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This transcript is based on a tape-recorded interview deposited at the Center for History of Physics of the American Institute of Physics. The AIP's interviews have generally been transcribed from tape, edited by the interviewer for clarity, and then further edited by the interviewee. If this interview is important to you, you should consult earlier versions of the transcript or listen to the original tape. For many interviews, the AIP retains substantial files with further information about the interviewee and the interview itself. Please contact us for information about accessing these materials.
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In footnotes or endnotes please cite AIP interviews like this:
Interview of Yoichiro Suzuki by David DeVorkin on 1997 August 29, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/23109
For multiple citations, "AIP" is the preferred abbreviation for the location.
This interview is part of a small program to document the recent history of the American Astronomical Society. These interviews were used as background studies to help authors of chapters for the centennial history volume of the Society research and organize documentary materials. The volume was published in 1999. Some topics include: Brookhaven National Laboratory, Gran Sassa Laboratory, Osaka University, University of Tokyo. Prominently mentioned are John Bahcall, Masatoshi Koshiba, Alfred Mann, Kozo Miyake, Yorikio Nagashima.
Would you please state your full name.
Okay. My last name is Suzuki, and my first name is Yoichiro.
Tell me a little bit about your background. What kind of family you came from, what your father's name was, what his occupation was, and how you got into school, and what your goals were as child?
My father's name is Kenjiro Suzuki. He was born in Kobe. He's a tailor, and makes all the clothes.
Do you have brothers and sisters?
Yes. I have two elder sisters.
And did they go to college as well as you?
Yes, they went to private university.
A private university in Tokyo. You like to get the name of it?
Yes, I'm curious.
The eldest sister went to the Seishin University, and the second one went to the Waseda University.
Do they both have professions? Do they work?
I don't think so. One of my sisters studied English literature and English culture, but she married. The second sister learned French culture.
Is your generation the first in your family to go to college?
I don't think so.
Did your father have an education? Was he educated?
He didn't go to the university. He studied after high school and obtained a job. I don't know what he did once he married — many things, I think.
When did you first get interested in science?
Well, there were a bunch of books related to the sciences which I read when I was of junior high school or high school age, and I was very much interested in the relativity of quantum mechanics, those things, you know. Not really the real science, but science explained to make children understand very well. And I forget the names of the books, but you can buy them off the shelf from the book store.
How old were you?
Oh, I am very old now.
No, no, when you read the books.
Well, I don't know, 14, 15, or 16 years.
Did you have any teachers? Or did you go to public school or private school?
In Japan most people of that age go to the public school. There are very few people who go to private school. I of course went to the public school.
And which city was this in?
I was born in Tokyo, and I grew up in Tokyo, I went to school in Tokyo.
You had to take competitive exams? Did you go to the University of Tokyo?
No. I went to the University of Kyoto. At that time, there were problems at the university. Students were fighting the government. The University of Tokyo was momentarily closed, and an entrance exam was not available in 1969.
So you couldn't take the entrance exam.
No. So the university didn't have any new students that year. The trouble arose because of the security agreement between the U.S. and Japan for security and defense.
Right. It was a mutual defense agreement.
A Mutual defense agreement. It was originally signed in 1960, and was to be renewed every ten years. In 1970 it was time to renew or revise. Many of the students in the university were against the agreement and opposed the government. There was much turmoil. As a result, the government stopped the University of Tokyo from getting any new students.
Closed down. And so, I went to Kyoto University.
Did you enter physics?
Yes, I chose physics.
Right. But you were already interested in science.
Yes, I was already interested in science, inspired by the books I'd read.
Were they basically popular books.
Can you describe why you were fascinated with physics.
That's a very difficult question for me to answer now — I have to remember when I was very young. Usually we are sort of living in the many things which we really don't know, but by the method science we can reveal those secrets, find them out. I think that attracted me at that age.
Okay. Finding out about nature.
Yes, finding out the nature and the secret of nature.
Who were your professors at Kyoto, and how did you begin to specialize? Did you go in as a physics major?
Well, I think we are specialized at the graduate school. As an undergraduate, we are not specialized; we are sort of generally educated. So I went to the graduate school of Kyoto University, and took the high-energy physics laboratory.
Who were your teachers?
Professor Kozo Miyake.
Okay. Why high-energy physics? What was it about high-energy physics?
In my opinion, this is the most basic physics for everything. For once you understand high-energy physics you have resolved the problem of the particles and the forces between them. Everything is based on that. If you think of nature carefully and deeply, it brings you to the level of particle physics and the basic building blocks. I think this is the most interesting thing for me to study.
Okay. What did your father think about your going into physics?
What do you mean?
Did he approve of your going into science, or would he have preferred that you do something else?
My father didn't guide me or didn't tell me what I should do. He just simply said "You can do whatever you want."
Okay. So it wasn't as if he wanted you to follow in his tradition or anything like that.
No, I don't think so.
Could you describe the way that teaching took place at Kyoto? Did you have what you would call in the United States regular lectures and then laboratories and recitation?
Yes, we attended classes. I don't actually remember how often, and, of course, we had laboratory courses. At the university of Tokyo, the students took their classes and laboratory courses very seriously. But at Kyoto University the students pretended that they were not interested in classes. They study by themselves. They probably do not attend classes and laboratories very often.
Why do you think that's that way in Kyoto?
Kyoto has a kind of tradition. Tokyo and Kyoto represent two different systems. The university of Kyoto is a kind of system which educates the student to become a scientist. The purpose of the University of Tokyo is to turn out government officials.
Oh, government officials.
Kyoto is contrary to the University of Tokyo. They are kind of the style against the government. The University of Tokyo professor teaches students very well and educates, but the Kyoto University professor doesn't teach. Students learn by themselves. That's a difference between Kyoto and Tokyo. Kyoto has a different style.
And did you partake of this style?
Yes, I like the Kyoto style. We organized small groups to run studies, to learn using a textbook, and to learn physics by ourselves.
The students learn themselves.
Yes. So we sometimes can skip classes.
Did your professor, Miyake, appreciate this, or he played along with it?
Well, I don't know. He was a very quiet gentleman. I don't know how he felt about those things. Also, the time when I was in school, as I said, the oldest students were fighting the government. The university was in chaos.
In Kyoto and all other universities in a similar situation. So in that sense we were not really well educated by the professor.
I see. You are self-educated.
I see. Yes. But would you classify Professor Miyake as your primary professor?
Yes, of course, because he first guided us in the direction of high-energy physics and told us what high-energy physics is.
Now let's talk about the difference between observation or experimental work and theoretical work. Which kind of work interested you the most when you were a student?
Well, I liked both. Even though we have a very beautiful theory, theory itself doesn't make any sense unless it is proved by nature. So experiment is very essential. I think I like doing both experiment and theory.
In the case of theory, you can get together with your student colleagues and ignore the teacher and ignore the university and learn from books, but in the case of experiment you need the university.
So how did you gain access to experimental facilities?
Well, my Ph.D. thesis is based on the analysis of the data took by using the proton accelerator at Tsukuba, which was newly built at that time, in the early 1970s. Suzuki Tsukuba. They have a proton accelerator of 12 GeV. At that time they had the highest energy in Japan. Of course that was about 10 years or 15 years behind.
Behind what others had achieved.
Yes, okay. But did you perform your own experiment?
