Plans and Status of Hyper-Kamiokande

One of the important unknowns in neutrino oscillation physics is the leptonic CP phase $\delta_{CP}$. Because of the ambiguity between $\delta_{CP}$ and neutrino mass hierarchy, experiments have to be designed in such a way as to measure these parameters independent of each other. Long baseline experiments like DUNE is exclusively designed to measure $\delta_{CP}$ in regions without hierarchy ambiguity and atmospheric neutrino experiments like INO are designed to measure hierarchy without $\delta_{CP}$ ambiguity. However atmospheric neutrinos are not usually used to probe $\delta_{CP}$. Here we present that, sub--GeV energy atmospheric neutrinos can be used to probe $\delta_{CP}$ irrespective of mass hierarchy. We show that when the events are binned as a function of $(E^{\rm{obs}}_l,\cos\theta^{\rm{obs}}_l)$, the observed energy and direction of the final state leptons in charged current interactions of $\nu$ and $\overline{\nu}$, a consistent distinction between various $\delta_{CP}$ values is obtained. Since there is no sensitivity to the mass ordering/hierarchy, $\delta_{CP}$ can be measured without hierarchy ambiguity at these energies. Sensitivity studies with ideal as well as realistic cases are discussed.

We describe the effects of neutrino propagation in the matter of the Earth relevant to experiments with atmospheric and accelerator neutrinos and aimed at the determination of the neutrino mass hierarchy and CP violation. These include (i) the resonance enhancement of neutrino oscillations in matter with constant or nearly constant density, (ii) adiabatic conversion in matter with slowly changing density, (iii) parametric enhancement of oscillations in a multilayer medium, and (iv) oscillations in thin layers of matter. We present the results of semianalytic descriptions of flavor transitions for the cases of small density perturbations, in the limit of large densities and for small density widths. Neutrino oscillograms of the Earth and their structure after determination of the 1–3 mixing are described. A possibility to identify the neutrino mass hierarchy with the atmospheric neutrinos and multimegaton scale detectors having low energy thresholds is explored. The potential of future accelerator experiments to establish the hierarchy is outlined.

Measurements of atmospheric, solar, reactor and accelerator neutrinos (see e.g. [1, 2, 3, 4]) have shown that neutrinos undergo flavour-changing oscillations and hence have mass. The cubic-kilometre neutrino detector IceCube [5] with its more densely instrumented inner region DeepCore [6] has studied oscillations of atmospheric neutrinos at energies above ∼ 10 GeV [7, 8, 9]. The Precision IceCube Next Generation Upgrade (PINGU) [10] is a proposed extension of IceCube with the goal to perform precise measurements of atmospheric neutrino oscillations down to a few GeV and to determine the neutrino mass hierarchy (NMH).

The relatively large measured value of $\theta_{13}$ has opened up the possibility of determining the neutrino mass hierarchy through earth matter effects. Amongst the current accelerator-based experiments only NOvA has a long enough baseline to observe earth matter effects. However, NOvA is plagued with uncertainty on the knowledge of the true value of $\delta_{CP}$, and this could drastically reduce its sensitivity to the neutrino mass hierarchy. The earth matter effect on atmospheric neutrinos on the other hand is almost independent of $\delta_{CP}$. The 50 kton magnetized Iron CALorimeter at the India-based Neutrino Observatory (ICAL@INO) will be observing atmospheric neutrinos. The charge identification capability of this detector gives it an edge over others for mass hierarchy determination through observation of earth matter effects. We study in detail the neutrino mass hierarchy sensitivity of the data from this experiment simulated using the Nuance based generator developed for ICAL@INO and folded with the detector resolutions and efficiencies obtained by the INO collaboration from a full Geant4-based detector simulation. The data from ICAL@INO is then combined with simulated data from T2K, NOvA, Double Chooz, RENO and Daya Bay experiments and a combined sensitivity study to the mass hierarchy is performed. With 10 years of ICAL@INO data combined with T2K, NOvA and reactor data, one could get about $2.3\sigma-5.7\sigma$ discovery of the neutrino mass hierarchy, depending on the true value of $\sin^2\theta_{23}$ [0.4 -- 0.6], $\sin^22\theta_{13}$ [0.08 -- 0.12] and $\delta_{CP}$ [0 -- 2$\pi$].

