Measurement of the muon beam direction and muon flux for the T2K neutrino experiment

Abstract

The Tokai-to-Kamioka (T2K) neutrino experiment measures neutrino oscillations by using an almost pure muon neutrino beam produced at the J-PARC accelerator facility. The T2K muon monitor was installed to measure the direction and stability of the muon beam which is produced together with the muon neutrino beam. The systematic error in the muon beam direction measurement was estimated, using data and MC simulation, to be 0.28 mrad. During beam operation, the proton beam has been controlled using measurements from the muon monitor and the direction of the neutrino beam has been tuned to within 0.3 mrad with respect to the designed beam-axis. In order to understand the muon beam properties, measurement of the absolute muon yield at the muon monitor was conducted with an emulsion detector. The number of muon tracks was measured to be (4.06 ± 0.05) × 10 4 cm −2 normalized with 4 × 10 11 protons on target with 250 kA horn operation. The result is in agreement with the prediction which is corrected based on hadron production data.

Measurement of neutrino and antineutrino oscillations by the T2K experiment including a new additional sample ofνeinteractions at the far detector

“…The outgoing hadrons decay in a 96-m-long decay volume, where a relatively pure beam of muon neutrinos is produced by the decay of positively charged hadrons in the positive focusing mode (ν mode), and a beam mostly composed of muon antineutrinos is produced in the negative focusing modeν mode). Protons and undecayed hadrons are stopped in a beam dump, while muons above 5 GeV pass through and are detected in a muon monitor (MUMON [14]) and are used to monitor the secondary beam stability. The T2K beamline hardware has been described in detail elsewhere [15].…”

Measurement of double-differential muon neutrino charged-current interactions onC8H8without pions in the final state using the

“…At the end of the decay volume, a beam dump stops the muons and remaining hadrons, leaving an almost pure muon neutrino beam with an intrinsic electron neutrino component of the order of a percent, which comes from the decays of kaons and muons, and an intrinsic muon antineutrino component of the order of 6% [33]. The beam stability and direction are monitored by the muon monitor [34,35] which measures the muons of energies higher than about 5 GeV that are able to penetrate the beam dump, and also by INGRID, the on-axis near detector, which samples the neutrino beam 280 m from the proton beam target [36].…”

Combined Analysis of Neutrino and Antineutrino Oscillations at T2K

“…Depending on the polarity of the horn current, either positively or negatively charged mesons are focused, resulting in a beam largely composed of muon neutrinos or antineutrinos. A 96-m decay volume lies downstream of the magnetic horns, followed by the beam dump and muon monitor [11]. The neutrino beam is measured by detectors placed on axis and off axis at 2.5°relative to the beam direction.…”