2008 NOBEL LAUREATES The Nobel Prize in Physics 2008 LIBRARY PHOTO KULYK/SCIENCE MEHAU “for the discovery “for the discovery of the origin of the mechanism of of the broken symmetry spontaneous which predicts the existence broken symmetry in of at least three families of subatomic physics” quarks in nature” (KEK) NIVERSITY RESEARCH ation U Z yoto K organi accelerator ENERGY IGH H LLOYD DEGRANE/THE UNIVERSITY OF CHICAGO LLOYD Yoichiro Nambu Makoto Kobayashi Toshihide Maskawa 1/2 of the prize 1/4 of the prize 1/4 of the prize Born: 1921 Born: 1944 Born: 1940 Birthplace: Japan Birthplace: Japan Birthplace: Japan Nationality: US citizen Nationality: Nationality: Current position: Japanese citizen Japanese citizen Harry Pratt Judson Current position: Current position: Distinguished Service Professor Emeritus, Professor Emeritus, Professor Emeritus, High Energy Accelerator Yukawa Institute for Enrico Fermi Institute, Research Organization Theoretical Physics (YITP), University of Chicago, (KEK), Tsukuba, Japan Kyoto University, Japan Illinois, USA PHYSICS 1 Copyright © Nobel Web AB 2008. Nobelprize.org, Nobel Prize and the Nobel Prize medal design mark are registered trademarks of the Nobel Foundation. 2008 NOBEL LAUREATES Speed read: The importance of asymmetry uckily for us, the Universe is not symmetrical, would have resulted. Instead, a small imbalance, or at least at the subatomic level. If it was, the asymmetry, in the amount of matter and antimatter L newly formed matter at the Universe’s birth created led to a slight excess of matter, from which would have been annihilated by an equal and we are all eventually formed. Such so-called ‘broken opposite amount of antimatter, and nothingness symmetry’ is one key to our existence. Understanding symmetry, or the lack of it, is an ongoing task, and the 2008 Nobel Prize in Physics rewarded two discoveries concerning symmetry violation in the field of particle physics. In the 1960s Yoichiro Nambu, who had been working on asymmetries underlying superconductivity, was the first to model how broken symmetry can occur spontaneously at the subatomic level. The mathematical descriptions he formulated helped refine the standard model of particle physics, the current working theory that best explains much, but not all, of the way that fundamental particles and the forces that govern their behaviour interact to create the known Universe. In the early 1970s, Kobayashi and Maskawa formulated a model that explained certain symmetry violations that had recently surprised observers in particle physics experiments. Their model suggested that the collection of subatomic particles known at Tsung Dao Lee and Chen Ning Sheldon Glashow proposes how two of Building on Glashow’s theories, Yang propose that the laws the four fundamental interactions in Steven Weinberg and Abdus Salam of mirror image symmetry nature, electromagnetism and the weak formulate the unification of the are broken in the world of interaction, are unified, on the basis of electromagnetic and weak subatomic physics spontaneous symmetry breaking interactions in the Standard Model 1956 1960 1961 1964 1967–1968 1973 Yoichiro Nambu Several physicists propose that Studies at CERN, describes how broken symmetry breaking gives rise to Geneva provide the first symmetry can occur a particle that provides mass to experimental evidence spontaneously at the all other particles — later to support the Standard subatomic level known as the Higgs boson Model Timeline: Milestones for the 2008 Nobel Laureate in Physics, Yoichiro Nambu. 2 PHYSICS Copyright © Nobel Web AB 2008. Nobelprize.org, Nobel Prize and the Nobel Prize medal design mark are registered trademarks of the Nobel Foundation. 2008 NOBEL LAUREATES the time was insufficient to explain the observed behaviours, and predicted the existence of as yet ibrary undiscovered elementary particles. It did not, how- L ever, specify precisely what form these particles hoto should take. Kobayashi and Maskawa hypothesized P the existence of a third family of quarks, which are CIENCE some of the building blocks from which all matter K/S and antimatter are formed. They then had to wait ARLIC almost three decades for the experimental results G that would fully verify their hypothesis. The existence ARK of all three families was finally confirmed when the M last member was observed in the mid 1990s. Symmetry breaking in particle physics continues to be the focus of intense speculation and investigation. One of the most infamous examples of symmetry breaking, the particle or set of particles known as the Higgs boson, thought to be responsible for breaking the symmetry between electromagnetism and the so-called weak nuclear force, could help solve one of the greatest outstanding questions in physics – how particles acquire mass. Whether or not this mysterious particle exists will be the main subject of scrutiny at the Large Hadron Collider, the