No, in a group. High-energy physics, even 20 years ago, still required a lot of money, and manpower, or a group, to make the experiment go. Professor Miyake was a leader in organizing such a group. Since I was a student, I joined his group. We worked together at the KEK. We call it KEK, this accelerator facility at Tsukuba.
I thought KEK had something to do with Kamiokande?
No. What is interesting is we plan to use a neutrino beam from KEK to detect the neutrino flux here at the super-K.
I heard about that.
Well, we shouldn't jump ahead, but I'd like to talk about that.
Okay. Yes. We can discuss that. Anyway, my Ph.D. thesis is based on the first experiment at KEK.
And that was on what?
We used a pion beam to bombard the protons — this makes a pi nought and the nucleons — to study the nucleon resonance. This was in the early seventies, or maybe the late seventies, '76 or so, just before the discovery of the charmed particles, so that current particle physics is, say, based on quarks and leptons as building blocks. But before that, you know, when I was writing this thesis, doing the experiment, we did not recognize this. Of course we had an idea of the quarks and leptons, but we did not know that beautiful symmetry of those quarks and leptons before we discovered the charmed particles. Then what we were doing was to study the resonance made by the excited nucleons by using the pion beam. That was a study of the excitation and fraction of the known quarks: u quarks and d quarks.
Did you say non-quarks?
No. So that was the kind of thing we studied, and then I analyzed the higher level excitation of the nucleons in my thesis. That's it.
Okay. Now I understand. So you basically had an experimental thesis that you then used, that you then interpreted using theory. And the theory changed as you developed it?
I don't think the theory changed. We added new information of the resonant state.
But you did your work before the charmed particles were known, or at least that new framework was developed. Now when did you graduate with a Ph.D.?
Excuse me, I have to count.
That's okay. Do you think in terms of the year of the emperor in your years?
Well, I use both, but you know sometimes I have to calculate. I'm sorry. I am now getting old and have a poor memory. [laughs]
No, no. I know a lot of people do that. It's very charming to me. Okay. Now, as you were nearing completion of your Ph.D., what is the normal procedure for the future? What were your plans for the future. Give me an idea of how it's normally done in Japan, and if you followed what you might call a normal course, a professional course, or was yours unusual in any way.
Well, at that time many graduate students, after earning their Ph.D., remained in university. They are called over-doctors. They do not have jobs.
That's sort of like a post-doctoral?
Even post-docs had a very hard time to find jobs. That's why good students are going to graduate school; it's since improved. Fortunately, in 1978 when I took my Ph.D., an agreement was signed between the U.S. and Japan on basic science. That program had just started. There were several projects in each laboratory in the U.S. — Brookhaven, Fermilab, and Berkeley. I was asked to join the Brookhaven experiment on neutrino physics.
Who was that in Brookhaven.
In Brookhaven? Hywel White and Al Mann.
Oh, okay. I don't know White. But he was leading the neutrino experiment at Brookhaven.
Also Alfred Mann; Pennsylvania was working with him closely. I think he was the actual spokesman.
So then did you go to Brookhaven in about 19 —?
And you came to know Alfred Mann then at that time?
Yes. I had been working for many years with him — he knows me very well, and I know him very well. But at that time I got a job at Brown University as a post-doc.
At Brown. Oh. And who were you working with then?
Bob Lanou. It's a French name. Lanou [pronounced la-noo']. Hard to pronounce.
Okay, Bob Lanou. Let's stay with Brookhaven first. What were your responsibilities in the neutrino experiment?
Well, at that time we were building the detector, which was based on liquid scintillators and proportional counters.
The purpose of the experiment was to measure the neutrino and electron scattering to make a precise measurement of sin2?w, weak mixing angle, which was not measured by the pure leptonic processes.
Leptonic. Okay, yes. I'm not a specialist in particle physics, so I need help in English as well. Pure leptonic. Okay. And was your work primarily experimental there?
Yes. I had the responsibility to make the liquid scintillator calorimeter.
You know, but the interesting thing is that I think that changes all my life, because the primary the goal of our experiment at Brookhaven was to measure the neutrino-electron scattering. However, in the early eighties there were many experiments related to neutrino mass. One was made by Fred Reines using the reactor experiment indicating the neutrino oscillation. It turned out to be wrong, you know, that experiment was a mistake. At the same time the experiment to measure the end point of the beta decay spectrum in Russia, giving an indication of 40 electron volts for the neutrino mass, was also wrong. Motivated by these experiments, I analyzed our data in terms of neutrino oscillations — so we can use the same dataset taken for studying neutrino-electron scattering. I also analyzed the data to search for the neutrino oscillation.
I know that that was a major question in physics, the oscillation characteristics. Okay.
I did that in the early seventies.
At Brookhaven. Of course that sets a limit, but the limit has lasted as a world record for five or six years after that. The paper on the oscillation was written by me.
And it appeared in the Physical Review?
It's a Physical Review publication.
Yes. If you have a copy of your Vita, your Curriculum Vita, I'd like to have it for the record. That would be very helpful.
I don't know that I have that here, because I moved my office from Tanashi, and brought only a very small fraction of my stuff.
So most of your stuff is in —
Yes, I can write it out, but —
Or send it to me back in the United States would be fine.
Now, you said that this really was a change for you at Brookhaven. Was it also a change in the way that you saw physics being done at Brookhaven? Was the physics being done the same way as it was being done at Kyoto or differently?
Oh, very differently.
Yes. Explain how.
Many of the physicists working in Brookhaven are sort of independent, they discuss every day and argue every day. I also like to argue with people. I was very aggressive, and I was young. But in Kyoto the style is very Japanese, well organized and under the control of the of the professor. I learned a lot of things to make the experiment successful. I think that it is very important for me learn different styles. Finally, I think it is good to deal with our foreign collaborators.
Your foreign collaborators.
I doubt if we can cooperate with our U.S. collaborators without this experience.
And that's because you have to know the way they operate?
I now know how they react. So you know, in this sense we can compromise. Otherwise we are sort of fighting and split and so we cannot compromise.
That's particularly important with an experiment like this which is very collaborative. Yes. When you met people like Hywel White and Alfred Mann and people like that, did you find that they pursued physics differently than Kozo Miyake, or did they think about physics differently?
Most of the Japanese professors will not do physics above certain ages, because that depends on the different systems of society between the U.S. and Japan. Many of them have to do very many other things besides physics, committee work, etc.. But Professor Miyake is rather exceptional. He at least tried to do physics after becoming a very important person at the university. U.S. professors continue to work on Physics regardless of age.
In the United States the interaction of observation and theory, did you find that to be any different there than here?
I think in Japan the situation is much worse. The theorists have their own way, don't listen to what the experimenters say. The experimenters also go their own way. So there is very quite little interaction between theorist and experimenter. [phone rings]
Okay. You were saying that theorists and experimentalists are very separate here. More than in the United States?
I think yes. In particle physics, we have a tradition of good work in the theories of Yukawa and Tomonaga, and also the experiments of high-energy physics. Experimental particle physics didn't happen in Japan until 1970 when the KEK, the national laboratory for high-energy physics, was set up. So particle physics in Japan is very recent and newly born. That's why the theorists and the experimentalists are not really cooperating very well. But it is changing, of course.
You're learning how.
