analyzing T2K data and by also by developing new external inputs to cross sections and their uncertainties. These activities are beneficial in that they provide more information to refine the Standard Model and develop a window for seeing beyond it, while providing excellent opportunities for students and postdocs.  This group will design and build detector components, take data, analyze, and publish them in a few year time scale with a major impact on the neutrino oscillation analyses in T2K and Super-K.  With the funding from this grant, Canada can maintain its role as a major participant in this globally significant experiment.