C12 Report

C12 Report

Report to the 2002 General Assembly for 2000-02
Berlin, Germany
October 7-12, 2002

Officers 2000-2002

Chairman: B. Frois, France
Vice-Chairman: E. M. Henley, USA
Secretary: A. W. Thomas, Australia

J. Äystö, Finland S. T. Belyaev, Russia
I.-T. Cheon, Korea E. Fiorini, Italy
B. Jonson, Sweden S. Nagamiya, Japan
P. Kienle, Germany Z-X. Sun China
L. Schaller, Switzerland W. T. H. van Oers, Canada

Associate Members:
J. Burgdörfer, Austria ( Member of C 15 )
W. Gudowsky, Sweden, ( IUPAP delegate for SCOPE )
P.I.P. Kalmus, United Kingdom, (Chairman of C 11 )

Council Liaison Member : B. Richter, USA

The General Aims of the Commission are to:

  • Promote the exchange of information and views among the members of the international community of physicists in the field of Nuclear Physics.
  • Recommend for IUPAP sponsorship, international conferences, symposia and seminars, which qualify for support under Union regulations.
  • Maintain liaison with other Commissions

The work of the Commission is carried out at meetings and by correspondence. The annual meetings are scheduled during conferences sponsored by the C.12 Commission. Williamsburg (1996), Seattle (1997), Paris (1998), Uppsala (1999), Strasbourg (2000), Berkeley (2001), Munich (2002). Participation by members remains at high level.

Conferences Sponsored by the Commission

2000 16th International Conference on Few Body Physics, Taipei, Taiwan
2000 3rd International Symposium on Symmetries in Subatomic Physics, Adelaide, Australia
2000 14th International Spin Physics Symposium (SPIN2000), Osaka, Japan
2000 7th International Conference on Nucleus-Nucleus Collisions, Strasbourg, France

2001 International Nuclear Physics Conference (INPC2001), Berkeley, CA, USA
2001 3rd International Conference on Exotic Nuclei and Atomic Masses, Hameenlinna, Finland
2001 16th International Conference on Cyclotrons and their Applications, East Lansing, MI, USA

2002 International Conference on Particles and Nuclei (PANIC02), Osaka, Japan
2002 20th International Conference on Neutrino Physics and Astrophysics, Munich, Germany
2002 11th Conference on Physics of Highly Charged Ions (HCI-2002), Caen, France

The proposal to hold the next International Conference on Nuclear Physics (2004) in Göteborg (Sweden) has been approved by the C12 Commission.

The goal of nuclear physics is to understand the properties of hadronic systems, including nuclear matter, atomic nuclei and how nuclei are built up from elementary constituents. Nuclear physics involves the study of diverse phenomena at vastly different scales, from the interaction of elementary entities (quarks and gluons) inside nucleons or nuclei, to the formation of elements via nuclear synthesis in stars and supernovae, or the characteristics of hot, dense nuclear matter as it occurred in the early Universe.

The fundamental issues of Nuclear Physics have evolved in the past few years and can be summarized as follows:

  • What are the constituents of matter, how do they interact, and how do they form hadrons and nuclei?
  • What are the limits of nuclear stability?
  • What happens to matter at extreme pressures and temperatures?
  • What is the origin of the chemical elements in the cosmos?
    In the last few years a number of experimental results have been obtained and large new facilities have been completed or are now being planned to answer to these fundamental questions. The most significant results and projects are summarized below.

Electromagnetic structure of the nucleon

A highly active community is currently performing electron-nucleus scattering experiments at facilities around the world. Advances in techniques using polarized electrons yielded a wealth of data on the nucleon form factors. A major success of the field is the availability of high-energy electron beams with both high intensity and high polarization (>70%) now routinely available. An extensive research program on the electromagnetic structure of the proton and neutron form factors using polarization techniques is in progress. The experiments have achieved an unprecedented level of precision. A striking example is the wealth of new data obtained at the Thomas Jefferson National Accelerator Facility (TJNAF) in the United States using the three, simultaneous 6 GeV beams.

  • Until recently, the charge and magnetization distributions in the proton were assumed to be proportional to one another (corresponding to µGe/Gm=1). New data show that this is not true, and is leading to a re-examination of the dynamics governing the proton’s quark wavefunctions.
  • Strange quark-antiquark pairs are constantly bubbling up in the proton. One expects a substantial probability of strange quarks and a corresponding contribution to the charge and magnetization distributions of the proton. To disentangle this contribution from the dominant effects of the u and d quarks requires the use of the weak interaction (Z exchange) as a probe of the strange proton form factor. The HAPPEX experiment has shown that the actual contribution is considerably smaller than expected in most models.

