2 febbraio - 20 maggio


Ryugo Hayano is professor at the University of Tokyo and he is currently dealing with "exotic atoms" together with his group of research.

Here is the interview to professor Ryugo Hayano, who e-mailed us about him and his job.

1952 - Born in Gifu, Japan
1974 - Bachelor (Physics), The University of Tokyo
1979 - Ph.D (Physics), The University of Tokyo (I did most of my thesis work in Vancouver, Canada, and defended my thesis in Tokyo)
1979 - Research Associate, The University of Tokyo
1982 - Associate professor, National Laboratory for High Energy Physics (KEK), Japan
1986 - Associate Professor, The University of Tokyo
1997 - Full professor, The University of Tokyo


1998 - Inoue Science Award (for the discovery of Sigma hypernuclei and antiprotonic helium)
2008 - Nishina Memorial Prize (for the study of antiprotonic helium atoms). This is the most prestigious physics award in Japan.

Q: How and why did you decide to study physics and which is the best memory of your life as a student?

Just before my 5th birthday, I started to take violin lessons. I practiced very hard, and became fairly good at it. My violin teacher, Dr. Shin’ichi Suzuki, took me on a concert tour throughout America together with nine others in 1964; it was a phenomenal success. However, I never seriously thought about becoming a professional violinist. My father was a professor of medicine. My mother also graduated from a medical school (although she chose to stay at home after marriage). So, I was quite naturally attracted to science in my childhood. I read all sorts of science-related books. I was also a fan of taking things apart (and often failed to put them back to the great embarrassment of my parents). At school, I loved math and physics, because I could understand and solve problems based on a very few principles; I did not much appreciate other subjects which forced students to just memorize things. At age 18, when I was to choose my future, I was still undecided whether I should go to a medical school or to a science department. It was my father who advised me to choose basic science, saying, “If your dream is to become a researcher rather than to practice medicine (to attend to patients), why waste extra years to obtain the medical practice license?” I knew, observing my father, how strenuous it is to be doing research, teaching students and seeing patients at the same time. In my childhood, I rarely saw him at home. I respected him, but I wanted to lead my life somewhat differently. My girlfriend (who after about ten years became my dear wife) was also of the same opinion. So I chose science rather than medicine. It was after entering the University of Tokyo that I got attracted to physics.
I already knew that mechanics and electromagnetism that I learned at high school are not “modern”, and hence it was a thrill to be exposed to quantum mechanics and relativity (although it was daunting to realize how much more I must study before I can actually start working on the “frontier” subjects). When I was a senior (4th year) student, I met my mentor Professor Toshi Yamazaki (who later became my collaborator and friend as well). His group was then at a small cyclotron facility, which was used for medical purposes during daytime, but was free for us physicists to use at night. Toshi himself was not frequently available at the lab. I took advantage of his absence, and learned how to operate the accelerator, and also how to fix it. There was also a small computer in the lab, one of the first affordable “mini” computers, which was about the size of a bookshelf, with only 0.12 megabytes of memory, without a hard disk (only paper and magnetic tape drives), and must have cost the equivalent of some 100,000 € - the state of art in early ‘70s. I taught myself to program this machine, and wrote some programs for analyzing data taken at the cyclotron. All this was so exciting to me, and I literally “lived” in the lab. In 1974, I chose Toshi Yamazaki as my Ph.D supervisor (or rather he accepted me as his student). However, when I reported to his office on my first graduate- school day, I found that my supervisor was absent, but the office was instead occupied by a professor from Germany. This was Professor Paul Kienle, who I understand is also contributing to this interview (he has become my collaborator and friend). It was not common to have foreigners around you everyday in Tokyo in early ‘70s, and having a German physics professor as a supervisor, although tentative, was unheard of. Since other (older) students in the group were rather hesitant to talk to Paul, I was the one who communicated with him the most. I don’t remember doing much physics with him, but we frequented bars, and had lots of fun. Later that year, Toshi told me to come to Berkeley where he was running an experiment, which I enthusiastically did, and just after my arrival, something exciting happened; people were running around, and were having heated discussions everywhere. This was the day when a new particle ( Ψ - psi) was discovered at SLAC (Stanford Linear Accelerator), the historical event now known as the “November J/ Ψ revolution” of particle physics. Being an yet untrained, ignorant first- year graduate student, I was unable to fully understand the cause of the excitement, but I could sense that something important - worthy of a Nobel prize - was discovered. I was fortunate to be a part of the scene. Soon after the November revolution, Toshi moved to Vancouver, Canada, where the new powerful “TRIUMF” cyclotron was about to be completed. He told me to come, so I bought a small car in California, and drove to Vancouver. Toshi and I together waited for the first beam to come out of the cyclotron for many days, in vain. Not much could be accomplished before Toshi went back to Tokyo after about half a year, but I continued to stay in Vancouver for (most of the) following four years, until I completed my Ph.D thesis. I was the first student to get a degree using the data taken at the TRIUMF cyclotron. All in all, I was quite lucky to have excellent mentors, and was lucky to be introduced to the international environment of physics research at the very start of my academic career.

Q: Which difficulties did you have to face and what was the most exciting episode of your career?

