Abstract
A new event reconstruction algorithm based on a maximum likelihood method has been developed for Super-Kamiokande. Its improved kinematic and particle identification capabilities enable the analysis of atmospheric neutrino data in a detector volume 32% larger than previous analyses and increases sensitivity to the neutrino mass hierarchy. Analysis of a 253.9 kton-year exposure of the Super-Kamiokande IV atmospheric neutrino data has yielded a weak preference for the normal hierarchy, disfavoring the inverted hierarchy at 74% assuming oscillations at the best fit of the analysis.
Highlights
Neutrino oscillations have been confirmed by a variety of experiments using both natural and artificial sources
Since the processes of particle and optical photon propagation are decoupled from the response of the photomultiplier tubes (PMTs) and the electronics, the charge likelihood can be rewritten in terms of the expected number of photoelectrons produced at the i-th PMT given the hypothesis, μi(Γ, θ), as unhit hit
When the fiducial volume (FV) cut is near the wall cosmic ray background events might be introduced into the Fully Contained (FC) sample due to the vertex resolution of the reconstruction algorithm
Summary
Neutrino oscillations have been confirmed by a variety of experiments using both natural and artificial sources. Though most of its parameters have been experimentally measured[3], the ordering of the mass states with the largest splitting (known as the mass hierarchy), the octant of the atmospheric mixing angle θ23, and the value of its CP-violating phase are unknown. These unresolved issues have been at the forefront of results from the T2K [4], NOvA [5] and SuperKamiokande [6] (Super-K, SK) experiments and are the focus of next-generation experiments planned in the U.S [7], China [8], and Japan [9].
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