Letter of Intent: The Hyper-Kamiokande Experiment --- Detector Design and Physics Potential ---

Abstract

We propose the Hyper-Kamiokande (Hyper-K) detector as a next generation underground water Cherenkov detector. It will serve as a far detector of a long baseline neutrino oscillation experiment envisioned for the upgraded J-PARC, and as a detector capable of observing -far beyond the sensitivity of the Super-Kamiokande (Super-K) detector -proton decays, atmospheric neutrinos, and neutrinos from astronomical origins. The baseline design of Hyper-K is based on the highly successful Super-K, taking full advantage of a well-proven technology.Hyper-K consists of two cylindrical tanks lying side-by-side, the outer dimensions of each tank being 48 (W) × 54 (H) × 250 (L) m 3 . The total (fiducial) mass of the detector is 0.99 (0.56) million metric tons, which is about 20 (25) times larger than that of Super-K. A proposed location for Hyper-K is about 8 km south of Super-K (and 295 km away from J-PARC) at an underground depth of 1,750 meters water equivalent (m.w.e.). The inner detector region of the Hyper-K detector is viewed by 99,000 20-inch PMTs, corresponding to the PMT density of 20% photo-cathode coverage (one half of that of Super-K).Hyper-K presents unprecedented potential for precision measurements of neutrino oscillation parameters and discovery reach for CP violation in the lepton sector. With a total exposure of 5 years (one year being equal to 10 7 sec) to a 2.5-degree off-axis neutrino beam produced by the 1.66 MW J-PARC proton synchrotron, it is expected that the CP phase δ can be determined to better than 18 degrees for all possible values of δ and CP violation can be established with a statistical significance of 3σ for 74% of the δ parameter space if sin 2 2θ 13 > 0.03 and the mass hierarchy is known. If sin 2 2θ 13 is as large as 0.1 the mass hierarchy can be determined with more than 3σ statistical significance for 46% of the δ parameter space. In addition, a high statistics data sample of atmospheric neutrinos will allow us to extract the information on the mass hierarchy and the octant of θ 23 . With a full 10 year duration of data taking, the significance for the mass hierarchy determination is expected to reach 3σ or greater if sin 2 θ 23 > 0.4.Hyper-K can extend the sensitivity to nucleon decays beyond what was achieved by Super-K by an order of magnitude or more. The sensitivities to the partial lifetime of protons for the decay modes of p → e + π 0 and p → νK + are expected to exceed 1 × 10 35 years and 2 × 10 34 years, respectively. This is the only known, realistic detector option capable of reaching such a sensitivity for the p → e + π 0 mode.The scope of studies at Hyper-K also covers high precision measurements of solar neutrinos, observation of both supernova burst neutrinos and supernova relic neutrinos, dark matter searches, and possible detection of solar flare neutrinos. The prospects for neutrino geophysics using Hyper-K are also mentioned.

Measurement of neutrino-oxygen neutral-current quasi-elastic cross section using atmospheric neutrinos at Super-Kamiokande

“…The uncertainty in this measurement is dominated by systematic uncertainties including the atmospheric flux, cross section of other NC processes, primary and secondary process simulation, neutron simulation, as well as neutron-tagging efficiency. The flux measurement will improve with future Cherenkov detectors such as Hyper-Kamiokande [14]. The cross section for other NC processes can be improved by the T2K off-axis near detector ND280 [46,47] and other experiments such as Mini-BooNE [48] and MINERvA [49].…”

“…In this paper, we report the first measurement of the NCQE cross section on oxygen using atmospheric neutrinos. This measurement is particularly important for SRN searches in future water Cherenkov experiments such as SK-Gd [12,13] and Hyper-Kamiokande [14].…”

Dissipative Effect in Long Baseline Neutrino Experiments

“…In the near future there will be new long baselines experiments [1][2][3] to test the standard pattern of neutrino oscillation as never before. These experiments will have great sensitivity to determine the parameters that describe the standard oscillation pattern.…”

“…As the θ 13 value is not null, the three neutrino families will have to be taken into account in the new generation of long baseline experiments [1][2][3] as well as the MSW effect [37,38]. In this study, we will present a phenomenological approach where the most effective quantum dissipative operator will be defined to the case of three neutrino oscillations.…”

Proton Decay and Axion Dark Matter in SO(10) Grand Unification via Minimal Left-Right Symmetry

“…The future prospects is the expected exclusion limit at 90%C.L. of the Hyper-K (HK) experiment, 1.3 × 10 35 years [24], which is shown as the black dashed line. The figure shows that some of the parameter region with moderate coupling unification have been excluded by the current SK limit for M R 10 11.5 GeV (N E = 3).…”