Okay, I see. That is quite a difference. Now there was of course Nishina in the 1930s, building cyclotrons and things like that.
But the war —
Yes, destroyed his cyclotron.
That's right. Were there any stories concerning that that you know, or is that something I should talk with Dr. Koshiba about?
Stories about Nashina's cyclotron.
No, I don't know. It's old history, before I was born.
That's fine. Okay. By this time, you were completely into neutrino work, particle physics, that sort of thing.
You mentioned that you went from Brookhaven. How did you go to Brown from Brookhaven? What was the move there?
No. I was hired by Brown University after graduate school. Then Brown's part was to provide the experiment. So I was working not in a Japanese group, but in a U.S. group.
I see. And so White was at Brown?
No. White was at Brookhaven, Al Mann was at Pennsylvania, and Bob Lanou was a Brown professor.
Ah, that's Bob Lanou. And they were all part of the same group.
Yes, part of the same group. These three people were leading the experiment.
Now I understand. Okay. Did you have a term appointment, or did you have a permanent appointment?
No, I was hired as a post-doc in the first year. Then they promoted me to a research assistant professorship in the year after that. But six months after I moved to Osaka University.
And how did that happen? Did you apply?
Well, Osaka University is also a part of that experiment. Even though I moved to a different institute, I was doing the same thing as at Brookhaven.
You were still at Brookhaven but then you had shifted.
I changed to get money or — [laughs]
Did you have a hand to play in this, or did other people say that you should be paid by Osaka? What was the situation?
In Japan it is very difficult to arrange to get travel money.
Travel money, yes.
Professor Yorikio Nagashima of Osaka University was part of the Brookhaven experiment, and the leader of the Japanese group. He had difficulty finding money to send people abroad. So he asked his U.S. colleagues to hire Japanese people in the United States.
Who were already there.
Yes. When Nagashima started the experiment at Brookhaven, he was already at KEK. Finally, he moved to Osaka University. He then asked me to come back to Osaka. So I moved back to Osaka.
So these large multinational collaborations make it possible for post-docs to move around from institution to institution.
Yes. I think so.
Do you know others who pretty much did the same thing?
I don't know.
You were building equipment primarily at Brookhaven?
Making experiments where you were responsible for the —
For the liquid scintillator. Yes. Now what liquid was being used at that time? The liquid itself, the substance. It wasn't water, was it?
It wasn't water. It was based on pseudo-cumen. It's a kind of oil. You must have a fluor in it for small amounts of chemicals to be added to make the oil flush light.
Oh, from Krinkoff radiation.
Scintillation. Okay. So there are some chemicals added so that when electrons move through —
Mm-hmm [affirmative], or the particles passes, then you get light.
Okay. So then you started working for Osaka University at Brookhaven.
And so you must have spent a number of years at Brookhaven working for the —
Yes. I think three, four, or five years.
Four or five years, yes. Did you have intentions of staying in the United States, or did you hope to come back to Japan?
First I went to Brown University in the United States. I didn't think then that I could come back to Japan.
Because of the job situation.
Mm-hmm [affirmative]. So.
What changed that?
Professor Nagashima moved the KEK to Osaka and obtained an open position. I was very lucky in that sense. Some of my friends who went to the United States are still there. They may not have a happy job experience if they come back to Japan.
What happens to them? I mean, you were made a research assistant professor. Does the average Japanese physicist who goes to the United States attain this status; or do they put up with something not quite as good? Are they taken advantage of? What kind of experiences do they have?
What I heard is, on average, they take two terms as a post-doc. Each term runs for two years, so four years total. Then if they do not get promoted, they have to find another job.
Either in the United States or come back here.
Or come back here.
Yes. So there really isn't much security. And meanwhile they've spent four years of their lives. Yes. But you did come back, and you came back to the position at Osaka?
Yes, at Osaka.
That had been vacated by Yorikio Nagashima.
And was that as an assistant professor, or an associate professor?
The Japanese system is quite different from the U.S.. We do not have any assistant professor positions by that name, but I obtained a similar position at Osaka University. But it's not a professorship. But —
Were you working for a senior professor or working on your own?
No, I was working on the same experiment which was led by Professor Nagashima. In that sense, I was working for him.
I see. So you continued to work on the scintillation experiment.
Did you travel back and forth to Brookhaven?
Most of the time I stayed at Brookhaven even after I got the job at Osaka.
Eventually you got here. Now could you lead me through the steps of how that happened?
Yes. The experiment at Brookhaven finished around 1985 or 1986. I joined the experiment at Tristan, which is the e+e- colliding accelerator at KEK, Tsukuba. I did that for a couple of years. Then I moved to the ICRR here. The ICRR is the Institute for Cosmic Ray Research at the University of Tokyo.
Now these different positions, moving to Tristan and then moving here, were these positions that were announced and that you applied for?
No, the Tristan experiment is also led by Nagashima.
So you continued to collaborate or work with him.
Yes, at Osaka University here. But Yorikio Nagashima is also part of the Kamiokande collaboration.
Professor Yagashima has the Brookhaven experiment, the Tristan experiment, and Kamiokande. I first worked for him on the Brookhaven experiment, then I started to work on the Tristan, but my interest was with the Kamioka experiment.
And so you have a sort of patron, a senior physicist who wants, who sees you as somebody worth having as a collaborator. Is that it?
Finding this patron and then moving into the right position that serves him but also serves you. Does that make sense?
Yes, that makes sense.
I see. But then, once you were at Tristan, you found that the Kamioka or the ICRR was more interesting. This was originally a cosmic ray group at the University of Tokyo?
Well, there is a long history about the Kamiokande group. I think you had better ask Koshiba-san about that. But he retired in 1987, so let me tell you a bit about the story after 1987.
We were pushing the Super-K, already in 1988 or 1989. Of course, I had been working on the Kamiokande before I moved to the ICRR.
Yes. I was doing two things. Since Professor Nagashima was a collaborator, so also I was a collaborator of Kamiokande. Then the problem was the Super-K. The money required to build it was a hundred million dollars. It was not trivial to find an institute to ask for this amount of money from the government. Professor Koshiba belonged to the department of physics in the University of Tokyo of course. Originally, all of them were. But there were some hard times. The difficulty was to ask for money on behalf of the department of physics in the University of Tokyo for the Super-K. So we had to find some organization to support the Super-K, to make a proposal, and to present it to the government to get money. In the end, we found the ICRR as a host institute to ask for money for the Super-K. Then Professor Totsuka and other young people moved from the department of physics to ICRR. A year later, I moved from Osaka to ICRR. We made a kind of core to push the Super-K project.
Now who did you push it with, and what was your role in getting the funding? Did you play a role in getting the money?
Well, yes. Professor Totsuka also played a critical part. He was the leader, so of course he was pushing and doing many things.
Who is he pushing?
Who is he pushing?
There is a committee under the government to discuss the future of scientific programs in Japan. So we had to persuade that committee, and also we had to persuade our funding agent of the government. These people are not scientists; they have positions high up in the government, and hear from many committees as to which project should be next. We persuaded the scientific committee under the government to push our project.
And what is the name of that scientific committee?
Well, I know the Japanese name. [laughs] The Japan National Committee for Science.
Or for physics.
Excuse me, for physics.
Oh, I see. This is an interesting —
It's a poster, the 18th International Conference on Neutrino Physics and Astrophysics.
