 Good afternoon, everybody. It's a privilege and honor to welcome Professor Takaki Kajita as our today's speaker in this lecture series, jointly organized with Ryukyu Shimpu. Kajita has spent his career addressing questions that are as old as the human race itself, such as those famously posed by the French painter Paul Gauguin. Where do we come from? What are we? Where are we going? Well, some of these questions can be addressed using scientific means. So where do we come from? The best supported CLV of the origin of our university centers on an event, as we all know, called the Big Ben. This theory was born of the observation that other galaxies are moving away from our own at great speed in all directions as if they had all been propelled by an ancient explosive force. It's thought that this acceleration is driven by a force that repels gravity called dark energy. We still don't know what dark energy is, but physicists think that it makes up 68% of the universe's total matter and energy. Dark matter makes up another 27%. In essence, all matter you have ever seen from your first love to the stars overhead makes up less than 5% of the universe. Discovering what components make up our universe is a crucial step towards an understanding where we come from. Takaki Kajita has delivered a major finding to address that question. Kajita was born in Higashi Matsuyama, Saitama, Japan. He studied physics at Saitama University and then the University of Tokyo where he received his PhD in 1986 working under the 2002 Nobel Laureate, Masatoshi Koshiba. Since 1988, Kajita has been affiliated with the Institute for Cosmic Ray Research at the University of Tokyo, rising to professor in 1999 and director in 2008. Kajita has received numerous awards for his work and in 2015, he was awarded the Nobel Prize in Physics jointly with the Canadian physicist Arto Macdonald for his work on neutrinos. We live in a world of neutrinos. There are billions in this room right now traveling almost at the speed of light. Neutrinos are the second most abundant particles in the universe after light carrying particles known as photons. They are created in nuclear reactions, for example in the sun and stars or in nuclear reactors. They interact very little with the environment and they drift through the earth and our bodies like wind through a screen door. There are three kinds of neutrinos, electron neutrinos, muon neutrinos and tau's neutrinos. Kajita and Macdonald won the Nobel Prize for their discovery that neutrinos can change identity. For example, a muon neutrino can become a tau neutrino and vice versa. They oscillate between different types. As the Nobel Prize committee stated, the discovery implies that neutrinos, which were believed to be massless, do have a mass even if very little and since there are so many of them, it changes our view of the universe. In a news conference at the University of Tokyo shortly after the Nobel announcement Kajita said, I want to thank the neutrinos of course and since the neutrinos are created by cosmic rays, I want to thank them too. Detecting neutrinos was considered almost impossible for a long time ever since 1930 when the Austrian physicist Wolfgang Pauli suggested their existence. He later joked that he has done a terrible thing. He said, I have postulated a particle that cannot be detected. Thank God he was wrong. Hence, revealing the neutron's identity and characteristics required an ingenious setup. That ingenious setup has a name, the super cameochande detector. The super cameochande is a neutrino observing facility located 1,000 meters underground in Hida City, Gifu Prefecture. And I'm sure you will tell us more about it and probably also shows on beautiful slides. Kajita's experiments with the super cameochande along with McDonald's experiments at the Sudbury Neutrino Observatory in Canada confirmed experimentally that neutrinos can change from one identity to another. Therefore, the discovery of neutrino oscillations became definitive proof that neutrinos have a mass that is not zero. The experiments rewrote the balance sheet of the universe and we now know that the collective weight of the neutrinos once thought to be massless is about equal to the collective weight of stars in the cosmos. But Professor Kajita dedicated his life not just doing his own scientific work. He has taken on greater responsibilities for science and society as a whole. In October this year, he became the president of the Science Council of Japan, enabling him to promote and enhance science in Japan and beyond. In this role, he publicly had to take a stand against Prime Minister Suga defending the independence and autonomy of science and science management decisions. After Prime Minister Suga decided not to appoint academics who have been critical of the nation's security and anti-conspiracy legislation to a science council, the chair of who is here, that makes policy recommendation to the government. We are very happy, Professor Kajita, to have you here and we are looking forward to a great talk. I think all of us give him a warm welcome. Thank you for coming. Thank you very much. I think, no? It must be