Super-Kamiokande (SK) is the 50 kton water Cherenkov detector located at Kamioka mine in Japan. In 2020, we dissolved gadolinium sulfate in the SK water and started SK-Gd phase with 0.01% Gd, where neutron detection efficiency and resolution for neutron capture vertex are improved. Detection efficiency got even higher at the second Gd loading to 0.03% Gd in June 2022. In atmospheric neutrino...
A half-wave plate (HWP) is often used as a modulator to suppress systematic error in cosmic microwave background (CMB) polarization measurements. An HWP can also be used to measure circular polarization through its optical leakage from circular to linear polarization. The circular polarization of the CMB is predicted to be produced by interactions in the Universe, such as interactions with...
Simons Observatory (SO) is the largest ground-based CMB experiment in history. SO is developing Small Aperture Telescopes (SATs) to detect the primordial B-mode signal. The cryogenic half-wave plate (CHWP) is an optical device for SAT which decreases systematic errors in the polarimetry. CHWP modulates polarized signals separating from unpolarized signals; the polarization modulation reduces...
The T2K experiment showed the strongest constraint on the CP violation phase in the lepton sector using neutrino oscillation and is seeking further improvement of the measurement sensitivity. To reduce systematic uncertainties, upgrades of the near detector are ongoing. In 2023, a new type of detector, called SuperFGD, is planned to be installed. SuperFGD is a high granular scintillator...
Hyper-Kamiokande starts its operation in 2027, and we are in the final stage of the development of the electronics. The large scale and high precision of the Hyper-Kamiokande require high performance and reliability on the electronics. We have developed frontend electronics such as digitizer, communication module and HV/LV module. And we plan to deploy the frontend electronics in water-tight...
Liquid scintillator (LS) detectors, composed of LS and photosensors, such as photomultiplier tubes (PMTs), have been widely used in neutrino experiments. Precise calibration of energy response (energy nonlinearity and energy resolution) for different particles in LS detectors is crucial for spectral analysis. For LS detectors used in reactor neutrino experiments, $e^+$ from the inverse beta...
We have upgraded the Super-Kamiokande in 2020 with Gd to enhance neutron tagging for anti- or normal-neutrino distinction. This neutron tagging method requires a special trigger and is limited to the higher energy of neutrino than around 8 MeV due to the energy of a 2.2 MeV gamma ray via hydrogen capture in the pure water phase. After the upgrade of doping Gd, this requirement is relaxed in...
We measured $^9\mathrm{Li}$ isotopic nuclei produced by muon spallation using the data taken from 2020 to 2022 by the Super-Kamiokande detector with 0.011% gadolinium concentration in water. $^9\mathrm{Li}$ is a long-lived radioactive isotope with a lifetime of about 0.26 seconds. It emits an electron and a neutron at a branching ratio of 50.8%, which is difficult to distinguish from the...
T2K is a long baseline neutrino oscillation experiment and search for CP violation in leptons using neutrino oscillation.For improving the result, it is very important to consider about the neutrino flux in Super Kamiokande (SK). Neutrino flux estimation is using neutrino beam simulation and one of the largest effects of the flux uncertainty is the cooling water for the magnetic horn : the...
Observing the degree-scale polarization pattern called “B-mode” in the cosmic microwave background radiation (CMB) map is expected to be proof of primordial gravitational wave and a key to revealing the inflationary universe. Recently, CMB polarization observation experiments with higher experimental sensitivities are in progress or planned.
For such precise CMB polarization observations, it...
Polarization of cosmic microwave background (CMB) is the best probe for primordial gravitational waves. In Simons Observatory, using the Sparse Wire Grid Calibrator, we can evaluate/reduce optical systematic errors on Small Aperture Telescopes (SATs). In this poster presentation, we will introduce an initial analysis for the optical performance of the calibrator
The cosmic microwave background (CMB) has a variety of information that is useful for understanding the early universe. The Simons Array, an ongoing ground-based CMB experiment, is located in the Atacama plateau in northern Chile. Its second telescope receiver has been installed and is being prepared at the site, including the set-up of the ambient temperature equipment and readout testing,...
We report the recent lattice QCD result of proton decay matrix element, which is QCD contribution to baryon number violating process, with PACS collaboration. We compute 12 relevant matrix elements on the physical point in lattice QCD, and this regards a more reliable value compared with the previous one computed from chiral extrapolation. In this poster, we show the systematic study to...
Close White Dwarf Binary systems in Miky Way Galaxy are important in two major fields of astrophysics. 1) Potential source of background gravitational wave and 2) Potential progenitors of Type Ia supernovae.
1) Potential Source of Gravitational Wave Background
Although the individual contribution is small, integrating numerous white dwarf systems may contribute to a gravitational wave...
Hyper-Kamiokande is a next generation water Cherenkov detector which has a fiducial volume of approximately 10 times larger than that of the on-going Super-Kamiokande detector.
In a deep water tank one of critical issue is prevention of chain implosion of large photosensors.
If a glass bulb crashes under high pressure in deep water a rapid cracking run over the whole glass in very short...
There is a positive correlation between the mass of SMBHs ($M_{\rm BH}$) and the stellar mass of their host galaxies ($M_{\rm star}$) in the local Universe, suggesting that SMBHs and galaxies have co-evolved. Studying distant galaxies is vital to understand the co-evolution process. Although it is difficult to measure $M_{\rm BH}$ in distant galaxies except for quasars, its time derivative,...
Gamma-Ray Bursts (GRBs) are very energetic cosmological transients. Long GRBs are usually associated with Type Ib/c Supernovae (SNe), and we refer to them as GRB-SNe. Since the associated SN for a given GRB is observed only at low redshift, a possible selection effect exists when we consider intrinsically faint sources which cannot be observed at high redshift. Thus, it is important to explore...