Yes. We just made it.
Yes. John Bahcall is responsible for this. So it's supported by the IUPAP, the International Union of pure and applied physics.
But the committee is the Japan National Committee for Physics. That's the scientific committee.
But then there is a political committee as well.
Is there a name for that?
Yes, I know the Japanese name, but —
Can you just pronounce it in Japanese?
Well, we call Singikai.
Maybe we could relate it to the U.S.
I don't know. It's entirely different from committees in the United States. For example, in the DOE there are many committees. Most of the members of those committees are scientists and experts in the field. In contrast, the committees under the Japanese government have to decide on the politics, and are made up of members who are not only scientists, but also of general people like the president of the Toyota Motor Company. Of course there is always an expert, but a mixture of members.
So government, commercial, military. Any military?
No, I don't think so, no military.
Okay, so government and commercial, some scientists and political people, people who have been elected into office?
So that kind of a mixture.
Yes. So we have to persuade those people.
Is that a better system? Or is it a system that you see the need for? Is it a good system?
Well, I think it's a matter of a wait and see. I think that things must be decided by scientists at the 80 percent level. If decisions are made by the scientist alone, he only sees his own field. Okay? So we need a more general opinion. On the other hand, if we have general decisions at the 80 percent level, they will not be good decisions; these people do not know science. I think in Japan we have too much in-fighting on these general discussions. Scientists in that committee must be expanded.
What are the kinds of questions though in pushing for the Kamiokande, for the Super-K? Did people on this committee say, "Well, why should we spend a hundred million on this when we can spend it on the Subaru telescope?" or "We could spend it on cleaning up pollution" or something. Is this the kind of argument that you have to address?
There are many committees to decide what kind of project to push. The Subaru and the Super-K projects were discussed in the same committee.
Pollution and other matters are discussed in a different committee.
So you're not in competition.
You're in competition with other scientific projects. Like ISAS or the space projects and things like that.
After seeing it and talking to you, I now appreciate how large an enterprise this is, not only in building it but maintaining it. It's a big, big enterprise. Now, the scientific reasons for building the Super-K. Could you review, as you understood them, those reasons?
The most important reason why we got the Super-K approved was the fact that we found neutrinos from supernova, 1987. As I said, many of the members on the committee are non-scientists so it is very important to have some evidence to make those people understand easily. Supernovae are very easy for people to understand the importance of science. On the other hand, it is difficult to persuade people why proton decay is important, or the CP-violation.
Yes. It is very tough to tell people why the parity violation or CP-violation is important, but it is relatively easy to explain why the neutrino burst from a supernova is important.
Now, Kamiokande II was built primarily to detect solar neutrinos.
No, primarily to detect proton decay.
Oh, the II was?
Yes. II was also. You can ask Professor Koshiba. He designed it. But the original motivation was for proton decay.
Exactly. But when that didn't work —
Well, it works. It set a limit, and then of course the minimal SU5 model is rejected by the measurements of Kamiokande. In that sense Kamiokande really did the job for proton decay.
Yes, I see. In Alfred Mann's book, he tries to say that when the GUT theory, the Grand Unified Theory, was modified to show that the proton decay actually had a lifetime a thousand times longer.
Longer than that.
Then people realized that you weren't going to observe anything with Kamiokande. That's the impression he gives me when I read the book, but you're giving me a different impression.
What I said was that the original prediction from theory is 1028 years. That was rejected by Kamiokonde II; theory was expanded, of course, to include the super symmetry and other fancy extensions in a theorist's mind. Then that makes the proton life longer by thousands times.
Yes. The super symmetry theory came out after Kamiokande had been making observations and not finding proton decay?
Well, I don't think the super symmetry is motivated by the proton decay. That is, the Kami has an origin from different places. They are motivated by the symmetry between fermion and bosons. So I think those things must be asked to the theorist.
But you're giving me the impression that the observations that Kamiokande made, the original Kamiokande, pushed theory — caused theory to change. Is that true?
Yes. The Kamiokande measurements make the theorist invent other theories to make the Grand Unification. That is true. But the super symmetry comes from different places. But now, as you know, those lines are merging, and predict proton decay even in super symmetry theory, much longer than the original SU5 theory.
Right. Which —
1034 or something like that.
But very close. Very close to the sensitivity of the Super-K.
Where do solar neutrinos come into the story? Were they ever a factor in the building of either Kamiokande II or of the Super-K?
Well, originally in 1987, we were making very effort to reduce the background. Then the people are aware if the energy threshold goes down below 10 MeV we are able to observe solar neutrinos. Okay? That time we know there is a solar neutrino problem, which is originated from the Davis experiment at Homestake mine in the United States using chlorine as a target. Then they observe about 30 percent of the solar neutrino flux predicted. So that is one of the motivations. We like to measure solar neutrinos. Then we started, when we started the solar neutrino measurement in 1987 — Oh, I tell you the truth, Alfred Mann joined the Kamiokande group after the experiment really started. So they joined the Kamiokande experiment and they brought the electronic system which was able to measure the timing information. The original electronics of Kamiokande were able to measure only pulse height.
Pulse height. Your English is a lot better than my Japanese. So the original was only a pulse height measurement.
Yes, not a timing measurement.
But with the Pennsylvania electronics, we could measure both timing and charge; it then became possible to reconstruct the low energy events. Low energy means the energy of the solar neutrino.
At the same time we were very successful in deducing the background level, mainly coming from radon in the water. So the energy threshold has gradually gone down from 9.4 MeV at the beginning, to 7 at the end of the Kamiokande experiment in 1994. So the Super-Kamiokande started with the energy threshold of 7 MeV; it is now 6.5 MeV, and will eventually get down to 5 MeV.
Yes. But it's getting there. Have solar neutrinos been detected?
Solar neutrinos are detected by neutrino-electron scattering.
The electrons travel at high speeds in the water, and then emit Cerenkov radiation.
So the Cerenkov radiation is detected by the photosensor arranged on the detector.
Photosensor on the what?
On the surface of the, inner surface of —
Ah. The inner surface of the chamber. Right. Did the measurements of solar neutrinos with Kamiokande II agree closely with Davis?
They were a little bit higher than what Davis observed. Davis observed say 25 to 30 percent, less than 30 percent; we observed 40 to 50 percent, between 40 and 50 percent.
But still a lot lower than theory.
Lower than theory.
Than theory predicted, yes. Were you already working here in 1984?
No, I don't think so.
Oh, you were not working here yet.
Yes, I was not working. But I know the story, so I can tell you what happened.
It took about two years to make the modifications to Kamiokande II, to reduce the background.
And to make the anticounters.
And to make the anticounters. The first measurements started in December '85, lasted through 1986, and Alfred Mann says — and this is on pages 72 and 73 — that the background was highly variable. The rates were far higher than the predicted signal, and that there was some difficulty between the Pennsylvania group and the Kamiokande group in interpreting what was the cause of this background. And he said at one point, "Patience with the other group," which would mean you guys, "began to wear thin." That there was some tension. Do you know anything about that?
I don't know about those touchy things. I think you better ask Koshiba.
I'll be happy to. Okay. You knew Alfred Mann through all of this time, though.
Well, I worked with him after 1979 at Brookhaven, so I know him very well.
It's purely coincidental that he started working here in collaboration with Koshiba, and your being here. Does your being here have anything to do with your knowing Alfred Mann?