We present the latest results from Super-Kamiokande (SK) for solar, atmospheric and supernova neutrinos. SK has been operating for about 16 years, accumulating the highest statistics of the neutrino event data. The flux and energy spectrum as well as the day/night flux asymmetry of solar neutrinos have been measured precisely. We find the day/night flux asymmetry with the 2.7σ significance, indicating that the electron neutrino regeneration may occur in the earth. The recent discovery of the finite θ13 value motivates us to explore the determination of the neutrino mass hierarchy, θ23 octant and a CP-violating phase using atmospheric neutrinos. SK also has found the appearance of τ neutrinos with the 3.8σ significance in the atmospheric neutrino data sample. The neutrino oscillation parameters are determined based on the solar and atmospheric neutrino measurements. SK has the highest sensitivity to the supernova relic neutrinos that have been accumulated in the universe as a result of the past supernova explosions. We report the latest result of a search for the supernova relic neutrinos. We also mention about the current R&D status of a Gd-loaded water Cherenkov detector.

Mass and CKM matrices of quarks and leptons, the leptonic CP-phase in neutrino oscillations

1149 POSTER Recombinant lectin ATL-104 reduces the duration and severity of intestinal epithelial damage caused by 5-fluorouracil in rats

GLoBES: General Long Baseline Experiment Simulator

and survival probabilities relevant to atmospheric neutrino and very long baseline (> 4000 Km) beam experiments. The inter-relations between the three probabilities Pµe, Pµτ and Pµµ are examined. It is shown that large and observable sensitivity to the neutrino mass hierarchy can be present in Pµµ and Pµτ. We emphasize that at baselines of> 7000 Km, matter effects in Pµτ are important under certain conditions and can be large. The muon survival rates in experiments with very long baselines thus depend on matter effects in both Pµτ and Pµe. We also indicate where these effects provide sensitivity to θ13, and identify ranges of energies and baselines where the event rates increase with decreasing θ13, providing a useful handle to probe small values of this parameter. The effect of parameter degeneracies in the three probabilities at these baselines and energies is studied in detail and large parts of the parameter space are identified which are free from these degeneracies. In the second part of the paper, we focus on using the matter effects studied in the first part as a means of determining the mass hierarchy via atmospheric neutrinos. Realistic event rate calculations are performed for a charge discriminating 100 kT iron calorimeter

We explore a possibility to measure the CP-violating phase δ using multimegaton scale ice or water Cherenkov detectors with low, (0.2-1) GeV, energy threshold assuming that the neutrino mass hierarchy is identified. We elaborate the relevant theoretical and phenomenological aspects of this possibility. The distributions of the ν μ (track) and ν e (cascade) events in the neutrino energy and zenith angle (E ν − θ z ) plane have been computed for different values of δ. We study properties and distinguishability of the distributions before and after smearing over the neutrino energy and zenith angle. The CP-violation effects are not washed out by smearing, and furthermore, the sensitivity to δ increases with decrease of the energy threshold. The ν e events contribute to the CP-sensitivity as much as the ν μ events. While sensitivity of PINGU to δ is low, we find that future possible upgrade, Super-PINGU, with few megaton effective volume at (0.5-1) GeV and e.g. after 4 years of exposure will be able to disentangle values of δ = π/2, π, 3π/2 from δ = 0 with “distinguishability” (∼ significance in σ’s) S tot = (3 − 8), (6 − 14), (3 − 8) correspondingly. Here the intervals of S σot are due to various uncertainties of detection of the low energy events, especially the flavor identification, systematics, etc. Super-PINGU can be used simultaneously for the proton decay searches.

