NATIONAL SCIENCE FOUNDATION
TOKYO REGIONAL OFFICE

October 23, 2001

The National Science Foundation's Tokyo Regional Office periodically reports on developments in Japan that are related to the Foundation's mission. It also provides occasional reports on developments in other East Asian countries.

Tokyo Office Report Memoranda are intended to provide information for the use of NSF program officers and policy makers; they are not statements of NSF policy.

Japan’s High Energy Accelerator Research Organization (KEK), located in Tsukuba, and the high-energy community in Japan conduct world-class fundamental research. Some of their recent achievements have hit the front page of the scientific news, like the first evidence for neutrino oscillation by SuperKamiokande and now confirmed by the K2K experiment at KEK, or the CP violation measurement in B mesons at BELLE. On June 2001, KEK set the world record for the highest luminosity ever achieved at a collider beam facility.

With a 33 Billion Yen (ca. $260 Million) annual budget and 735 staff members, KEK is one of the five major laboratories in the world pursuing fundamental research on the nature of the basic forces and on the understanding of the early universe.

Technological applications based on accelerator developments have generated numerous projects: making use of synchrotron radiation or neutrons, or tackling nuclear waste transmutation, or fusion ignition. KEK offers a full range of accelerator facilities: 21 synchrotron radiation lines in the photon factory complex, a neutron spallation source and a high flux proton synchrotron (PS). A more energetic PS has recently been approved by the Diet and will be built in a KEK/JAERI (Japan Atomic Energy Research Institute) collaboration close to JAERI’s Tokai site. The tremendous impact of accelerator research on all fields of basic research and on technology developments would by themselves justify the large investment necessary for this research.

KEK’s next big proposed project is the Japan Linear Collider project (JLC) to address the basic question of the mass generation mechanism through the search and study of the Higgs boson. A lot of progress has been made at the Accelerator Test Facility (ATF) to demonstrate the feasibility of the JLC design prefered by KEK and the Stanford Linear Accelerator Center (SLAC)..

The development of an X-ray Free Electron Laser (XFEL) based on the JLC technology will revolutionize virtually all research fields thanks to an eight order of magnitude increase in the brilliance and sub-femtosecond time resolutions.

A strong competition is building up between the four major sites for hosting the next linear collider. Japan and the Asian countries represented in the Asian Committee for Future Accelerators (ACFA) is likely to propose a regional center to host the global internationally operated and managed accelerator. ACFA members rely on Japan to launch such an initiative as quoted from its September 2001 statement

”ACFA would be happy if the Japanese Government would take the initiative in creating such an international organization”.

This clearly emphasize that the final decision will be political. A decision in favor of siting the next collider in Japan would promote Asia as a front-runner of the most high-tech as well as fundamental research program ever.

Organization of KEK Japan’s High Energy Accelerator Research Organization (Ko Enerugi Kasokuki Kenkyu Kiko, or KEK: http://www.kek.jp ) was established in April 1997, by merging three closely related laboratories: the National Laboratory for High Energy Physics, the Institute for Nuclear Studies (University of Tokyo) and the Meson Science Laboratory (University of Tokyo). The new organization is mostly integrated in the site of the former National Laboratory for High Energy Physics in Tsukuba. It houses two institutes: the Institute of Particle and Nuclear Study and the Institute of Materials Structure Science. In addition, the Accelerator and Applied Research Laboratories, the Engineering Department and the Administration Bureau are attached directly to the director General of KEK.

In fiscal year 2001, KEK staff amounts to 735 people (400 Research Scientists, 209 Technical Engineering and 126 Administrative staff). Its budget is 33 Billion Yen ($260 Million), including 6.4 Billion Yen for salaries.