No, I don't think so. I was not really motivated by Alfred Mann's joining this group.
Okay. What were your primary motivations for joining this group?
Oh, the neutrino oscillation of course. Because, as I said, at the Brookhaven experiment I had analyzed our data for neutrino oscillation. I am interested in the neutrino mass and oscillation phenomena. Then neutrino is one of the things, you know, there is an indication, then I think, I thought this is a place I should work.
So this was a better place to observe the characteristics of the neutrino.
So you were interested in the particle itself.
Not so much in the nature of the source of the particle.
No. At that time I was not interested in astrophysics.
Astrophysics, exactly. Yes, one of the things I am interested in is finding out how physicists get involved in astrophysics. And if you could give me some kind of an overview, a feeling for how you, as you moved here and began working with natural sources of radiation, i.e., the sun or whatever rather than accelerators, artificial sources, did this start changing your interest at all? Did you start getting interested in astrophysics? And if you did, how?
Well, yes. It certainly made my interest change. Of course I was motivated by the neutrino mass, not by the astrophysics, in joining this group and working on solar neutrinos. But now I am very much interested in the source itself. Because in the course of analyzing the solar neutrino data I had to know how the sun created neutrinos and I had to study a lot about star formation — the development of the sun and stars. I also had to learn how supernovae explode.
It's very interesting physics by itself.
How did you learn and become acquainted with the stellar model theory, or theories of stellar energy generation and that sort of thing?
Well, there were a bunch of textbooks, and I learned in seminars and lectures.
This would be at the University of Tokyo.
Well no, not lectures per se. Some visitor would come here and give us a lecture, or a seminar.
Was John Bahcall associated with Kamiokande at all when you came here? Or was it later?
Well, he is not really associated with our group, but we talk frequently. We have very friendly relations with John Bahcall. He gives us much information. When he wrote his computer code of the neutrino electron interaction with radiative corrections —
Computer code. He asked us to check. So we did and compared with our calculations and model. So we have an exchange of useful information. But he is not part of Kamiokande.
Okay. Now in your checking his code with the radiative corrections as you mentioned, that did reduce the predicted flux, didn't it?
It's a couple percent effect.
It's only a few percent.
So there is still a big difference between observation and theory. What do you feel about that? Do you feel that there are several types of neutrinos and there may be a type that isn't being detected, or that there is something wrong with the theory?
No. I tell you. Something must happen to, or in, neutrinos. Forget about the measurements of Kamiokande. There are four experiments now, four different experiments, measuring different parts of the solar neutrino spectrum. Then I would say that experiment using gallium sensitive to the p-p fusion reactions, neutrinos from p-p fusion reactions —
Proton-proton. These provide only 50 percent of what is predicted. We know what kind of nuclear fusion reactions are happening in the sun, grossly — there is a chain which is more or less known. The net result is 4 protons go to helium with the release of 26-point-some MeV energy, and 2 neutrinos which restrict the number of neutrinos versus luminosity. So if you look at that simple relation, you can't explain the gallium experiment. People tell us what we on the Kamiokande measure is the higher end of the solar neutrino spectrum, which may change due to different nuclear reaction rates, opacity, and other things. But it's impossible to change the main part of the solar neutrino reaction.
As far as the standard model is concerned.
Well, it's nothing to do with the standard model. It's just using the luminosity of the sun.
So it's a model independent of interpretation.
But the standard model is the proton-proton interaction.
Well, okay. If you say that, then it depends on the model in some sense. But what I said is that the standard model is the standard model of Bahcall and others. But other non-standard models somehow use the mixing of other things.
Right. Now, my question to you though is that, as you look at this, and when we started the interview, you felt, as you told me, that you feel it's very important to have a mix of observation and theory.
But here we have a situation where observation and theory just aren't cooperating.
Yes. I am very happy about it.
Why does it make you happy?
Because I had to learn the helioseismology and the nuclear fission reactions. Also to interpret the neutrino mass I have to learn a lot of new theories.
You had to do what?
I had to learn a lot of new theories, such as, the neutrino conversion theory.
And this was a challenge?
Do you feel that when something like this happens it is a key to new knowledge, that something very different may come out of all of this?
Well, I think in the end something new certainly comes out.
So things have to change —
Have to change.
In both areas, particle physics and astrophysics too. Okay. You mentioned before the collaborative experiment where a neutrino beam from KEK will be measured here at Kamiokande.
Is this part of the search? Because there you will have a calibrated source? Could you describe that project?
Yes. I have to tell you about another neutrino problem other than the solar neutrino. We have another problem called atmospheric neutrinos.
I haven't heard of this.
When primary cosmic rays, mainly protons, enter our atmosphere, they produce mesons, pions and kaons — the pions and kaons decay, and produce neutrinos, and muons. The muon also decays and gives another neutrino. I mean, there are two kinds of neutrinos produced in the atmosphere: muon neutrinos and electron neutrinos.
Electron and muon, right.
Then the decay, from pi's and k's, produce muon neutrinos. Then the decay of muon produce muon neutrinos, one muon neutrino and one electron neutrino. In the end, (it's not quite a quantitative argument; it's a qualitative one) you have two muon neutrinos and one electron neutrino. But the measurement itself you only see one electron neutrino and one muon neutrino.
So 50 percent of the muon neutrinos are missing. This is the so-called atmospheric neutrino problem.
It's another deficit problem.
Yes, another deficit. We interpret that as due to neutrino oscillation.
As being the cause of this.
But you don't know how it's caused, or why.
Well, the neutrino oscillations flying from the place where neutrinos are produced to our detectors, the neutrino changes its species. Okay?
Right. But this is a conjecture. You don't know this for sure.
Well, we don't know this for sure, but the new data from Super-K tells you that if you look at the neutrino event rate coming from the top and coming from the bottom, then the neutrino flux from the top is the same as predicted, whereas the neutrino flux from the bottom is only 50 percent of that.
That's from the top of the detector to the bottom of the detector?
The direction from the top and the direction from the bottom.
You mean when it's coming from the sky as opposed to coming through the earth.
Coming from the sky, yes, and coming through the earth. But produced in the sky on the other side of the earth.
Exactly. So the path length is different.
The path length is different.
Now, is the KEK neutrino beam going to be part of this experiment of studying neutrino oscillations?
Yes. Then the neutrino oscillation parameter is somehow characterized by the length between the detector and the neutrino source and the energy. We call this E over L. Okay? Then if you analyze the neutrino oscillation — which is not proved — but if you interpret the atmospheric neutrino as a neutrino oscillation, E is around the 1 GeV range, then L is 200 or 300 kilometers. This is a very important number, since the distance between the KEK and here is 250 kilometers. The neutrino beam they produce at KEK is 1 GeV. So exact matches. So if the atmospheric neutrino is really oscillating, we should see the oscillation in our neutrino beam from the KEK.
You should be able to see it.
And that's the purpose of this experiment.
So you're back to your primary interest.
Which is the neutrino oscillation. Oh, I see why you're happy. And what's the time frame for this? When is this going to happen?
Well, we are building the detector now, I mean the front detector. The Super-K is already running.
But we need another detector very close to the beam line, you know, at the production point, to monitor the intensity of the neutrino flux. We are making those detectors now. Then the experiment really starts, I mean the plan to start, in January of 1999, a year and a half from now.
