A through-going muon produces plenty of Cherenkov light in the Super-Kamiokande neutrino detector
The T2K experiment is a second-generation long-baseline neutrino experiment utilising a 2.5o off-axis muon neutrino beam produced at the J-PARC accelerator complex in Tokai on the east coast of Japan. This 2.5o off-axis angle is chosen deliberately, as it produces a much more mono-energetic beam (peaked at 600 MeV) and maximises the expected neutrino oscillation probability. The neutrinos are first measured at a near detector complex built for the T2K experiment at J-PARC. The neutrinos then travel towards the existing Super-Kamiokande detector, located 295 km away in the mountains of western Japan.
The primary goal of over 400 physicists and 2000 engineers from the UK and around the world who combined forces to build the T2K experiment is to measure
of the mixing angle θ13 by measuring the oscillations from muon neutrinos to electron neutrinos. In 2011 the T2K collaboration announced that they had observed the first indication of this process and in 2013, with the addition of 3.5 times more data, it was firmly established.
Just as the T2K experiment can measure the appearance of electron neutrinos, it can also measure the disappearance of muon neutrinos as they travel from J-PARC to Super-Kamiokande. Therefore, an additional goal of T2K is to improve the measurement of the θ23 mixing parameter and the Δm223 mass difference. The 2017 results shown in the figure below demonstrate the world-leading constraint on these parameters.
The T2K near detectors are essential for controlling systematics on the oscillation analysis. The near detectors are used to characterise the beam profile and shape, the neutrino energy spectrum, measure the intrinsic electron neutrino contribution of the neutrino beam, and better understand neutrino-nucleon interactions.
Since 2014 the T2K experiment has taken data with both a neutrino and anti-neutrino beam, providing the first hints of CP violation. In the future, upgrades to T2K and the J-PARC accelerators (T2K-II) could lead to
measuring CP violation by comparing oscillations of neutrinos to
those of anti-neutrinos. These developments could aid the search for an
explanation as to why we don't see equal amounts of matter and
antimatter in the observable universe. The project will also use MPPCs (Multi-Pixel Photon
Counters) and is therefore helping to develop these.
The PPD group was actively involved in the construction and continues to be involved operation of the T2K experiment and T2K data analyses. The PPD played a leading role in the design and construction of the data acquisition system and the electronics used in the T2K near detector complex. The STFC Technology Department was also
involved in the data acquisition system, electronics and the design of the neutrino production target.