In its recent long-range plan, NSAC has recommended an evolutionary upgrade of TJNAF to 12 GeV, as a priority of the US scientific community.

Nuclear research at the limits of stability and super-heavy elements

One of the questions of current interest is whether or not the role of the magic numbers, well established along the valley of stability, remains important when an extreme excess of protons or neutrons is present in a nucleus.

The doubly-magic nucleus 48Ni was recently observed for the first time at the National Heavy Ion Facility (GANIL) in France] using a high-intensity 58Ni beam at 74.5 MeV/A on a nickel target. It is the only case of a doubly-magic nucleus for which the mirror nucleus, 48Ca, is bound. A lower limit of its half-life of about 0.5 •s and an estimate of the production cross-section around 0.05 pb were deduced.
In the domain of super-heavy element research, the discovery of the element 112 at GSI is confirmed while the existence of elements 114 and 118 remains a question.
Another important experimental result has permitted to confirm the existence of a decay mode that has been actively sought for 40 years by the nuclear physics community. In two very recent experiments, one at GANIL in France and one at GSI in Germany, an international team of physicists has demonstrated that the ground state of the atomic nucleus Iron-45 decays directly by the emission of two protons. For the first time, the results from the experiments at GSI and at GANIL demonstrate that a nucleus with very large proton excess can spontaneously disintegrate by double proton emission from its ground state with a comparatively long half-life, which can therefore be directly measured. This should allow one to study the mechanism of two-proton emission, thus opening up a new way for observing the internal forces governing the atomic nucleus.

Rare isotope beams
First generation Radioactive Nuclear Beam [RNB] facilities are operating or under construction in the three regions of the world where nuclear physics is most actively pursued, Europe, North America and Asia/Pacific. These facilities continue to produce important results, and ambitious experiments are planned with them in the next few years. However, several studies of the projected needs of nuclear physics carried out all around the world have made it quite clear that major breakthroughs towards the ultimate scientific goals will only be achieved by the next generation of RNB facilities.
The GSI laboratory in Germany has presented to the scientific community the conceptual design report of a powerful new accelerator facility generating intense high quality secondary beams, including radioactive nuclei and antiprotons. The new facility will provide beam energies of a factor 15 higher than presently available at GSI for all ions, for protons to uranium. Compared to the present GSI facility, the primary beam intensity will be a factor of 100 higher and a factor 10,000 in secondary radioactive beam intensities. The research program will be focused on the investigation of nuclei far from stability, dense hadronic matter and many-body nuclear physics.

Matter at extreme pressures and temperatures

The quark gluon plasma is a state of matter that is predicted to have existed some 10 microseconds after the occurrence of the Big Bang. Seven different experiments at CERN, in which 33 TeV lead ions crashed into heavy element targets give strong hints of the existence of the quark gluon plasma. But confirmation of the existence of this new phase of matter awaits a new generation of results from the Relativistic-Heavy-Ion-Collider (RHIC) at Brookhaven and the future Large Hadron Collider at CERN. RHIC has now attained full energy with 100 GeV Gold ions colliding with 100 GeV Gold ions. The first experimental results were presented at INPC2001 in Berkeley.

Beginning in 2005, part of the experimental program of the CERN Large Hadron Collider (LHC) will be devoted to the study of nuclear collisions in the special-purpose ALICE detector, at energies some thirty times higher than RHIC.

Nuclear Astrophysics

The most exciting results are the recent observations from the Sudbury Neutrino Observatory (SNO) in Canada. This laboratory, funded for a large part by the nuclear physics community, uses a considerable amount of heavy water to interact with cosmic neutrinos. The results have solved the mystery of the missing solar neutrinos, a puzzle for solar theory for more than 30 years. The results confirm that solar models are correct but give evidence that neutrinos decay and oscillate in their journey to the earth. Neutrinos transform from electron-neutrinos to muon- and/or tau-neutrinos. The flux of electron-neutrinos, measured in the charge current interaction e + d —>p + p + e-, together with earlier results from Super-Kamiokande on the neutrino elastic scattering flux (encompassing all three neutrino types) x + e- —> x + e- show that there is a non-electron type, active neutrino component in the solar flux. The total flux of active 8B neutrinos that can be so deduced is in excellent agreement with the predictions of solar models.