Okay. Is there a lot of funding involved in this?
Yes. I think most of the money is spent to build the neutrino beam line. But the KEK does not have such a beam line, and so twenty or thirty million dollars were provided for building it.
How do you direct a neutrino beam?
Using a GPS (Global Positioning System) coordinate.
No, I mean if you produce neutrinos, how do you get them to move in a particular direction?
Well, we already have the direction. We use a proton beam.
A proton beam. Okay.
Then we have a target to produce the pions and kaons, but mostly pions. And pions spread like this way.
Yes, they do spread. Okay.
So we have the magnetic horn, we call the horn —
Magnetic horn, yes.
Yes, it produces a magnetic field which forces the pions produced from the target to be parallel.
Obviously anything charged you can focus.
Yes. Then we have some decay space, let those pions decay to produce muon neutrinos. So the accelrator only produced the muon neutrinos.
Right. And but they go in the same direction as the focused pions when there's nothing to change their direction. Now I see how you do it. Okay. I know a little bit of physics, but not enough. I see how it works. Okay, and is this your present project now?
Well, yes, we are now doing those things, so we are operating the Super-K and we are building the front detector and the next year the experiment we call the long baseline experiment will go forward.
Long baseline. Okay.
So we are involved with both.
Now, being involved in both, you are maintaining the Super-K now, that's part of your job.
And another part is developing the work with KEK.
I'd like to know what daily life is like for you. What is your position called here, and what are your responsibilities? What are the kinds of things you have to do?
I have the responsibility of the analysis group of solar neutrinos; I'm the leader of the group. We have a daily small meeting and a weekly meeting as an entire analysis group.
How many people in the group?
So you are not responsible for the maintenance of the instrument; you are on the analysis side.
Much of the maintenance is done by the young people, but I originally designed and checked the front-end electronics. Actually, I am not really doing that anymore. I ask the young people to do it and maintain it, but sometimes I have to work with them, because I am very knowledgable on the subject. But it doesn't happen often, everything is working fine; we only replaced ten modules in 15 months.
That's very good.
Basically we are not doing any maintenance jobs; we are just watching.
How many groups now are there? You're the head of the analysis group. What are the other groups?
We have three analysis groups
We are called the low energy group, that is what I am leading. Its main job is to analyze solar neutrinos. Then another group is the atmospheric and proton decay group, which is led by Professor Kajita, who you just met. Then the other one is the muon group, upward going muons.
Upward going means muons coming from inside the earth?
Exactly. That is also caused by neutrino interaction, which is led by Takita at Osaka University. There is yet another group, very important. Its name is the calibration group — essential for all of the analyses groups and all of the experiment. This group is led by Professor Nakahata. So Takita and Nakahata are very important individuals.
Then I also lead the ICRR group of the long baseline experiment. So I have two major responsibilities: to lead the analysis group, and to lead the experiment for KEK, the long baseline experiment.
What is the primary criteria for assessing the quality of your work at the University of Tokyo or here in this group? Is it the ability to perform analysis, or are you still under the evaluation that we call "publish or perish"? Are you evaluated by the number of papers that you publish and their quality, or by how well the facility works?
Well, I think it's very tricky to judge by the number of papers, unless you know the quality of the paper.
When we evaluate and discuss the quality of a scientist or the facility, I look at the ability to produce physics. Analysis is one of the major factors, but we must also have the ability to conduct the experiment. So we not only have to have the ability to analyze data and do physics, we must also have a knowledge of the hardware, understand a lot of components which are needed for the experiment. In addition, we need to have the ability to make plans and propose new experiments. I think that's very important for experimental physics.
So you see it as a balance of the two.
Yes, a balance of the two.
Otherwise we can't do the experiment.
Right. Now, as we took the tour today, which I again want to thank you for, you said on a number of occasions how important it is to have certain craftsmen.
Craftsmen. People like glass blowers.
Were you involved at all in the design or construction of the latest 50-centimeter phototubes?
No. The basic design was done by Professor Koshiba and the Hamamatsu company. We then improved them for the Super-K by changing the design of the dynodes and other details. Those details were done by Professor Suzuki, same name as mine, but Atsuto Suzuki. He is now at Tohoku University. He's the expert on phototubes.
Okay. And his last name is Suzuki. Okay. But you made a big point that there are only two glass blowers in this company that presently are able to make these tubes. This points out to me the importance of having craftsmen around. Are there other areas of technology that are this difficult to reproduce in Kamiokande?
Well, the electronics. We have 946 front-end modules, each module handling signals from 12 PMPs.
Phototubes. Okay? Then what happened is that it is very difficult to make entire set of new electronics for 11,000 phototubes. Okay? But the trouble is already happening. Some of the components — we have many ICs and RSIs and those things. Some of them are not sold at all, you know, they stopped producing. So we have to find replacements, or we have to make some very special ones for the fixing stuff. It's already happening.
Okay. You were talking about the difficulty that technology is changing so quickly that with 11,000 different sets of phototubes and their associated electronics and they all have to be the same —
Yes, we have to keep the old technology, rely on the old technology. That's a source of trouble in this kind of large scale experiment. You can't revise. Once you decide to change, you must spend millions of dollars.
Yes. That's exactly right. And how often does this problem come up? I mean you say the phototubes are very stable.
The electronics are also stable, and as far as I can see we don't have any serious problem in future, but it doesn't mean you know we can, we have to live with this situation. I mean sometimes we need to modify those electronics. For example the dynamic range of this electronics is limited to 300 or 600 photons right now. Then there may be a requirement to extend these maximum photons to be counted to much higher level, because we study the very, very high energy phenonema, then we need to modify those things. But by doing that, I think it is almost impossible to make modification. So we must invent some way to cooperate with those requirements. I don't know how we can do it.
So you have not made any upgrade at this point.
Not at this point. But in future we may have some difficulty to meet our requirements.
Yesterday you showed me the computer system, and you said you were upgrading it.
That's something that you can upgrade I take it.
Yes, we can upgrade the computer. That isn't a problem. But however, it may be a problem, because our software relies, I think we are using the kind of system dependent codes. Okay? So then we must keep the similar system goes with our new system.
I see. So there are problems, technical problems, interface problems, and software problems. All have to be of concern. You said that there is no longer a collaboration with Pennsylvania?
Why did that collaboration end, or how did it end?
I'll tell you what I know, but I suggest you discuss it with Koshiba.
This happened before you —
Yes. But I'll tell you something. When Koshiba started the collaboration with Pennsylvania, he made an agreement with Alfred Mann. Once the Kamiokande measured solar neutrinos and made the flux measurement, then the collaboration with Pennsylvania was finished.
Oh, so it was a finite collaboration.
Yes. A finite agreement.
But you better ask Koshiba. He may have a different or confidential story.
I might get a nuance to the story.
Okay. The idea that they set it up at the beginning that way is what I can ask him.
But it worked very well.
Why was the collaboration needed?
Well, of course Alfred Mann approached Koshiba to let Pennsylvania join. I mean Al Mann's interest in that. Then what they said is they promised to bring the electronics which would be able to measure the timing. So that's why, you know, Koshiba required the upgrade of the Kamiokande detector. Then Al Mann's interest in joining.