okay, yeah. Okay. Well, it's my pleasure to give a talk here in OIST. So today, I'm going to talk about the universe with, well, exploring the universe with neutrinos and gravitational waves. Well, actually, this title is rather general, but well, I have to apologize maybe before starting. I'm going to talk about our work, maybe 80% of this talk, so I hope it's okay. Okay, well, this is the outline. First, I'm going to talk about the neutrinos studies in Kamioka. Then I want to move on to the gravitational waves. That is the rather, well, for us, it's a new project. The project name is called Kagura. So I'm going to talk about the gravitational waves and I'll summarize this talk. Okay, now, I want to begin from the Kamiokanda experiment. Well, in the 80s, large underground detectors were constructed to observe proton decays. In the 70s, grand unified theories predicted, grand unified theories of elementary particles predicted that protons should decay with the lifetime of about 10 to 30 years. Well, actually, 10 to 30 years seems to be, well, of course, long, but seems to be detectable. Therefore, several experiments were constructed and here, I show you two examples. One is the IMB experiment in United States. That was 8,000 ton water detector. And another example showing, right, is the Kamiokanda experiment. That was slightly smaller than IMB. That was only 3,000 tons. So from now on, I'm mostly going to talk about the Kamiokanda experiment. First of all, let me introduce the location of this experiment. Well, of course, this is the map of Japan. I'm sorry, Okinawa is not shown here, but anyway. Well, the location of the experiment is there. So you see where you expect the mountain area and you are right. So this is the photo of the Kamioka site. And if you look at the photo carefully, you can see some facilities in the mountain. That is the mining facility. So Kamiokanda was constructed in an active mine. And the mountain for the mining is shown in the right. And well, and I want to show you this photo. This photo was taken in the spring of 1983, where we constructed the Kamiokanda detector. And well, first of all, you can see a gentleman in front in the middle. That is Professor Koshiba. And he was my thesis advisor. And as I introduced, he received the Nobel Prize in Physics in 2002 based on his work in Kamiokanda. Anyway, so at the time, we are about to enter into the mine to construct the detector. And well, oh, by the way, I want to say behind Professor Koshiba, there are four young students. And they were the member of the Kamiokanda team. And of course, one of them was me. And these four members worked several months in underground to construct the Kamiokanda detector. Anyway, the construction was successful. And we started the experiment in July, 1983. And of course, we wanted to observe the proton decay. But as you may know, proton lifetime was much longer than initially expected. So we didn't observe any proton decay. But well, I think Professor Koshiba was great. After several months, we started observing proton decay but realizing that the Kamiokanda detector is very sensitive. Then he proposed to combat the proton decay experiment to a neutrino experiment, trying to observe neutrinos from the sun. And therefore, we came back to the mine in 1984 and started the work to modify the detector. And the work continued for several years. And we were able to start the stable operation in January, 1987. Now, I want to show you this slide. This is actually, sorry, this is written in Japanese, but I don't go into detail. This is actually the history of a star. If the mass is small, then it will have a very long life. If a star is the size like the our sun, then well, the life will be around, say. 10 billion years. If the star is heavier than our sun, say 10 times heavier, then the life should be much shorter and finally, at the end, it will explode. This was actually taken from a popular science magazine in the 80s. So this kind of story, this kind of star life was theoretically understood. But at the time, we didn't really confirmed this final stage is really true. Then in February, 1987, a supernova occurred a supernova occurred in large magnetic cloud that is the galaxy next to our Milky Way galaxy. This is a photo before the supernova explosion and you can see a star here, then this is after. So, a supernova happened and fortunately, as I said, at that time, we resumed the data taking in Kamiokande. So we look at the data and we found 11 neutrino events within 13 seconds. This is a summary of the supernova-neutrino observation by three experiments, Kamiokande, IMB and Baxan experiments. So in total, 24 neutrino events were observed observed by three detectors on this date. And with this, we understood the basic mechanism of the supernova explosion. And therefore, Professor Koshiba received the Nobel Prize in Physics in 2002. Okay, well, that was the story and with this, we confirmed this. Heavy star's life. However, I have to tell you, around that time, although we generally understood that at the end of the star's life, these heavy stars should explode. But around that time, essentially, no one was able to reproduce