Although KEK is the single laboratory dedicated to high energy physics in Japan, it maintains strong connections with a much wider community scattered in many universities and institutes in the country, including RIKEN, ICEPP and ICRR (University of Tokyo), Kyoto, Tohoku and Hiroshima University (For a more complete list see http://www.kek.jp/hep/ ) Other organizations involved in similar research in the world with which KEK has very strong ties, are:

• CERN: the European Center for nuclear research, Geneva with LEP (e+e-) and LHC (pp, ions-ions)
• DESY laboratory in Hamburg (Germany) with PETRA ( e+e-) and HERA (ep)
• FermiLab (IL, US), with the TEVATRON (pp)
• SLAC: Stanford Linear Accelerator Center, Palo Alto, CA US, LC (e+e-)

High-energy physics or particle physics is the study of the ultimate components of matter and the understanding of the fundamental forces of nature. When two high energy beams of particles (e.g., electrons (e-), positrons (e+), protons (p), ions (like Pb)) are collide at high energies, the interaction of particles in each beam may produce a so-called “event”. The precise study of those events gives information on the fundamental forces at the quantum level: the electro-weak force and the strong force. By going to very high energy, one reproduces in laboratory, the type of collisions that were taking place in our universe just after the Big Bang. The higher the energy the closer in time to the beginning of the universe, one can probe. One can therefore reproduce in the controlled environment of the lab, the exact energetic conditions that existed at each period of the creation of the universe. It is therefore not surprising that high-energy physics and cosmology have become quite related and have led to the new buzzword?astro-particles?referring to the search for the hypothetical particles produced in the very early universe.

This briefly summarizes the fundamental aspect of high energy physics as a search for knowledge. But there is another side to the coin. The development of the extremely sophisticated hardware and software needed to produce those high energy beams as well as the complex development of the particle detectors and experiments and the analysis of their results have found numerous applications in many other research fields. Synchrotron radiation (higher energy X-rays), an unwanted by-product of any beams accelerated in devices with circular configuration, has become a fantastic tool to study, at the atomic level, biology samples like protein structures, material defects, crystals, for example. Neutron beams produced by colliding protons on nuclear targets (so-called pulsed spallation sources) gives complementary information on materials at the nuclear level. Proton beams are also used for cancer therapy and very intense proton beams are being developed for nuclear waste transmutation or as an ignition procedure for inertial fusion. Beam can also be used to predict the physics within, and effects of, a nuclear blast. Beam irradiation can provide a safe way for food products conservation. Most of the big hospitals, nowadays, have accelerators to produce short-lived isotopes for diagnostic purposes. The need to control those big experiments and to analyze the produced data has led to the development of sophisticated documentation retrieval that led in turn to the development of the world wide web.

The KEKB Accelerator (B-Factory) and the Tsukuba Experimental Hall BELLE experiment: KEK’s TRISTAN Collider has been refurbished to provide a state of the art asymmetric e⁺e^- beam system ready for CP violation measurements in B meson decay in the BELLE experiment. Pairs of B mesons and their anti-particles are produced. By measuring the life-time (or the rate of decay) of these short-lived particles (just over a trillionth of a second) and anti-particles one can check if a B meson particle is the exact symmetric or mirror image of its anti-particle. If not CP conservation (the product of two transformations Charge conjugation and Parity) which is equivalent to time reversal is violated leading to a small asymmetry between matter and anti-matter. This small difference may be part of the reason why our universe is made of matter and not of anti-matter, although this is probably not the full story as both matter and anti-matter should have been produced in equal quantities in the early universe. The first results show, as also seen in a similar experiment running at SLAC (BaBar experiment), that such a violation exists. More data taking is necessary to have more precise results, as the SLAC and KEK results do not fully agree. It is worth mentioning that the KEKB accelerator provides better beam conditions (higher luminosity) than the SLAC counterpart. On June 2001, it achieved the world record for the highest luminosity ever achieved at a collider beam facility. This will enable the Japanese experiments to provide more accurate results.

