Imperial Role on T2k
The Imperial group is a leading contributor to the T2K Oscillation Analysis working group, with a longstanding record of leadership. We have one current convener of this group as well as having had 4 group members be convener in the last 5 years. Our group contributes to both the far detector oscillation fit and the near detector fit.
The near detector analysis uses the high statistics ND280 data to tune and constrain the T2K neutrino interaction and flux models. These tuned models are then used to predict the expected event rate at the far detector without oscillation. The near detector fit reduces the uncertainty in this prediction from the 15% level to the 5% level.
The MaCh3 analysis applies Bayesian inference to the T2K oscillation analysis. The fitter itself is a Markov Chain Monte Carlo framework that aims to calculate the most likely value of the oscillation parameters, given our SK data and the ND280 prediction. The framework also allows more complex analyses, fitting both near and far detector data simultaneously, or incorporating additional freedom to investigate non-standard oscillation phenomena.
Alongside the oscillation analyses, the group has been heavily involved in the software and calibration of ND280. This is now being applied to the ND280 upgrade - new detectors that are planned to be installed in the ND280 facility in 2021. Imperial students have worked on the test beam program for the upgraded super-fine-grained detector, an array of 1cm scintillator cubes readout along each axis by wavelength shifting optic fibres. These upgrades promise exciting measurements in the coming years before Hyper-Kamiokande.
The group has a strong presence in the Neutrino Interaction Working Group (NIWG). Imperial students are currently improving the proton final state interaction and the pion production models used by T2K. This work will allow future oscillation analyses to incorporate pion and proton information, increasing the number of events observed at the far detector and reducing the uncertainties in the analysis.
Finally, the group has now started to become involved with the neutrino beamline. Current students developed the data acquisition system for the Optical Transition Radiation monitor, the most downstream beam monitor at T2K and a key part of the beam control and analysis. Another student is working on the simulation of the neutrino beamline optics, with the goal of understanding and reducing the beam loss in this area, leading to higher power beam operation.