Collaborations are done for many reasons. Sometimes two groups get together because one has a specialty the other one does not have. Was the timing electronics a specialty that Mann's group had that you did not have, or could you have done it, or was it an economic collaboration?
Yes. Once we had the money, I think we could have made the electronics. But you know, since the Kamiokande is not really supported very well —
The original Kamiokande.
They made a lot of attempts to get the necessary money, but were unsuccessful. But young people like Totsuka were against the collaboration.
Yes. He stated, "We can make the electronics. Why don't you let us work on the electronics?" But for political reasons, Koshiba decided in favor of collaboration. You better ask him.
Okay, but it does agree with what Alfred Mann said in his book. That Koshiba convinced his younger staff that they should collaborate and provide the Pennsylvania staff with all of their technical knowledge their knowledge of how Kamiokande works. But it implied that some were resistive. He didn't say it, but he implied it.
Let me ask you about the different ways of detecting neutrinos. I mean there was the Davis experiment. There was the the liquid scintillator that you worked on at Brookhaven —
No, that was for the accelerator neutrinos.
For accelerator type neutrinos. That wouldn't work at all for celestial neutrinos?
Well, it works. And one of the projects, called Borexino, at the Grand Sasso Laboratory in Italy uses a scintillator to detect solar neutrinos. But it's not working out yet.
That's not the gallium.
Not the gallium. Grand Sasso has two solar neutrino experiments: the gallium experiment and the Borexino, using a liquid scintillator. But Borexino is still in the constructing phase. It's not taking data at all.
Right. And then there's the water detector.
Yes, right, the Kamiokande.
Now, does each one of these systems have certain advantages, disadvantages and that sort of thing?
What, for example, are the advantages of the water detector?
Well, first the original chlorine detector could say there was something in their detector, but they couldn't tell where those things come from.
Okay? They just count the number. But then the water detector has a directionality measurement so you can identify where the source of neutrinos comes from.
We can identify the direction of the sun. We can even see the picture of the sun by neutrinos. I call it the neutrino heliograph. [laughs]
Neutrino heliograph. Interesting.
[laughs] Yes. So it's one of the advantages. You can see the direction. Then another advantage is that we have real time information, the time when the interaction happens. This means we are able to make measurements to study the time variation of the flux. For example, if there is a seasonal variation, if there a the variation due to solar activity, there may be a flux difference between daytime and nighttime. It's important. Nighttime neutrinos pass through the earth, so another neutrino oscillation phenomena, you know, the, we call the regeneration of solar neutrino through the earth.
So solar neutrinos, as present interpretation, are born as electron neutrinos, and become muon neutrinos through the travel within the sun, then at the surface they become the muon neutrinos. Then that comes to the earth, of course it oscillates between the muon neutrino and the electron neutrinos —
That's the electron oscillation you are talking about.
Mm-hmm [affirmative]. But entering into the earth, those muon neutrinos go back to the electron neutrinos because of the mass effect of the earth. So that we call the regeneration of solar neutrinos through the earth.
If that happens, the flux between daytime and nighttime is different. We are the only experiment which can measure the daytime and nighttime fluxes.
There are two gallium experiments. One is in Italy, at the Grand Sasso Laboratory; so the experiment's name is Gallex. The other one is called Sage, at the Boksan Laboratory in Russia. Okay. So Sudbury has now almost completed their detector. They probably will start the experiment by the end of this year. They use heavy water.
Why is heavy water better than regular water?
Well, they detect different interactions called neutral current.
Yes. Which gives same interaction rate to any neutrino species. So whatever happens on the neutrinos, neutrino goes from electron neutrinos to muon neutrinos and muon neutrinos to electron neutrinos, whatever, then they get the same rate, same neutral current interaction rate. So that is used as a standard or normalization of their measurement. Then they also measure the usual interaction specified for electron neutrinos, then they compare those interactions, they are able to judge if neutrino oscillation is really happening or not. So it's a different, completely different detector, even though it looks like water. Heavy water gives you a different handle on the measurement.
But they're using phototubes as well.
I guess this is a question for Professor Koshiba, because the collaboration with Pennsylvania was described also as being with Ni-igata, with KEK, and with AT&T Laboratories in New Jersey.
No. It was with only a single person, who was in Pennsylvania probably. He moved to AT&T, something like that.
Ah, okay. Okay, so it wasn't a major collaboration.
Okay. They listed those. In 1987 Koshiba called for a worldwide network of Super-Kamiokande type detectors in Japan, USA, Europe, and Australia. This was in Physics Today, 1976.
Yes, I remember that.
He said it was his dream. It didn't happen: there are many different types of detectors in existence today. Why do you think this is the way it's turned out, and not more Super-Kamiokandes?
Well, I don't know if it's turned out or, you know, I don't even think he was seriously thinking about those. For me it is not clear what is the purpose of those detectors. So I don't know. He must spend another hundred millions and two hundred million dollars to build a detector, but what is the purpose? What is the aim of the physics?
Right. So what would be the aim of having a lot of Super-Kamiokandes.
Yes. So I'm not so sure it justifies the expenditure of several hundred million dollars.
So you see more value in the way it's turned out, with a lot of different type of detectors.
In 1996, John Bahcall and Totsuka and two or three others wrote a article on neutrinos, the state of neutrinos, and he said thatC
Who is that?
Bahcall. He actually wrote the article I think, and he said that most physicists and astronomers now believe that the observational discrepancies between theory and experiment are not in the standard model but — and I'm quoting him — "our overly simplistic view of what neutrinos can do after they have been created." And he feels that we need a better knowledge of electro-weak interactions. Do you agree with this?
Yes, I think I agree with that.
He's basically putting the challenge to experimentalists to fix the discrepancy. How do you feel about that, and is it the sort of thing that you think is a positive step?
Well, he made the statement three years ago, right? No, last year, but actually it was written two years ago.
Two years ago, yes.
The validity of the standard solar model is much, much stronger since a fair amount of the analysis went into the helioseismology. That, plus the major work done by Dziembowski and colleagues, now predict the sound velocity in the core region. The core region is actually the place where the neutrino is produced.
The agreement between the helioseismological observations and the standard model prediction is very good.
And that's based upon direct observations.
And the acoustic characteristics lead to that. Okay. So this statement then you would agree with.
Yes. At this time. And he was saying things could be looked at in terms of neutrino mixing in the sun or effects in the travel between the sun and the earth, and evidently these are the things that you're looking at with neutrino oscillations, what causes a neutrino to change its flavor or its character.
Yes. How do you see research in the future developing? What do you think is going to happen? I know it's hard to predict.
Well, I think as far as the solar neutrino is concerned, even though the standard solar model is very solid these days, but as an experimentalist we like to establish the solar neutrino oscillation by the data itself. Which means what we are doing is to measure the electron recoil. We measure the neutrino electron scattering, so what we measure is the electron energy spectrum. So since the, if the oscillation is really happening, those electron spectrum is distorted from the prediction, which is entirely free from, independent from the solar model. Those spectrum is determined by nuclear physics. The beta decay spectrum gives you the shape to be observed. So once you find the distortion and the deviation from the shape predicted, it's a direct evidence of the neutrino oscillation.
So that's what we will be doing in a couple of years from now.
Working along the lines you are working on now. At this point in your career, do you treat this as pretty much your lifelong work?