Neutrino Facility and the K2K (KEK to(w) Kamiokande) experiment: A neutrino is a neutral particle that experiences only the weak force. It is produced in large quantities in nuclear reactors. Low energy neutrinos go through the earth almost without interacting. Among two million neutrinos traversing the 250 kilometers of rocks of the earth surface, only one may interact. For the first time the SuperKamiokande team in the deep underground experiment in the Kamioka mine close to Toyama have shown that the neutrinos produced in the earth’s atmosphere by highly energetic primary cosmic particles were experiencing oscillations (the periodic transformation to a similar neutrino but associated with another lepton). More recently the SNO experiment (Canada) has brilliantly confirmed this result and by combining the results with SK have set a mass range for active neutrinos between 0.05 and 8.4 eV. Measuring the neutrino’s mass is a result that had been sought for many years without success. A massive neutrino can have major consequences for the search of the so-called dark matter responsible for most of the mass of the universe. To check and measure this effect in more detailed, a neutrino beam produced by the 12 GeV proton synchrotron at KEK has been directed to SuperKamiokande, 250 km away from Tsukuba for the so-called long baseline oscillation experiment. The first measurement confirms the SuperKamiokande discovery. But more data taking is necessary to obtain more precise results. Similar experiments are being planned between CERN and Gran-Sasso (OPERA) and in the US between Fermilab and the Soudan mine (MINOS) experiments. KEK’s proposed new project for a high intensity proton collider capable of energies up to 50 GeV (JHF for Japan Hadron Facility) accepted by the Diet this year to be built at the Tokai laboratory of JAERI (Japan Atomic Energy Research Center) in collaboration with KEK will provide a more intense neutrino beam and will yield a high precision measurement of the neutrino mass.

The JAERI/KEK JHF program will have many other goals than producing neutrinos. It will open new energy and intensity windows for the study of short lived nuclei (super-heavy elements and astrophysics), for neutron science, for muon science and for nuclear transmutation linked with the nuclear waste management.

The Photon Factory is part of the IMSS: Institute of Material Structure Science. This specific synchrotron ring has been constructed to provide 21 beam lines, on which up to three simultaneous experiments can take place. Thirty-three experimental stations are devoted to hard X-rays experiments, 18 beam lines provide soft X-rays or Vacuum Ultra Violet (VUV) radiation. On average 500 experiments are performed each year. Over 2,000 publications have been produced between 1996 and 2000 in material science and condensed matter physics, in biological science, chemical, structure of surface and interface, crystallography, as well as in medical application. This technology is becoming so powerful that most countries in the world have constructed this type of facility for their domestic use. For example, in Europe the ESRF in Grenoble and the “Soleil Project” in Paris. A similar facility exists in Daresbury in the UK, and in the United States at Lawrence Berkeley Laboratory, Argonne, and Cornell. The future of this technology is the X-ray Free electron laser, as will be mentioned later on.

The ATF (Accelerator Test Facility) and the JLC project: Linear Colliders have become the spearhead of high-energy physics for the “after LHC” research era. (The LHC, or Large Hadron Collider, is the proton-proton collider currently being constructed at CERN in Geneva, which is scheduled to become operational in 2006.) Accelerating electrons above 100 GeV achieved in the 27 km circumference ring of the former LEP collider at CERN by means of a circularly configured accelerator is not feasible, since large amounts of energy are lost by the circulating beam in the form of synchrotron radiation. Achieving higher energies requires a linear acceleration scheme. The proposed KEK project involves a 25 km long underground machine consisting of two opposite linear accelerators, one for accelerating electrons and the other for positrons, providing a 500 GeV colliding energy. In principle, the energy could be increased up to 1.5 TeV in a second phase. This would open a brand new energy research field where theorists expect many new discoveries to be made.

As has been convincingly demonstrated by the high precision experiments done at CERN’s former LEP collider, high-energy physics is almost perfectly described by the so-called “Standard Model” which unifies two of the four fundamental forces of the universe, the electro-magnetic and the weak forces. The former is responsible for all the electric and magnetic phenomena so much used in our everyday life, and the latter is manifested in the decay of many elementary particles and unstable nuclei. The two other forces that remain to be unified are the strong force that bind together the quarks inside the proton and neutron, and gravity which is the long-range force acting between the sun and planets and between stellar and galactic objects, for example. The Standard Model shows that the electro-magnetic force carried out by the massless photon and the weak force acting through one of the three heavy Z/W bosons are issued from a unique force called electro-weak. However, the theory fails to explain why the photon and the Z/W bosons are so different in mass, unless a mechanism conjectured by Peter Higgs is at work. This would explain not only the mass difference between the photon and the Z/W bosons, but also all particle masses in the universe, including every day matter. This mechanism should be mediated through a new particle called the Higgs boson.

