The T2K experiment is a long baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle θ13θ13 by observing νeνe appearance in a νμνμ beam. It also aims to make a precision measurement of the known oscillation parameters, View the MathML sourceΔm232 and sin22θ23sin22θ23, via νμνμ disappearance studies. Other goals of the experiment include various neutrino cross-section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC. This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem

No abstract

No abstract

An extension of the TRIUMF M13 low-energy pion channel designed to suppress positrons based on an energy-loss technique is described. A source of beam channel momentum calibration from the decay π + → e + ν is also described.Key words: Beam channel, Particle separation, Pion Decay PACS: 41.85.Ja, 13.20.Cz, 29.27.Eg MotivationThe branching ratio of pion decays [1, 2], R=Γ(π → eν + eνγ)/Γ(π → µν + µνγ), has provided the best test of the hypothesis of electron-muon universality in weak interactions. The new TRIUMF PIENU experiment [3] aiming to improve the precision of the branching ratio measurement by a factor of five or more measures positrons from the π + → e + ν decay (E e + = 69.8 MeV) and the π + → µ + → e + decay chain (π + → µ + ν decay followed by µ + → e + νν decay, E e + < 52.8 MeV). In order to obtain maximum acceptance with minimum uncertainties arising from positron energy-dependent cross sections, the detector system involving a large NaI crystal is placed on the beam axis. Positrons in the beam (1/4 of the rate of pions) severely increase detector rates, trigger rates and background in the π + → e + ν spectrum. The TRIUMF M13 channel [4] has therefore been upgraded to suppress the positron contamination in the pion beam.

The quantity P π µ ξ, where ξ is one of the muon decay parameters and P π µ is the degree of muon polarization in pion decay, has been measured. The value P π µ ξ = 1.0003±0.0006 (stat.)±0.0038 (syst.) was obtained. This result agrees with previous measurements but is over a factor of two more precise. It also agrees with the Standard Model prediction for P π µ ξ and thus leads to restrictions on left-right symmetric models.