The Reliability on the Direction of the Incident Neutrino for the Fully Contained Events and Partially Contained Events due to QEL in the Super-Kamiokande

摘要

In the SK analysis of the neutrino events for [Fully Contained Events] and[Partially Contained Events] on their zenith angle distribution, it is assumedthat the zenith angle of the incident neutrino is the same as that of thedetected charged lepton. In the present paper, we examine the validity of [theSK assumption on the direction] of the incident neutrinos. Concretely speaking,we analyze muon-like events due to QEL. For the purpose, we develop [TimeSequential Monte Carlo Simulation] to extract the conclusion on the validity ofthe SK assumption. In our [Time Sequential Simulation], we simulate everyphysical process concerned as exactly as possible without any approximation. From the comparison between the zenith angle distributon of the emitted muonsunder [the SK assumption on the direction] and the corresponding one obtainedunder our [Time Sequential Simulation], it is concluded that the measurement ofthe direction of the incident neutrino for the neutrino events occurring insidethe detector in the SK analysis turns out to be unreliable, which holdsirrespective of the existence and/or non-existence of the neutrino oscillation.