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 HayatoProfessor

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.

Atsushi Takeda(Associate Professor)

Specialized Fields

Experimental particle physics, neutrino observation, dark matter search

Content of research

My research focuses on neutrinos from celestial bodies including the Sun, and on dark matter.

With regard to neutrinos, I aim to detect those originating from supernova explosions, which occur at the end of the lives of massive stars, using Super-Kamiokande (SK) and Hyper-Kamiokande (HK) currently under construction. SK and HK are expected to achieve large statistic detections, particularly by utilizing events in which anti-electron neutrinos interact with protons in the detector. Since SK was upgraded to SK-Gd, the accuracy of arrival direction has been greatly improved by extracting events in which neutrinos scatter electrons. Furthermore, dark matter detectors using liquid xenon, which are sensitive to all types of neutrinos, are expected to obtain information complementary to that of SK and HK by using coherent elastic scattering with atomic nuclei.

Dark matter is an unknown substance that has been revealed through various astronomical observations to exist in an amount more than five times greater than the “normal matter” that makes up the things around us. We are conducting research to directly search for dark matter using a liquid xenon detector called XENONnT in Italy.

To the students

In particle physics experiments, creating and developing excellent detectors is a very important activity. I think it would be a very exciting and valuable experience to be able to use a detector that you have been involved in to discover phenomena that no one has ever seen before and contribute to advancing humanity’s understanding of the universe. The Kamioka facility is well-equipped to provide such an experience, so if you are even slightly interested, please contact us.

Yoichi Asaoka(Associate Professor)

Specialized Fields

Experimental astroparticle physics: Direct cosmic ray observation, Hyper-Kamiokande

Content of research

As a fourth-year undergraduate student, I aspired to conduct particle physics experiments using the highest-energy accelerators. However, upon joining a research lab, I became involved in the BESS balloon experiment, which explores “particle phenomena in the universe.” Following that, I participated in the CALET experiment, which directly observes high-energy cosmic rays aboard the International Space Station. Over the past 30 years, direct cosmic ray measurements have evolved into precision experiments, and the achievements of BESS and CALET have made significant contributions to this progress.

Through these experiences, I have come to deeply appreciate the importance of “direct” measurement in obtaining experimentally reliable results. At the same time, I feel that the potential for particle physics discoveries through high-precision cosmic ray observations has diminished. To pursue discoveries in particle physics, I believe that directly measuring “particle phenomena” is the best approach. With this in mind, I joined the Hyper-Kamiokande experiment in 2020. Currently, I am leading the construction site of Hyper-Kamiokande, aiming to begin the experiment.

The Hyper-Kamiokande project offers an exceptional opportunity to directly measure the constants embedded in particle physics. If the symmetry between neutrinos and antineutrinos is broken to the greatest extent possible, it may imply that this asymmetry played a crucial role as a necessary condition for the existence of observers like us in the present universe. I am excited about the discoveries that Hyper-Kamiokande may bring and the future developments in particle physics that will follow.

To the students

Starting in the latter half of fiscal year 2026, Hyper-Kamiokande will enter a critical phase: the construction of the PMT support structure and the installation of photomultiplier tubes and electronics modules. Researchers from around the world will gather not only to install the detector itself, but also to carry out parallel tasks such as assembling and calibrating individual components, cabling, and conducting operational tests. Are you interested in meticulous planning, optimization, and management to make the most of the researchers’ manpower? Contributing to and gaining experience at the heart of detector construction in Hyper-Kamiokande is a rare opportunity that can only be found here in Kamioka right now. If this sounds exciting to you, please don’t hesitate to reach out. Let’s complete the construction of Hyper-Kamiokande together and be part of its first groundbreaking discoveries.