Super-Kamiokande is a large water Cerenkov detector which consists of 50 kton pure water as a target of observation of atmospheric, solar, supernovae and accelerator neutrino and as a source of nucleon decay. Cherenkov lights emitted by charged particles from neutrino interaction at 22.5 kton of ducial volume are viewed by 11,146 inward-facing 20-inch photomultiplier tubes(PMTs) during the rst run of the detector, SK-I. The two subsequent run periods, SK-II and SK-III had 5,182 and 11,129 PMTs respectively. The outer detector surrounding the inner volume has been instrumented with 1,885 outward-facing 8-inch PMTs and used primarily as a veto. Although Super-Kamiokande has provided enormous amount of data and physics results [1] for more than 10 years since the observation started in 1996, DAQ electronics and computers are upgraded in September 2008. There are several motivations from physics to upgrade the electronics and online system. A wider charge dynamic range enables us improvement of energy resolution of high energy atmospheric neutrino events. A trigger window with much longer time enables us to improve muon decay electron nding ef ciency in atmospheric neutrino study and nucleon decay search. After the commissioning of new DAQ system, intensive calibration works have been performed, then, SK started its physics data taking as SK-IV in October 2008. In the paper, atmospheric neutrino oscillation analysis results from SK-I+II+III (before electronics upgrade) data on standard 2avor oscillation, 3avor oscillation with normal and inverted hierarchy, and search for CPT violation, and Early data of atmospheric neutrino from SK-IV are reported.

Neutrino oscillations, first measured in 1998 via atmospheric neutrinos, have provided the only current direct evidence for physics beyond the Standard Model of Elementary Particles. The full neutrino mixing, described by six parameters, has been measured in the last decade with the exception of the charge-parity phase and the ordering of the mass eigenstates (the neutrino mass hierarchy – NMH). A relatively large mixing-angle between the first and third mass eigenstates has opened the possibility of measuring the mass hierarchy via atmospheric neutrinos using very large volume detectors. A leading proposal to perform this measurement is the future low-energy extension to the IceCube–DeepCore detector, called PINGU (the Precision IceCube Next Generation Upgrade). By increasing the photocathode density in the DeepCore region, it is possible to lower the energy threshold in the fiducial volume to the region that is affected by the MSW [1, 2], and thus permits extraction of the hierarchy. Here we discuss the design of the PINGU detector, its sensitivity to the mass hierarchy (approximately 3σ in 3.5 years) and measurements of νμ disappearance and ντ appearance.

An analysis of atmospheric neutrino data from all four run periods of Super-Kamiokande optimized for sensitivity to the neutrino mass hierarchy is presented. Confidence intervals for Δ m 2 32 , sin 2 θ 23 , sin 2 θ 13 and δ C P are presented for normal neutrino mass hierarchy and inverted neutrino mass hierarchy hypotheses, based on atmospheric neutrino data alone. Additional constraints from reactor data on θ 13 and from published binned T2K data on muon neutrino disappearance and electron neutrino appearance are added to the atmospheric neutrino fit to give enhanced constraints on the above parameters. Over the range of parameters allowed at 90% confidence level, the normal mass hierarchy is favored by between 91.9% and 94.5% based on the combined Super-Kamiokande plus T2K result.

We examine the potential for a ``natural'' three-neutrino mixing scheme to satisfy available data and astrophysical arguments. By ``natural'' we mean no sterile neutrinos, and a neutrino mass hierarchy similar to that of the charged leptons. We seek to satisfy (or solve): 1. Accelerator and reactor neutrino oscillation constraints, including LSND; 2. The atmospheric muon neutrino deficit problem; 3. The solar neutrino problem; 4. Supernova $r$-process nucleosynthesis in neutrino-heated supernova ejecta; 5. Cold+hot dark matter models. We argue that putative supernova $r$-process nucleosynthesis bounds on two-neutrino flavor mixing can be applied directly to three-neutrino mixing in the case where one vacuum neutrino mass eigenvalue difference dominates the others. We show that in this ``one mass scale dominance'' limit, a natural three-neutrino oscillation solution meeting all the above constraints exists only if the atmospheric neutrino data {\em and} the LSND data can be explained with one neutrino mass difference. In this model, an explanation for the solar neutrino data can be effected by employing the {\em other} independent neutrino mass difference. Such a solution is only marginally allowed by the current data, and proposed long-baseline neutrino oscillation experiments can definitively rule it out. If it were ruled out, the simultaneous solution of the above constraints by neutrino oscillations would then require sterile neutrinos and/or a neutrino mass hierarchy of a different nature than that of the charged leptons.

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.