There are many difficulties, but I am optimistic enough to forget them. Usually that is. Of course there were times when my research seemed to get nowhere. I got (mildly) depressed, and thought, “Oh, I must have made a wrong decision. If I were a medical doctor, my life would have been more meaningful. What’s the use of a physicist who cannot discover ...” Those were the days. Nowadays, difficulties are mainly financial. Experiments require funding, and our experiments tend to cost morethan experiments in other physics fields such as solid- state physics, quantum optics, etc. To get funded, we must apply by writing a research proposal, get reviewed, interviewed, and so on, every 3 to 5 years. Competition is severe. Should l fail, it will be devastating to my group. Without money, there will be no research outputs, and without anything to show, my next proposal is more likely to fail than to succeed (commonly known in our trade as the principle of “publish or perish”). Luckily, I have never been in this down-fall spiral, but it really is a nightmare. Now about the exiting episodes. I was lucky enough to make several “serendipitous” discoveries, that is to find something which was totally unexpected. Let me briefly tell you how it was with my first serendipity. This was when I was in Vancouver, struggling to find the subject for my thesis. Toshi, my supervisor, was far away in Tokyo. There was no internet yet and international phone calls were prohibitively expensive. We communicated using airmails, which were often disrupted by the (rather frequent) postal workers’ strikes in Canada. Please bear me, this is going to get a bit technical hereafter: Toshi pioneered a new field called “µSR” (muon spin rotation) at TRIUMF, a powerful method to study magnetic properties of substances using accelerator-produced muons (µ is a weightier brother of an electron). In this method, a magnetic field is applied perpendicularly to the muon beam direction, in which the muon “spin”, which is originally oriented along the muon beam direction, precesses. Measurement of the muon spin precession frequency uncovers details of the internal structure of the material in which the muons are brought to rest. For several reasons (but certainly not for making the discovery I am about to describe), I constructed a relatively simple setup to apply a magnetic field along the muon beam direction rather than perpendicularly (in which case muon spins are not expected to precess). However, when I first took data without applying the magnetic field (just to test detectors), I was surprised to find that spins appeared to be slowly precessing - not many times like in the case of ordinary µSR - but about half a turn. I sent the data to Tokyo, where my supervisor showed it to his theory colleague in the faculty, Professor Kubo, who, as I heard, got very much excited. It turned out that Professor Kubo once worked on a problem of “zero-field” spin behavior (in his case it was nuclear spin rather than muon spin), but had dismissed it (and almost forgot about it) as being a purely academic problem which can never be experimentally tested. A message from Tokyo read, “Tantalizing. Is it possible to check if the spins rotate more than 180 degrees?”. This I did immediately, and found, indeed as predicted by Professor Kubo, that the spins do make nearly a full turn. This was a very exciting moment. By pure accident, I invented the “zero-field muon spin relaxation method” (this is the term I used in my paper), and with this discovery, I earned my degree with ease. My thesis, published in the “Physical Review” journal in 1979, has become a “classic”, and is still one of the best-read paper of my work. The “zero-field” method is now a standard tool to study, e.g., high-temperature superconducting materials.

Q: What are you working at presently?

I study “exotic atoms”. In ordinary atoms, electrons orbit around the atomic nucleus. If instead a negatively-charged particle such as an antiproton (the antiparticle of the proton, having a negative charge but the same mass as the proton) is bound to the nucleus, we call such a system an “exotic atom”. Exotic atoms do not exist in nature. They must be artificially synthesized using accelerators. You might ask why it is of any use to study such things, if they are not the building blocks of the universe. Good point. It turns out that “atomic spectroscopy” techniques, the methods to study the discrete atomic energy levels by observing the “atomic transitions” (emission and absorption of light quanta by the atom), which is the established method to study ordinary atoms, can be applied to study exotic atoms (sounds simple, but in reality, it took us many years to develop such techniques). Our data can then be used to test fundamental symmetries of nature, such as the matter-antimatter symmetry. One of the central questions is, “is the proton mass exactly the same as the antiproton mass?” This is one of my main activities, which is being done at CERN (European laboratory for high energy physics), Switzerland. My team, called “ASACUSA”, has been working on the laser spectroscopy of antiprotonic helium (in which one of the two electrons of an ordinary helium atom got replaced by an antiproton), and has measured the antiproton mass almost as precisely as the proton mass. By the way, the antiprotonic helium atom is another example of our “serendipitous” discoveries. At CERN, we established that the antiproton mass and the proton mass agree with each other to 10 decimal places, and our measured antiproton mass, together with the best measurement of the proton mass, is now used in the determination of the internationally adopted “fundamental physical constants”, the cornerstone of modern physics and the foundation of the international metric system of units “SI”. For this work, I was recently awarded the prestigious Nishina Memorial Prize.

Q: Which do you believe will be the next discovery in physics?

