Kamioka ObservatoryICRR, The University of Tokyo

Masato ShiozawaProfessor

Shigetaka MoriyamaProfessor

Specialized Fields

Astroparticle physics: neutrinos, direct detection of dark matter, proton decay, searches for new particles such as axions and undiscovered phenomena in particle physics

Content of research

We learned that the matter around us consists of atoms and molecules. However, when we look at the universe, it is not correct. Astronomical observations have revealed that most of the matter filling the universe is an unknown substance called dark matter. The issue in front of us is the nature of this dark matter. Understanding its nature opens the door to physics beyond the standard model. Therefore, our laboratory is working to directly detect dark matter by looking for interaction between dark matter and our experimental devices. Specifically, we are participating in an international research group, the XENON group, conducting experiments in Italy to detect dark matter with the world’s highest sensitivity.

Neutrino and proton decay research is also a major research topic in our laboratory. Based on our experience at Super-Kamiokande, we are currently constructing Hyper-Kamiokande, which is ten times as large as Super-Kamiokande. By observing nature with Hyper-Kamiokande, we want to get closer to the answers to fundamental questions such as why matter exists in the universe and whether matter decays out over a long time. We are preparing it by participating in Super-Kamiokande, which is currently running.

To the students

If you are interested in the direct detection of dark matter, we invite you to join us in our research on dark matter. It mainly involves data analysis to find evidence of dark matter in observational data by collaborating with researchers from many countries. We plan to conduct data taking about five years from 2021 in Italy. We will also guide and support your research to find signals that everyone may have missed by thoroughly understanding Super-Kamiokande in Kamioka, Japan. We can work to maximize its performance to study neutrinos, proton decay, etc. Please feel free to contact me if you have any interest in it. Online chat and actual visits are welcome.

Yoshinari HayatoAssociate Professor

Specialized Fields

Neutrino experiments (Neutrino-nucleus interactions, Neutrino oscillations)
Proton decay search experiments

Content of research

• I am conducting research to understand the nature of neutrinos mainly using the experiments on atmospheric neutrinos and neutrinos produced by accelerators in the Super-Kamiokande (SK) and T2K experiments. This research is conducted by observing particles produced by the reaction of a neutrino with a nucleon in a nucleus or with a hydrogen atom. Specifically, the research is conducted by comparing observation results (data) on the interaction caused by neutrinos with the simulation results. In addition, I am conducting research to correctly understand the interaction between a neutrino and a nucleus (experiments using T2K, Ninja, WAGASCI, etc.), which is the major premise for the above-mentioned research. Furthermore, I am developing simulation programs (NEUT) used in these experiments.
• Although protons have a large mass, their decay has never been observed. On the other hand, the “Grand Unified Theory” predicts the possibility of proton decay. In order to experimentally verify the mystery of elementary particles and the Grand Unified Theory, we are searching for evidence of proton decay.
• In order to collect data in these experiments, two systems are essential. One is electronics to digitalize signals from sensors, and the other is a data collection system to record the digitalized data. To contribute to these technologies, I am now developing systems for experiments at the Hyper-Kamiokande (HK) and also upgrading systems for SK experiments.

To the students

At present, gadolinium has been introduced in the SK, so the sensitivity for neutron detection has been improved. Thereby, it has become possible to conduct new analyses that are different from conventional ones. Now, data analyses that make the most of new information in neutrino oscillation and proton decay search are about to begin. In order to utilize new information, it is necessary to further deepen our understanding of neutrinos and nuclear scattering.
The preparation of the HK experiments is also steadily proceeding. Furthermore, the development of electronics to maximize the performance of detectors is now underway.
Students enrolling from now will be involved in the leading-edge research and development in each theme mentioned so far.

Hiroyuki SekiyaAssociate Professor

Specialized Fields

Cosmic neutrino observations, dark matter searches, astroparticle experiments, and detector developments

Content of research

The universe is filled with neutrinos and dark matter, and they are thought to have played a decisive role from the beginning of the universe to the present and future. We do experimental research on these elementary cosmic particles to elucidate the origin and mechanism of the universe.

Specifically, by improving Super-Kamiokande’s capabilities and understanding its properties as a detector, we are conducting research on neutrinos coming from the sun and searching for neutrinos from supernova explosions and various dark matter candidates.

In particular, we aim to first detect neutrinos emitted from past supernova explosions stored in the universe using Super-Kamiokande (SK-Gd), which has been upgraded to distinguish electron neutrinos from antielectron neutrinos by adding gadolinium (Gd). This leads to an understanding of how the elements that comprise our bodies were born. We are also conducting developments to realize Hyper-Kamiokande and detect dark matter and cosmic (background) neutrinos. We value research (discovery, observation, analysis, etc.) using our own (built, improved, calibrated, etc.) detectors.

To the students

It is essential to obtain new data and results to conduct experimental research. Regardless of the scale of the experiment, we are always required to do two things: to make the best use of existing detectors and to create noble detectors that no one ever has. Kamioka is a perfect environment when preparing for that, and you must enjoy the environment with your colleagues.

Please feel free to contact me if you are interested. I would help you find exciting projects and learn to conduct the research on your own.

Shoei Nakayama(Associate Professor)

Specialized Fields

Particle physics experiments, Astroparticle physics experiments

Content of research

To resolve the great mystery of why our universe consists of only matter (not anti-matter) and how our universe evolved, I conduct neutrino research using the Super-Kamiokande experiment. My subject to observe and measure are artificial neutrino beams made by the J-PARC accelerator and natural neutrinos generated by the earth’s atmosphere or astronomical phenomena. On the Hyper-Kamiokande experiment, which just began the construction to promote the neutrino research further, I’m leading the group to prepare the world’s largest underground cavity and a 260,000-ton detector water tank.

To the students

The SK-Gd project, which challenges new physics by adding gadolinium in the water of Super-Kamiokande, has finally started. It is good timing to try research that will lead to significant discoveries, such as improving the detection sensitivity of the neutrino CPV (matter-antimatter asymmetry) using the SK-Gd with the T2K neutrino beam or reducing the background of supernova relic neutrinos. In addition, on the Hyper-Kamiokande, you can enjoy a golden opportunity to make the world’s largest detector better with your own ideas and development. I hope to work together with you to create an environment where we can enjoy the rewarding research.

Masayuki NakahataProfessor

Specialized Fields

Supernova neutrino observations, Solar neutrino observations

Content of research

A star that is eight times heavier or more than the sun causes a big explosion called a “supernova explosion” at the end of its life. If a supernova explosion does happen in our galaxy, a huge number of neutrinos will be detected in the Super-Kamiokande (SK). Although such a supernova explosion is a rare phenomenon that happens once in 30-50 years, numerous kinds of data can be obtained if it happens. Thereby, we can investigate the mechanism of the explosion. On the other hand, it can be said that such supernova explosions have happened everywhere in space since the beginning of the universe. Therefore, such neutrinos (called “supernova relic neutrino”) are always flying around us. The frequency that a supernova relic neutrino interacts in the SK is about several times a year. Nevertheless, if we continue the observation for many years, an interaction of a supernova relic neutrino in the SK may be observed for the first time in the world. My main research is to investigate neutrinos from such supernovas.

To the students

You may think that Kamioka is far away. But there, world-leading research on neutrino and space/ elementary particles is being conducted. Students also spend their lives actively researching every day. “Neutrino” is considered to be a key to newly developing the fields of elementary particle physics and astrophysics. We expect that new students will participate in our research.