this process by simulation. However, because of the actual observation, people were more serious to reproduce the supernova explosion by simulation. But well, around that time, no one was successful. And only in recent days, people were able to reproduce the supernova explosion or I'm sorry, I cannot control. Well, okay. So this tells you how the heavy metals were produced by nuclear fusion processes in stars. Then at the end, iron is produced. Then normal fusion processes continues. Then because of the extreme pressure, this center core collapse. Well, of course, that kind of general picture was understood. The point was, well, if you look at the simulation carefully, you notice that the simulation does not assume sphericity. In fact, this kind of full 3D simulation was essential to really reproduce the supernova explosion. Anyway, I think we contributed to the simulation community to motivate them trying to reproduce the data. So that way, I think we contributed to their community. Anyway, okay, move on. Okay, that was one example. In addition, of course, we confirmed or we observed the solar neutrinos as we wanted. And also we confirmed with this, we confirmed the energy generation mechanism of the sun that is nuclear fusion processes. And also we confirmed the solar neutrino deficit. For this, I'll come back later. Furthermore, we observed neutrinos created by cosmic rays. These cosmic ray neutrinos were studied in Kamiokande because they were the background for the proton decay searches. Then unexpectedly, we find that there's a problem. We observed a deficit of atom-seq muon neutrinos. And that was the initial hint for the neutrinosilations, atom-seq neutrinosilations. So these are the brief summary of the Kamiokande experiment. And with this, I think we were able to convince the community that water-challenged of detector is very useful for neutrino physics and astrophysics. Therefore, the Japanese government approved the next generation neutrino detector that was super Kamiokande. Super Kamiokande is a bigger version of the initial Kamiokande detector. It is about 40 meters in diameter and 40 meters in height, containing 50,000 tons of very clean water. It is an international collaboration. We have about 190 collaborators from 10 countries. And the real detector looks like this. This photo was taken in January, 96, when we essentially finished the construction at the time. We are filling pure water. Very clean water into the super Kamiokande tank. And you can see the water level. You can identify the water level by recognizing a small plastic boat. So this is the detector to study neutrinos. And the experiment started in April, 96. Now I want to discuss the results from this experiment. As I briefly mentioned, neutrinos are created in the atmosphere of the earth. Cosmic particles interact with air nucleus and produce typically pions. And pions decay to muons, then to electrons. During this decay chain, neutrinos are created. And these neutrinos are studied in super Kamiokande. By the way, eventually it is about 10 neutrinos per day. So we have high statistics. And well, in fact, due to this high statistics, we were able to announce the first important result after two years of the data taking. That announcement was made in the Mutino Conference in June, 98. And here I show you the copy of the slide we showed at the conference. And well, of course, 98 was more than 20 years ago. And therefore the technology was completely different. Around that time, we didn't have PowerPoint. Instead, we had plastic seats. So around that time, we copied the data to the transparent plastic seats and wrote down several comments. Well, but of course, there is a reason that I show you this slide. This slide was so important. In particular, the lower one was very important. This is for muon neutrinos. And cosine theta means gene-sangle. One means down-going neutrinos. Minus one means upward-going neutrinos. Of course, these neutrinos came from the other side of the earth. And small black circles with error bars show the data and these hatched histograms show the Monte Carlo prediction. And you immediately notice for down-going neutrinos, the data and Monte Carlo simulation agreed quite well. However, for upward-going neutrinos, the data showed almost a fact of two deficit. And this can be very well understood if you take into account the neutrino oscillation. And therefore, of course, we carried out the oscillation analysis. And the analysis results are shown here. Using this data together with some other data, the oscillation parameter constraint is shown here. Oh, by the way, this is, well, so a bit technical. This is the mixing angle, sine square two theta, mixing angle of neutrinos versus the delta M square, neutrino mass square difference. Anyway, that is maybe two detail. Anyway, this is the fit result. A lot of reason was here. And we have another data samples. And all of these essentially suggested one parameter space. And all of these turned out to be just consistent. Therefore, Super Kamioka and we concluded that the observed Zins angle dependent deficit and the other supporting data gave evidence for neutrino