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 $(4.06\pm0.05)\times10^4$ cm$^{-2}$ normalized with $4\times10^{11}$ protons on target with 250 kA horn operation. The result is in agreement with the prediction which is corrected based on hadron production data.
Highlights
T2K consists of a neutrino beamline, producing an intense muon neutrino beam; a near detector complex, containing the INGRID on-axis detector and ND280 off-axis detector; and a far detector, Super-Kamiokande (Super-K)
Research Complex (J-PARC) is a facility situated in Tokai, Japan
The proton beam is transported to a graphite target every 2 to 3 seconds
Summary
T2K consists of a neutrino beamline, producing an intense muon neutrino beam; a near detector complex, containing the INGRID on-axis detector and ND280 off-axis detector; and a far detector, Super-Kamiokande (Super-K). The particles contributing to the signal at the muon monitor are estimated using the MC simulation where argon gas is used for the ionization chamber and all horn currents are set to 250 kA. The ionization chamber is calibrated by moving the entire chamber array by ±25 cm, which corresponds to the sensor spacing, in both the horizontal and vertical direction and measuring the muon profile at nine different configurations. All of the sensors are calibrated with a precision of 0.4% which is determined from the difference in the correction factors between the two data sets as described above. A correction factor was estimated using the MC simulation for the measurement of the vertical direction to account for this
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