The Higgs particle. This will be an important discovery but may not be world shattering, since the HIggs is already an integral piece of the so-called “Standard Model” of particle physics. Few physicists seriously doubt its existence. More interesting would be the discovery of “supersymmetric” particles. Many theorists believe that every known particle has its “supersymmetric” partner. For example, the electron may have a partner called a selectron, the photon (light quantum) may have a partner called a photino, etc. Discovery of any one of such partner particles will drastically alter the way we look at Nature. CERN’s Large Hadron Collider (LHC) is considered to be powerful enough to discover such particle(s) should they exist. And if our experiment ASACUSA finds that the antiproton mass is different from the proton mass, however tiny the difference may be, this will be a Nobel- class discovery (I admit this is a long shot).

Q: In your opinion, which is the best discovery ever and who is your favorite scientist?

Big Bang. How this world was created and how we came into existence is a fundamental question, which so far has been in the realm of mythology and religion. Physicists and astronomers have now established, quite firmly, that our universe was created in a Bang 13.7 billion years ago, and that fundamental physics laws can be used to understand (to some extent ... this is still a work in progress) how the universe evolved out of a high-temperature fireball. It is interesting to note that Einstein, whose “General Relativity” theory is inevitable for our understanding of the universe, strongly believed that the universe must be eternally constant (for aesthetic reasons). He erred. This again shows the importance of experiments and observations. My favorite scientist? I have not just one but many (there are so many great minds - giants - in the history of science), but let me name one Italian and one Japanese. Enrico Fermi. His textbooks (“quantum theory of radiation” and “nuclear physics”) appealed to me very much when I was a student. I wished I could be like him who excelled both in experimental and theoretical physics. Masatoshi Koshiba, the Nobel laureate of 2002 for the detection of supernova neutrinos using the “Kamiokande” detector. I’ve known him since my undergraduate days in Tokyo, and I vividly remember when he told us his plans to construct the Kamiokande detector. I later became his colleague as a faculty member, and I attended the press conference held in our department when the Nobel was announced. I’ve always admired his vigor and vision.

Q: How important is the collaboration in scientific research, especially among researchers from different countries?

In my field, which relies heavily on accelerators, international collaborations are essential. For example, if I come up with an idea for a new experiment for which however there is no accelerator within Japan which can fulfill my requirements, I don’t hesitate at all to go anywhere in the world where there is a suitable machine. This attitude I learned from my mentor Toshi Yamazaki. My students have therefore worked in Germany, US and Switzerland (and in Japan, of course). One of my current students, originally from China, is now working on an experiment being done at Frascati, RM. Science is borderless. When we work in such international collaborations, we communicate in English. For example, on the first page of the logbook of the experiment we did in Germany (logbook being a thick, sturdy notebook in which we jot down everything we did, learned, found, etc., during the experiment), we wrote: “No German, No Japanese”.

Q: How can a scientist be defined and how do talent, intuition and study influence his profession?

Scientists are people with passion for finding out the truth, who have been trained (through hard work) to acquire the means to attack the problems. Being an experimental physicist, I strongly believe in the power and importance of experiments to uncover the secrets of Nature. Curiosity drives us. Study naturally follows. That is: we often hit an obstacle, and struggle hard to overcome it. This is when we are motivated to study, learn something new. There are textbooks for physics, math, etc., but there are no “how-to” books for becoming a good & successful scientist. This is not something which can beeasily taught. However, it can be, sort of,“inherited” from your mentor. I am not saying that you should become a clone of your mentor, as it is essential in physics that you do something original. But if you meet a mentor, who (hopefully) is a world-class scientist, you have several years to observe what it takes to be such a world-class scientist, why he/she is great, what he/she has done (or not done), etc. Your mentor can be used to measure up yourself; in order to be a world-class scientist, you must become “better” than your mentor some day.

Q: What are your hobbies and passions and what book would you suggest us to read?

The beauty of being a scientist is that there is no real distinction between work, hobby and life. Physics is always in the back of my mind. We physicists do what we love everyday and get paid. Wonderful, isn’t it? I am a gadget freak, so to speak. I am interested in all sorts of new toys, computers, digital cameras, etc., but since I use such gadgets heavily in my research, I wouldn’t consider this to be my hobby. I wish I could say music (violin) is my passion (beside physics), but unfortunately I cannot play the instrument now (as I live in the center of Tokyo, where playing musical instruments is strongly discouraged). I save this pleasure for my retirement. I am a regular theater goer, in particular to the traditional Japanese “Kabuki” plays. I used to teach a “Kabuki appreciation” class at my university, in which I took science students to Kabuki theater every month. This was a very popular course. Oh, about the book. Let me see ... may I suggest “The Prism And The Pendulum: The Ten Most Beautiful Experiments In Science” by Robert P. Crease? This I chose because I am in experimental physics. The book is well written, and should be understandable to high school students. If I were allowed to name another, let me recommend a book written by a Japanese author. It is “Quarks: Frontiers in Elementary Particle Physics” by Yoichiro Nambu, the Nobel laureate of 2008, who earned his Ph.D from Tokyo University in 1952, the year I was born.

Q: How do you see the future of research in this period of global economic crisis?

Science shapes our future. Governments nowadays seem to understand this, so that they usually do not drastically cut research budgets in difficult economical situations. This does not mean however that we can take the government’s support for granted. We scientists must explain to the society what we do, and why we do it, and we must do everything we can to attract talented young people.