The study of this hypothetical particle is the major “raison d’etre” of the proposed KEK linear collider, along with a precise study of the top quark recently discovered at Fermilab and of the many particles that may appear if the Higgs is found, as conjectured by the supersymmetry models.

The possibility of constructing such a collider has attracted world wide attention. Four pilot projects are being developed: At SLAC, DESY, CERN and KEK. These are based essentially on three different technologies. The SLAC and KEK projects propose high power C or X-band tuned accelerating conventional structures. The DESY TESLA design is based on superconducting cavities and the CERN CLIC uses a more advanced but less tested technique using a low energy but intense secondary beam. All technologies have their pros and cons, but the SLAC/KEK projects should be better suited for reaching higher energies.

Considerable progress has been made at KEK’s Accelerator Test Facility in reducing the emittance of accelerated beams in order to produce the nanometric beams necessary to design a high luminosity machine.

A revolutionary new tool is hidden in the luggage of this big science project: the X-ray Free Electron Laser. Based on the technology developed for the linear colliders, this new device should be capable of producing the same sort of giant step in the x-ray region that the electronic microscope has provided to the optical region of the electromagnetic spectrum. The coherent high-energy X-rays produced would provide up to an eight order of magnitude increase in the peak brilliance and time resolution in the sub-femtosecond range. Energy and spatial resolution will also be tremendously increased. It will for example offer the possibility of “seeing” the dynamics of a chemical reaction that is to say to “see” how the molecules interact with one another. It will offer the possibility of investigating molecular structures without the need for crystallization. It will make possible the study of non-linear interaction of X-rays with matter leading to yet unobserved phenomena like multi-photon processes in atoms and molecules. But even more important by focusing X-rays on volumes with dimensions in the sub micron range, plasmas could be generated at temperatures and pressures yet unexplored.

The linear collider projects are therefore fundamental research programs with the potential for the development of new fascinating tools that will have an impact on many other research fields at the fundamental, the applied, and the industrial level. A strong competition is underway among countries to be selected to host this new machine. The price tag would be high: between $4 billion and $6 billion. KEK and the Japanese high-energy physics Japanese community have proved that they have reached a level of expertise required to build such a facility.

A group of Asian countries whose potential growth is enormous are getting together in the so-called Asian Committee for Future Accelerators (ACFA^[1]) to ascertain the implication of this worldwide big science policy for the region. The technological and economic implications of this fundamental project are so important for the future that no country can afford to remain behind or become a spectator of this new undertaking.

If backed up by their respective funding agencies, Japan and other Asian countries could propose to adopt the principle of a global laboratory, where only the minimum but mandatory support is provided, locally, on the accelerator site. All other activities such as computer support, manufacturing or assembly lines, documentation management, program administration, in addition to the data analysis and simulation which are already usually performed outside of the big centers would be de centralized and dispersed to other regions or countries. This would create a network of relationships between the Asian countries that would play an important role not only at the scientific level at large but also at the political level. CERN, in Europe, played a similar role when the Europe Union was in its infancy. In addition, the prospect of building one or several (in the coming 20 years) X-ray free electron laser systems, based on the linear collider technology in other Asian countries than the one hosting the so-called Next Linear Collider would be a strong incentive to foster, on practical grounds, this new High Energy Physics Asian Community. Other committees in the world are discussing the site selection: ECFA (Europe), HEPAP (US) and ICFA (Worldwide) whose chairman is Prof. H. Sugawara, Director-General of KEK. The final decision will be essentially a governmental decision as whatever the internationalization level will be, a large fraction of the total cost will have to be borne by the host country. This project is seen by the Asian community as a unique possibility to become a front-runner in the most high-tech as well as the most fundamental research program ever.

[1]  The Asian Committee for Future Accelerators currently includes representatives from: China, India, Indonesia, Pakistan, Japan, Vietnam, Thailand, Korea, Taiwan, Malaysia and Australia.