giant particle accelerator soon to go into operation outside Geneva, Switzerland. James Cronin and Val Fitch experimentally detect a new Charm quark discovered at First quark of the third violation in the symmetry Stanford Linear Accelerator family, the bottom laws in a subatomic particle Center, USA, and CERN, quark, discovered at known as a kaon Geneva, Switzerland Fermilab, USA 1964 1973 1974 1975 1977 1994 Kobayashi and Maskawa publish their Martin Perl discovers Top quark model proposing why symmetry is broken the first new member discovered in subatomic particles, and predict the of the third family: at Fermilab existence of a third family of quarks the tau lepton Timeline: Milestones for the 2008 Nobel Laureates in Physics, Makoto Kobayashi and Toshihide Maskawa. PHYSICS 3 Copyright © Nobel Web AB 2008. Nobelprize.org, Nobel Prize and the Nobel Prize medal design mark are registered trademarks of the Nobel Foundation. 2008 NOBEL LAUREATES In his own words: Yoichiro Nambu y his own admission the concept that Yoichiro Nambu devised in the early 1960s — that hicago of spontaneous broken symmetry in particle C OF B physics — is “a bit difficult to explain” in simple terms. But while lecturing the day before he had been awarded the Nobel Prize in Physics, Nambu NIVERSITY chanced upon an elegant analogy to describe how U HE such broken symmetry can occur spontaneously. /T RANE G “I saw a roomful of people all looking towards me E and I thought that’s strange, why do they look only D in one direction?” But if one person in that crowd loyd L turns their head and looks in the opposite direction then of course people nearby will turn around to Yoichiro Nambu at the University of Chicago. see what that person is looking at. “So there is a kind of wave propagating from that person. And that is the wave associated with broken symmetry.” Nambu eventually joined his group, and thanks Having begun his career as a theoretical physicist to Tomonaga’s recommendation Nambu was able in Japan during the Second World War, Nambu to get a job first in Japan and then at Robert is no stranger to looking for explanations in the Oppenheimer’s Institute at Princeton University. midst of turmoil. Nambu describes being “lucky The few years he originally planned to spend in enough” to get a research position at the University America would become a lifetime. “I was not able to of Tokyo after the war, though he was working do good research to my satisfaction while I was in under conditions that are a world away from the Princeton, so I wanted to stay for a few more years conditions enjoyed by most physicists nowadays. in America before going back to Japan.” Fortunately “I spent two, three years sleeping in my office, Nambu was able to get a postdoctoral position at shared with maybe eight or so people. Everyday I the world-renowned Physics Department at the had to go shopping, and sleep on my desk.” But the University of Chicago. “I jumped at the opportunity! bleak conditions did provide one huge advantage, I came here and I have stayed here ever since.” says Nambu: “I kept thinking about physics.” All of which illustrates the virtues of being in the By good fortune, a student of Sin-Itiro Tomonaga, right place at the right time, and Nambu feels who would receive the Nobel Prize in Physics in grateful to have been a theoretical physicist at the 1965, happened to be working at the neighbouring time he began his research. “I was very fortunate. desk. By discovering what Tomonaga was doing Particle physics was created in the early 1930s. Ernest Lawrence invented the cyclotron on the one hand, and [Hideki] Yukawa in Japan invented “If one person in that crowd particle physics, the theoretical side, and they went turns their head and looks in along side by side.” the opposite direction then When asked whether young physicists should follow of course people nearby will his example and only eat and think about physics, Nambu laughs. “Yes! That’s a very good thing! turn around to see what that My whole career was formed by the three years I person is looking at” was in Tokyo.” This article is based on a telephone interview with Yoichiro Nambu following the announcement of the 2008 Nobel Prize in Physics. To listen to the interview in full, visit http://nobelprize.org/nobel_prizes/physics/laureates/2008/nambu-interview.html 4 PHYSICS Copyright © Nobel Web AB 2008. Nobelprize.org, Nobel Prize and the Nobel Prize medal design mark are registered trademarks of the Nobel Foundation. 2008 NOBEL LAUREATES In his own words: Makoto Kobayashi hen recalling the groundbreaking theory predicted that there had to be one more. he developed with Toshihide Maskawa “At first we were not confident about this six quarks Wthat has been rewarded with the 2008 scheme, but gradually we came to believe that this Nobel Prize in Physics, Makoto Kobayashi reveals actually is the case.” a refreshing degree of honesty.