Yes, it may be a lifelong project, because the neutrino mass is very important both particle physics and astrophysics. Okay? Then we may change the theory of elementary particle physics. So then what is happening in our experiment is now is we have two independent evidence or suggestions of neutrino oscillation and neutrino mass. One in the solar neutrinos, the other one in atmospheric neutrinos. So I think it is very much a part of my career; This experiment. We are so much lucky. I mean it never happens, this kind of good situation, so I would like to stick to this business for time being. So it is very important, and it is good, and I am very happy about this situation.
Now, in your life you spend half your time here, you say it's one month here and then one month back at Tokyo?
No, I commute every week almost.
And you fly every week.
Yes, I fly back and forth.
What impact does that have on your family, on your personal life, and what do you do when you're in Tokyo when everything is here?
I stay in my home in Tokyo and spend many hours with my family of course. I try to be with my family as long as possible.
Oh, I see. So in the week that you are in Tokyo you are with your family more than at the university.
Well, not really, I work at the university, but I try to come back to my home earlier than the usual time.
Oh, you come home late.
What is your typical day like then? You go to work at about what time?
About 9 o'clock.
And when do you get back?
I get back about 11 o'clock or midnight.
Ooo! So when do you see your family?
I try to make that time earlier so I can return to my home around 8 or 9 o'clock. At least I am making an effort. Some days I fail.
So you're saying that the typical physicist or faculty member at the university doesn't get back home until 10 or 11 o'clock at night.
Mm-hmm [affirmative], I think so.
And it's work all the time?
Yes, work all the time.
My wife sort of works that way, but I don't. I try to get home earlier. But sometimes it's very difficult. Now you don't have students. You don't teach.
I do have graduate students.
And what is your responsibility toward them, and how do they work with you?
Well, I have to somehow direct them to an interesting field. Then I have to teach them in the laboratory. They spend about eight hours per week there. Eight hours a week or so.
Oh, and this is the laboratory at Tokyo.
But I ask another person to teach them sometimes: of course, we have at least one research associate at Tanash all the time.
That is the campus?
The campus at Tokyo, in Tokyo. We call it the Tanash Campus.
So there are many different campuses to the University of Tokyo.
Yes. The cosmic ray institute where we belong is on the Tanash campus. It's not the main campus.
Yes. Now, in the cosmic ray group are there people who are specifically interested in cosmic rays?
Yes, traditional cosmic rays. There is such a group.
Do they fly balloons and that sort of thing?
Yes. Some of the group mounts detectors on the balloons. They then measure cosmic rays. The other group is measuring gamma rays using the grand array or air Cerenkov telescope.
And another group is measuring the very highest air showers, air shower arrays spread over 100 kilometers square, square kilometers. So they detect the highest energy cosmic rays, about 1020 electron volt. So it's the highest energy ever observed.
That's right. This is a very large group of people.
Yes, it's a large group.
Who is the leader of the group? I mean the whole ICRR.
Well, we have a director. The director is Totsuka now.
Okay. So he directs everything.
Directs everything. So you missed your big shot.
So he directs the cosmic ray balloon groups as well as the gamma ray group?
Well, not really directs; he oversees.
He oversees it all.
He is not involved in each experimental group of course. As a director, he oversees and then establishes some guidelines, but that's it.
Each experimental group works independently.
Okay. Yes. Now each group has to raise money, and as I understand it, most of the money comes from the Ministry of Education, Culture and Science in Japan.
Yes, that is our funding agent.
Right. Now this funding agent, is this the funding agent that Koshiba also had to go to, and is part of that committee structure that you described to me?
Well, that depends on the amount of money. If the amount of money is like a hundred million dollars, like Super-K, you must go through that procedure. But if you are talking about one million or maybe less than ten million dollars, it's much simpler. You don't need to pass through those committees. You ask money, you know, there is more than one channel, even though all the money is coming from the Mumbisho, that funding agent.
One is a channel for very big money; the other is for smaller projects.
And so the smaller projects go through project managers or program managers?
Yes. They have to judge which project is to be picked up, but the discussion is much, much simpler. Also they are all scientists and physicists.
Okay. So it's peer reviewed primarily.
Peer reviews, yes.
On panels that are chosen by the ministry.
But the ministry must ask some professional organization for the names of potential panelists.
And what professional organizations do they turn to, to choose the names for the panels? Is it the physics community in Japan or what?
One of the divisions of the funding agent selects those people on the committee.
So, it may not be the democratic way.
But this is the way it works.
Okay. Is there anything else that I should know about in appreciating the present Super-K and the whole infrastructure here, something I haven't asked, something I've missed?
Well, I don't know.
Do you have such things as public information officers, people who deal with the press?
We have only 12 physicists working in this laboratory.
Yes. Then we hire some three or four peoplen to help us. That's it. So we do not have people devoted to public relations.
No public relation sort of thing. But the university does.
The university does.
The video you showed me today, that must have cost quite a bit of money to produce. Was that something that Professor Koshiba or Totsuka created?
No. We asked a private company to give us the money.
Who did that?
Totsuka and myself.
And you went to a private company.
Oh, to, to —
Produce such a movie.
Who was that private company?
Mainly they built our detector. Hamamatsu gave us the money. So one of the companies that built our electronics gave us the money.
Of course we did that after the fact.
Yeah, but all of those pictures though, that footage was taken while the Super-K was being built. But the money I guess was already in place.
Company Hamamatsu. It's the name of a city.
Is it a big company? Do they do a lot of different things, or do they specialize in detectors?
They make the phototubes of course. Also, they have a big division working on solid state.
Gallium arsenide. They also have a solid-state laser, and some other things.
Okay. So they are sort of a high tech company.
Yes, high tech company.
And this is the same company that made the original phototubes for Kamiokande?
So I would ask Professor Koshiba about the details of that.
Okay. A final question then. What is it like to deal with the miners and the mining company today? Are you responsible for that, or is that Totsuka's responsibility?
Okay. But as far as you know, since I can't ask him, how are the relationships? Do you write a contract with them each year, or do you do a 5-year contract?
We made the agreement and contract at the beginning of our fiscal year. But once we made those contracts, we simply extend them every year. But we can, of course, modify them if necessary.
Have the relationships between the company and the scientists been good?
Yes, very good. They help us a great deal.
What's in it for them other than a little bit of money? Is it a major source of revenue for them, or do they do it for other reasons?
Well, as I said, they are still operating the mines in the different places. They have different mines spreading all over the place around here, so they only closed this mine. So they are still operating other mines. I think the money we are giving them is only a fraction of their operation. So not a large fraction I think.
Not a large fraction. As you said before, the Mitsui Company oversees all of this, and it's a huge company.
Do they get any public relations out of this? Have they ever used the supernova in their advertisements?
I don't think the Mitsui Company did that, but Hamamatsu did. [laughs]
Well okay, they have a much better reason to. Well, we've gone over two hours, and thank you very much.
Yes, it's the right time.
It's the right time. Okay. Well it's been a wonderful interview. I want to thank you for all your help, and I want to stop this, and I've been, I want to give you something. I just want to say on the tape first of all that I am going to be having this interview transcribed onto typewritten paper and we'll send you a hard copy so that you can read it, maybe clarify some of the points, change your mind, say something differently, so that we can put it in final form for deposit. And this process will take a few months, I'm sure. Is that okay?
Okay, great. I'll stop the tape now. The interview is over.