oscillations. That was 98. Okay. Then, well, I think Super Kamioka was lucky because we had an accelerator facility that is KIK. And they had a proton synchrotron and they decided to produce a neutrino beam with the existing proton synchrotron. And with the baseline links between the proton synchrotron in KIK and Super Kamioka was 250 kilometers. And with this configuration, we confirmed the neutrino oscillation. Furthermore, we were even more lucky. KIK together with the, I think, JAA. But had a plan to construct a new accelerator called J-PAC. This is a very high-intensity proton machine. And it's this. They decided to produce very high-intensity neutrino beam directing to the direction of Super Kamiokande. And therefore, we were able to do the second-generation long-based line experiment. And with this, we were able to confirm the three-flavor oscillation effect. That means most of the muonutinos oscillate to tau-nutinos that was confirmed with this experiment. But with this experiment, we confirmed a small fraction of the muonutino changed to an electron-nutino. So I think Super Kamiokande together with these accelerators were very successful in studying the neutrino properties. Now, I want to briefly mention about the solar neutrino oscillations. Well, of course, the sun generates energy by nuclear fusion processes. And during these processes, many neutrinos are generated. Therefore, more than 50 years ago, some people thought that we should confirm the nuclear fusion processes in the sun by observing solar neutrinos. And this is the copy of the first solar neutrino experiment led by Ray Davis. And this was located in Homestake in the United States. And this Homestake solar neutrino experiment observed solar neutrinos for the first time, slightly more than a half-century ago. However, there was a problem. The event rate was only about one-third of the prediction. And there were subsequent solar neutrino experiments, but the problem was just confirmed by the subsequent experiments in the 80s and 90s. So this was called solar neutrino problem. Then, earlier in this century, this problem was understood to be due to solar neutrino oscillations. And the main experiment that understood the solar neutrino problem was the snow experiment. This was another challenge of the detector, but instead of normal water, they used heavy water. They used one-third of tons of heavy water. And in fact, this is a very expensive experiment. Heavy water is not so cheap. Anyway, using heavy water is extremely important. That is very important. Let me tell you why. With heavy water, of course, there are deuterons. Then, electron neutrinos interact with the deuteron producing E minus Pp. And this way, a snow experiment can measure the electron neutrino flux. Independently, neutrino can interact with a deuteron, this integrating this deuteron into proton plus neutron. And this is a neutral current. Therefore, this interaction does not depend on the neutrino type. Therefore, the event rate is simply proportional to the total neutrino flux. And the result is shown here. If they observe the electron neutrino flux, the event rate was about one-third of the prediction. However, if they observe the total neutrino flux, then the event rate was just as expected. That means two-third of the neutrinos are muonutino plus tau-neutrinos. And therefore, this way, people are convinced that the solar neutrino deficit was due to neutrino oscillations. And by the way, here is the super-camiocand data. And super-camiocand observe solar neutrinos by neutrino-electron scattering. And in this process, we mainly observe electron neutrinos, but we are also sensitive to muon plus tau-neutrinos with lower cross-section. Then they observed flux was this much, and in fact, this was just consistent with the SNOR result. So this way, we understood that the solar neutrino deficit was due to neutrino oscillations. Now, okay, so far, I have briefly, well, I have discussed our experimental work. And with these works, we observed, we found that neutrinos have small mass because neutrinos oscillate. Then you may ask, why the neutrino mass is so important? Well, of course, electrons have mass, quarks have mass. And in fact, this shows the mass of elementary particles. There are three charged leptons, three types of charged leptons. These mass are shown by these red colors. There are six types of quarks. These mass are shown by these blue and green colors. Now, after 20 years of intensive studies of neutrinos, we almost understand the neutrino mass value. And let me plot the neutrino mass. They are here. So, you notice that neutrinos are much smaller than the corresponding mass of charged leptons and quarks. And in particular, if you want to be a little bit more careful, well, if you read the figure a little bit more careful, you immediately notice that the neutrino mass approximately, or maybe more than, 10 orders of magnitude smaller than the corresponding mass of quarks and charged leptons. So, 10 orders of magnitude difference. So, neutrino mass are extremely small. And we believe that this is the key to better understand elementary particles in the universe. So, therefore, we