On the Capability Of SuperKamiokande Detector To Define the Primary Parameters Of Muon And Electron Events

We develop a new discrimination procedure for separating electron neutrinos from muon neutrinos, based on detailed simulations carried out with GEANT 3.21 and with newly derived mean angular distribution functions for the charged particles concerned (muons and electrons/positrons), as well as the corresponding functions for the relative fluctuations. These angular distribution functions are constructed introducing a “moving point” approximation. Using our type definition procedure we are able to discriminate muons from electrons in Fully Contained Events with a probability of error of less than several %. At the same time, our geometrical reconstruction procedure, considering only the ring-like structure of the Cherenkov image, gives an unsatisfactory resolution for 1 GeV e and μ, with a mean vertex position error, δr, of 5–10m and a mean directional error, δθ, of about 6◦–20◦. In contrast, a geometrical reconstruction procedure utilizing the full image and using a detailed approximation of the event angular distribution works much better: for a 1 GeV e, δr ∼2m and δθ ∼3◦; for a 1 GeV μ, δr ∼3m and δθ ∼5◦. At 5 GeV, the corresponding values are ∼1.4m and ∼2◦ for e and ∼2.9m and ∼4.3◦ for μ. The numerical values depend on a single PMT contribution threshold. The values quoted above are the minima with respect to this threshold. Even the methodologically correct approach we have adopted, based on detailed simulations using closer approximations than those adopted in the SK analysis, cannot reproduce the accuracies for particle discrimination, momentum resolution, interaction vertex location, and angular resolution obtained by the SK simulations, suggesting the assumptions in these may be inadequate. PACS numbers: 13.15.+g, 14.60.-z