Overview of the T2K experiment
The T2K experiment investigates the nature of neutrinos and the way in which they change their identity from one type to another. Neutrinos are ghost-like particles that are produced in radioactive decays and they can pass through walls or even the entire earth without being stopped.
The experiment produces a beam of neutrinos at the J-PARC accelerator laboratory in Tokai, on the east coast of Japan. The neutrino beam is directed towards the Super Kamiokande detector, almost 300 km away, in Kamioka, as illustrated below. A tiny fraction of the neutrinos interact at the near detector complex (ND280) and at the far detector (SK). By comparing the neutrino beam properties before and after their long journey across Japan, we can study the way that neutrinos change from one type to another.
A short video describing the T2K experiment is found here.
VISPA and the ND280 Complex
The VIPSA T2K group has helped lead the design, construction, and operation of the near detectors. The ND280 detector is in an underground hall, in line with the SK detector, and is housed within a large magnet originally built for the UA1 experiment. A drawing and a photo of the detector half open are shown below:
VISPA and the ND280 Time Projection Chambers
The VISPA group leads the Time Projection Chambers (TPCs) project, which accurately measures charged particles produced by neutrino interactions in the detector - determining their momentum, charge and type. The TPCs are full of a gas that is ionized when particles pass through. The trail of ionization electrons is drifted towards sensitive readout modules, in order to record the path of the charged particles. The curvature of path, due to the magnetic field, determines the charge and momentum and the amount of ionization determines the particle type. The picture below shows Prof. Karlen standing near the TPCs that are suspended in the basket that holds the near detectors within the magnet. Also shown is an example picture of a neutrino event recorded by the near detector in 2010. The green tracks show the paths of the charged particles produced by a neutrino interacting in the Fine Grained Detector between the first and second TPC.
VISPA - T2K group
- Akira Konaka
- Anthony Hillairet
- Casey Bojechko
- Andre Gaudin
- Jordan Myslik
K. Abe, et al., First muon-neutrino disappearance study with an off-axis beam, Phys. Rev. D85, 031103(R) (2012).
K. Abe, et al., Indication of Electron Neutrino Appearance from an Accelerator-produced Off-axis Muon Neutrino Beam, Phys. Rev. Lett. 107, 041801 (2011).
N. Abgrall, et al., Time Projection Chambers for the T2K experiment, Nucl.Instrum.Meth. A637 (2011) 25-46.