are excited with the neutrino mass. And of course, if we understand why neutrino mass are so small compared with the other charged leptons with other particles mass, then we believe that we better understand elementary particles. But why the universe is relevant? Well, we think the neutrino mass is relevant to our better understanding of the universe. And let me explain why we think so. Well, this is a photo of the five universe taken from the net. And we see many stars and galaxies. And we know that all these stars and galaxies are made of matter. We know there are no antimatter galaxy, no antimatter star. This is a bit strange if we think about the Big Bang universe. In the Big Bang universe, the universe was extremely hot. Then in this extremely hot universe, always matter particles and antimatter particles are created simultaneously. So, in the Big Bang universe, the number of matter particles and antimatter particles should have been equal. Then with the universe cooled down, matter particles and antimatter particles meet and annihilate, disappear. Therefore, naively, we expect no matter in the present day universe. But of course, we observe matter in the universe. Why? Well, we have an answer. We know, we expect that in the Big Bang universe, there was say one billion, one matter particle. But the number of antimatter particles was one billion. They were almost equal. Then with the universe cooled down, matter particles and antimatter particles meet and annihilate. Then we have this one in the present day universe. So, this way we can explain. Of course, one billion, one is almost equal to one billion, but not exactly. Therefore, we have to explain why there was this extra one in the Big Bang universe. And in fact, we do not know why. But we think that neutrinos with very small mass might be the key to understand this extra one in the Big Bang universe. But well, actually, this is just a possibility. So, we have to confirm experimentally if this idea is correct. Therefore, in the neutrino community, there are big projects going on. One is in United States, one is in Japan. And we'd like to observe if oscillation of neutrinos and those of anti-neutrinos are different. If the difference is observed, it will be the first step to understand origin of the matter in the universe. Namely, we'd like to observe the difference in neutrinos and anti-neutrinos. This is called CP violation. And this is the sensitivity of these two experiments. Well, of course, these experiments are under construction. Therefore, we do not have any data. Therefore, this is the expectation, assuming 10 years of experiments with these projects, then this is the sensitivity or significance of the difference between oscillation of neutrinos and anti-neutrinos as a function of the CP phase delta. So first of all, this is for the U.S. Project Dune, and this is for the project located in Japan, Hyper-Kamiokande, and this is the significance of the statistical significance of the difference of neutrinos and anti-neutrinos. And therefore, depending on, of course, the statistical significance depends on the CP phase angle delta, but you see for a large fraction of the phase space, these experiments will observe the difference between neutrinosilations and anti-neutrinosilations. Well, of course, these are the expectations we have to construct the detector. And let me mention about the status of the experiment. Well, since I'm slightly involved in Hyper-K, Japanese project, so let me mention about the status of the Hyper-Kamiokande. So the detector itself will be like this. It will be about 70 meters in height and 70 meters in diameter. The fiduciary mass is about 10 times larger than the present Super-Kamiokande. So this is really going to be a huge detector. And because of this huge mass, we expect many important research in neutrinophysics and astrophysics. And the construction has just started in this year and the experiment will start hopefully in 2027. And this is an international collaboration. We have more than 400 members from 19 countries. Well, okay, maybe I spend too much time, but I want to move on to the gravitational waves. Well, I said that I'm slightly involved in this Hyper-Kamiokande. That means I'm mostly involved in something else. And that is gravitational waves. And slightly more than 10 years ago, I thought that I want to do something new. So I decided to change my research from neutrinos to gravitational waves. Well, okay, maybe I should, I, well, I don't know if I, okay, yeah, anyway. Say, suppose there are two black holes orbiting each other, then from this kind of system, we expect gravitational waves. So say this is the expected gravitational wave signal by emitting the gravitational waves. They come closer and orbiting faster. Come closer, closer. Of course, this is moving. So it's got slowed down and much. A new heavier black hole is formed. Then if you look at the outer space, you'll notice that the gravitational wave is propagating to the outer space. So we expect to observe these signals, but the question is how can we observe these signals? And, well, for this audience, I don't want to show the movie. We