Layout of the T2K Experiment where the neutrino beam travels from the east coast to western Japan
T2K is a long-baseline experiment at the forefront of neutrino physics, designed to investigate how neutrinos change from one flavour to another as they travel. The experiment will also help advance research about CP violation and the development of Multi-pixel Photon Counters (MPPCs), which are used to detect extremely weak light where extreme photo-detector sensitivity is needed, without being susceptible to magnetic fields.
For T2K, an intense beam of muon neutrinos is generated at the J-PARC nuclear physics site on the East coast of Japan and directed across the country to the Super-Kamiokande (Super-K) neutrino detector in the mountains of western Japan, 295km away. The beam is measured once before it leaves the J-PARC site, using the near detector ND280, and again at Super-K, a huge water Cherenkov detector (approximately 40m tall and 40m in diameter) built 1000m underground into the mountain rock. A water Cherenkov detector works by using photomultiplier tubes (PMTs) to observe rings of light emitted through the Cherenkov effect by charged particles moving in the ultrapure water, which lets the light travel almost unimpeded to the photodetectors. Even though T2K requires the Super-K detector to make its neutrino oscillation measurements, Super-K is a very important experiment in its own right, making many other measurements, for example using solar neutrinos and cosmic ray neutrinos.
The PPD neutrino group in collaboration with other UK institutes is helping develop the project.
ND280 DAQ SYSTEM
Historically, PPD has been instrumental in operating, maintaining, and upgrading the T2K ND280 near detector DAQ system and electronics. This has enabled T2K to take high-quality data that is used both for the oscillation analyses and the neutrino interactions cross-section measurements. The next ND280 upgrade phase requires updates to components of the DAQ, including elements of the software.
RAL provides the primary tape archive for the T2K near detector data and a Tier-2 site with disk storage and computing resources. The group is also working with the Computing Department to streamline the storage and processes involved for the future.
NEUTRINO CROSS-SECTION MEASUREMENTS
An important part of the T2K work at RAL focuses on neutrino cross-section measurements. The group is developing a new triple cross-section measurement, looking at the visible energy observed in the ND280 detector and developing more refined methods of energy estimation. The energy deposits from low momentum (under 450 MeV/c) protons can help in constraining one of the dominant sources of systematic uncertainty for measurements of oscillation parameters at T2K, which have never been measured at T2K.
This is why PPD with Lancaster university is working to develop a new photon analysis to identify photon events in the ND280 detector.