arXiv subjects

K. Tateishi

Publications and source records attributed to K. Tateishi.

5 recordsLinked to original sources

arXiv2025

Radiation-tolerant polarized solid target

Polarized targets evolved into indispensable tools in particle and nuclear physics. However, the polarized solid target is degraded by high-intense beam irradiation, known as radiation damage due to target heating and radical generation. We demonstrated a radiation-tolerant polarized solid target operating at room temperature. An annealing allows the spontaneous repair of the damage by reducing unwanted radicals. Using a single crystal of $\it p$-terphenyl doped with 0.01 mol\% pentacene-$\it d$$_{14}$, Dynamic Nuclear Polarization using photoexcited triplet electrons (Triplet-DNP) was applied to proton spins at room temperature and in 0.39 T. For the proof of concept, a deuteron beam with an energy of 135 MeV/u and the intensities of 10$^7$-10$^9$ counts per second (cps) was irradiated. The proton polarization was determined to be 3.0\% $\pm$0.2\%$\rm{(stat.)}$ $\pm$0.1\%$\rm {(sys.)}$ from a scattering asymmetry. The polarization was almost not attenuated up to 10$^9$ cps, but the target crystal was yellowed. The visible-light absorption spectroscopy suggested irreversible radiation damage due to missing protons by the knock-out reaction. The room-temperature polarized solid target allows impractical experiments with the conventional target system, leading to a next-generation spin-dependent accelerator science.

physics.ins-det↗

arXiv2016

Real-Time Supernova Neutrino Burst Monitor at Super-Kamiokande

We present a real-time supernova neutrino burst monitor at Super-Kamiokande (SK). Detecting supernova explosions by neutrinos in real time is crucial for giving a clear picture of the explosion mechanism. Since the neutrinos are expected to come earlier than light, a fast broadcasting of the detection may give astronomers a chance to make electromagnetic radiation observations of the explosions right at the onset. The role of the monitor includes a fast announcement of the neutrino burst detection to the world and a determination of the supernova direction. We present the online neutrino burst detection system and studies of the direction determination accuracy based on simulations at SK.

astro-ph.HE↗

arXiv2015

Limits on sterile neutrino mixing using atmospheric neutrinos in Super-Kamiokande

We present limits on sterile neutrino mixing using 4,438 live-days of atmospheric neutrino data from the Super-Kamiokande experiment. We search for fast oscillations driven by an eV$^2$-scale mass splitting and for oscillations into sterile neutrinos instead of tau neutrinos at the atmospheric mass splitting. When performing both these searches we assume that the sterile mass splitting is large, allowing $\sin^2(Δm^2 L/4E)$ to be approximated as $0.5$, and we assume that there is no mixing between electron neutrinos and sterile neutrinos ($|U_{e4}|^2 = 0$). No evidence of sterile oscillations is seen and we limit $|U_{\mu4}|^2$ to less than 0.041 and $|U_{\tau4}|^2$ to less than 0.18 for $Δm^2 > 0.8$ eV$^2$ at the 90% C.L. in a 3+1 framework. The approximations that can be made with atmospheric neutrinos allow these limits to be easily applied to 3+N models, and we provide our results in a generic format to allow comparisons with other sterile neutrino models.

hep-ex↗

arXiv2015

Test of Lorentz invariance with atmospheric neutrinos

A search for neutrino oscillations induced by Lorentz violation has been performed using 4,438 live-days of Super-Kamiokande atmospheric neutrino data. The Lorentz violation is included in addition to standard three-flavor oscillations using the non-perturbative Standard Model Extension (SME), allowing the use of the full range of neutrino path lengths, ranging from 15 to 12,800 km, and energies ranging from 100 MeV to more than 100 TeV in the search. No evidence of Lorentz violation was observed, so limits are set on the renormalizable isotropic SME coefficients in the $eμ$, $μτ$, and $eτ$ sectors, improving the existing limits by up to seven orders of magnitude and setting limits for the first time in the neutrino $μτ$ sector of the SME.

hep-ex↗

arXiv2014

Search for Trilepton Nucleon Decay via $p \rightarrow e^+ νν$ and $p \rightarrow μ^+ νν$ in the Super-Kamiokande Experiment

The trilepton nucleon decay modes $p \rightarrow e^+ νν$ and $p \rightarrow μ^+ νν$ violate $|Δ(B - L)|$ by two units. Using data from a 273.4 kiloton year exposure of Super-Kamiokande a search for these decays yields a fit consistent with no signal. Accordingly, lower limits on the partial lifetimes of $τ_{p \rightarrow e^+ νν} > 1.7 \times 10^{32}$ years and $τ_{p \rightarrow μ^+ νν} > 2.2 \times 10^{32}$ years at a $90 \% $ confidence level are obtained. These limits can constrain Grand Unified Theories which allow for such processes.

hep-ex↗