are going to use the laser interferometer. Then, well, you may remember, more than four and a half year ago, there was an announcement. This was the first observed signal of gravitational wave and this was the simulation. So the signal and simulation agreed quite well. Furthermore, there were two detectors and the signals from the two detectors agreed quite well. So is this the LIGO, scientific collaboration announced the discovery of gravitational wave? I said there are two detectors. They are located here and here in United States. And of course, you notice that these detectors are very large. Yes, we need very large laser interferometers to observe gravitational waves because the expected effect due to gravitational waves is extremely small. And actually, I want to tell you how small the expected effect is. Here, I show you the sun and the earth. The distance is 150 million kilometers. Then, if a big gravitational wave come, that can be detectable with the present generation detectors, then the distance between the sun and the earth changes. The question is, how much distance change do we expect? The answer is we expect 10 to minus eight centimeter over 150 million kilometers. So every gravitational wave detector has to be sensitive to this length change. Unfortunate thing is every laser interferometer we have on the earth have only three to four kilometer arm lengths. Therefore, these detectors must be sensitive to the length change of 10 to minus 16 centimeters in three to four kilometers. And in fact, if your arm length is longer, then you are more sensitive. Anyway, you have to target this number in three to four kilometers. Anyway, LIGO interferometer in United States and Virgo in Europe were able to come to this sensitivity. And they were able to observe many signals of the mergers of binary black holes. Here, the vertical axis shows the mass of these black holes in unit of the solar mass. So LIGO and Virgo collaborations observed many mergers of black holes with the typical mass of several tens of solar mass. Furthermore, they find an interesting event. These two stars mesh to a heavier one. In fact, these two are neutron stars. And well, in fact, this signal, well, this merger was rather close to the earth. Therefore, they had rather precise measurement of this event and they were able to have to decide that they were able to determine the direction of this event rather precisely. And then astronomers followed, well observed, a tractor observed the new star here, this one. And they found this one. Well, previously there was no bright star, but after the merger, they found this one. So because of the successful pointing of the binary neutron star merger, the optical community followed the observation. And then there were several optical observations. And in fact, with these follow-up observations, people realized, for example, heavy metals were created with this event. So now it's clear that we can do many important science with gravitational waves. And well, this is the science we can carry out with the present generation experiment. And we'd like to observe the merger of binary neutron stars and we want to understand the origin of the heavy metals in the universe. Of course, with the 2017 observation, we knew, already knew that heavy metals were created. Furthermore, we'd like to observe the merger of binary neutron, no, binary black holes. And in fact, these observations already told, tells us the new mystery. These black holes were rather heavy than we expected. So we'd like to understand how these black holes were created. Maybe these black holes were the initial hint for the first generation stars. Astronomers expect that the first generation stars should have been much heavier than the present generation stars. So with gravitational waves, we may be observing the evidence for the first generation stars. And finally, we'd like to observe supernova explosion with gravitational waves. And we'd like to understand better how the supernova explode. So we have a lot of science. Therefore, we'd like to study more on gravitational waves. And therefore, in Japan, we have been constructing the Kagura Interferometer. Well, although this is located in Japan, it's another international collaboration. We have about 400 members from 10 countries. So this is the sketch of the Kagura Interferometer. It is located again in Kamioka, in the mountain, underground. And in fact, we decided to construct the Interferometer in underground because in underground, and the seismic activities are much smaller. Typically, two orders of magnitude smaller. Therefore, that is an advantage for the gravitational wave interferometer. Furthermore, in Kagura, we are going to use cryogenic mirrors. As I said, we have to measure the length change of 10 to minus 16 centimeters over three kilometers. Therefore, the thermal effect is a problem to achieve 10 to minus 16 length change sensitivity. Therefore, we decided to cool down the mirrors. Anyway, the project was approved in 2010. Well, when project was approved, of course, we had no tunnel for the interferometer. Therefore, initially, we had to excavate the tunnel. Then after the completion of the excavation, we installed the three kilometer by three kilometer vacuum tubes. These are the photos of the three kilometer vacuum tubes. Well, this is big, 80 centimeters in diameter. Anyway, the connection and the leak test of three by three kilometer beam tubes have been finished in March, 2015. And after that, we begin to install the mirrors into the vacuum tanks. One of the mirrors looks like this. This is one of the cryogenic mirrors. It is 22 centimeter in diameter, 15 centimeter in thickness, and the weight is 23 kilograms. And well, actually, this is the preparation of the mirror at the University of Toyama. Then this mirror is moved to the Kamioka site. And in November, 2017, we installed the first cryogenic mirror into this huge cryostat. And this photo was taken at the time, and you notice that these many people contributed to install just one mirror into the cryostat. And well, of course, we have many other things to do, and now the experimental area looks like this. So everything is covered, every important part is covered by a cream booth. And so you cannot see the detail, but anyway, here is the beam spritter and beam spritter tank. And with this mirror, the beam is split into two. And also, well, of course, this is the inside the tunnel. But after the completion of the construction, we cannot access to the underground because the human activity is a noise to the gravitational wave observation. Therefore, after the completion of the construction, every work is remote work, remote work where we have outside office, outside of the mine, and then people, young people, in particular young people, are working hard to control the interferometer from this office building. And I want to show you the brief history of the Kagawa sensitivity improvement. We finished the installation of the interferometer in the spring of 2019, last year, so after nine years of work. Then in August last year, we were able to operate the interferometer. That means we were able to observe the interference light and the sensitivity at the time is shown this green curve. Then we had several improvement until March this year. So at the March this year, we achieved this level. And this is the design sensitivity. So unfortunately, we are still not so close to the design sensitivity. But, well, certainly we improved. For example, if we look at the USA's 300 Hertz range, then within this, how many months? So actually more than half a year, we improved the sensitivity by four dozen magnitude. So at the time, we started the operation. Then due to COVID-19, no one was able to come to the site. And the number of people in the site was so limited, we stopped the operation, 24 hour operation a day, in two weeks, so that is the status. Since then, we are stopping the operation. And well, of course, the same is happening in other projects, U.S. and Europe. All these are stopping the operation. And therefore, we have been discussing with our U.S. and European colleagues what we should do next. And essentially, we have been deciding that we'll have the joint observation in 2022. We do not know the months, but 2022 is the target. So we'll join the observation. And we hope that at that time, we further improve the sensitivity and we achieve the reason of a good sensitivity. By the way, I think I didn't mention why we are going to have the joint observation with these interferometers. Well, we believe that the scientific output will be maximized by the global network. For example, a very important information from the global gravitational wave network is the directional information. From any single interferometer, we have no information about the arrival direction of the gravitational wave. If you have multiple interferometers, then by observing the time difference of the arrived signal, you can estimate the arrival direction of the gravitational waves. But if the detectors are only in United States and Europe, then the accuracy could be something like that. So depending on the source, so in some cases already with this configuration, the accuracy of the arrival direction determination is good, but in some cases, the arrival direction is poor. But if we include Kagura, then Kagura is far from these two other detectors, then we can substantially improve the determination of the arrival direction. And that way, we'd like to contribute to the gravitational wave astronomy. And finally, so far I separately discussed neutrino physics and gravitational waves, but we are not completely independent. Say, suppose a supernova explodes at the center of the Milky Way, for example, then we should observe a lot of neutrino events in these neutrino detectors. In addition, we should have important data from gravitational waves. And by combining these two data, we truly understand the mechanism of the supernova explosion. And of course, the other information such as optical observation or simulations are very important. Okay, so that way, neutrino and gravitational waves are not independent. Okay, basically that all, neutrinos and gravitational waves are new eyes and ears to study the universe. That's all, thank you very much for your attention.