JAERI-KEK Joint Project

Japan has decided to build a major 50 GeV and 1 MW multipurpose proton facility. Several beams, including intense kaon beams, will be available for particle and nuclear physics. This should allow the study of strange hypernuclei to be pushed into new regions. Intense neutrino beams directed towards the Super-Kamiokande detector will allow one to study new features of neutrino oscillation. Finally, neutron physics and transmutation of nuclear wastes (see below for more detail) will be also important parts of the research program.

Nuclear Theory

A major development in nuclear theory is the considerable progress in lattice QCD that has been made recently and which is promised for the next few years. Developments in improved quark and gluon actions have increased to lattice spacing that one can use while still obtaining accurate continuum results. Funding agencies in Europe and the USA have agreed to support a number of dedicated High Performance Computers, all at the level of 10 Teraflops or thereabouts. These machines should permit full QCD simulations at quark masses only a factor of 3 or 4 above the physical light quark masses. The combination of improved chiral extrapolation and the new generation of supercomputers means that we can look to lattice QCD producing accurate hadron properties at the physical quark masses within the next five years.

Three vigorous nuclear theory centers, INT at the University of Washington in Seattle (USA), ECT* at Trento (Italy) in Europe and CSSM at Adelaide (Australia), have each year an extensive program of workshops with a large international participation from all over the world. Specific programs are devoted to interdisciplinary topics. These centers continue to thrive and stimulate closer interaction between theorists around the world as well as between theorists and their experimental colleagues.

Nuclear Energy Research

Nuclear fission is one of the few large-scale carbon-free energy sources and currently provides 7% of global primary energy (17% of electricity) without any CO2 waste. Its costs are now well known and are unaffected by increases in oil and gas prices. It supplies 35% of the electricity generated in Europe, i.e., 75% of its CO2?free power.

Nuclear power does produce radioactive wastes. However, the short-lived wastes from operations are already disposed of safely in many countries. Comprehensive research for decades has led to a common view among international experts that the “knowledge and technology exist” for safe waste management, ready to be used by society. The final disposal of the long?lived waste is not yet industrially implemented, but demonstrations are under way in several countries.

Today, overall, only 4% of the initial quantity of fuel is consumed in a reactor, i.e., less than 1% of the quantity of natural uranium needed for the production of enriched uranium. The spent fuels removed from the reactors contain 95% of uranium, 1% of plutonium and 4% of fission products. Only fission products constitute waste. Uranium and plutonium can be re-used to produce energy. With the dual aim of economizing natural resources and optimizing waste management, some countries, such as France, process the spent fuel to separate the energy-yielding materials from the waste. The recycled uranium is stored with the prospect of its use at a later date in fast breeder reactors, and the plutonium is recycled in today’s reactors in the form of MOX fuel, a mix of uranium and plutonium. If the use of nuclear energy is to be greatly expanded to reduce man-made greenhouse gases, some such system will be needed.

To continue the development of nuclear energy, we must provide effective and acceptable technical solutions for the long-term management of the radioactive wastes produced by current reactors; solutions do exist and could be gradually implemented. Studies are underway on multiple recycling of plutonium in power reactors, thus destroying it and leaving the fission fragments and minor actinides for geological storage. Also under study are transmutation systems which convert the long-lived component of spent fuel to a form only requiring isolation for on the order of hundreds of years to a thousand years — a time span of already existing man-made structures.

Preparation for the future sustainable development of nuclear energy will involve a new generation of nuclear power generation systems, in an inclusive approach covering all the aspects of the reactor and fuel cycle. The “Generation IV” international initiative (Europe, United States, Japan, Russia, etc.), aims to develop, for deployment around 2030, new types of nuclear reactors which are simpler, completely free from core-meltdown, and competitive with the best fossil-fired plants, as well as fuel cycles more resistant to proliferation. Comprehensive assessment studies have already demonstrated that these objectives are achievable.

Globally, the processing of spent fuels, the consumption of the plutonium in light water reactors, and the transmutation of long-life radiotoxic wastes (minor actinides) in the new generation reactors, could reduce the long-life radiotoxicity of the waste by a factor of 100, leaving a residual radioactivity that would then be comparable to that of the initial natural uranium after several hundred years.

Innovative nuclear energy research is of paramount importance to develop improved designs, maintain and renew expertise, whilst continuing to build competence in operation and decommissioning of the present generation of reactors.

Cancer therapy with nuclear beams

The goal of radiation therapy is to maximize the tumor dose without harming surrounding healthy tissues. The use of heavy particles in radiotherapy is motivated by a superior accuracy in the spatial dose distribution in the human body for deep seated tumors compared to photons and electrons, and an inverse dose profile depositing the highest dose at the end of the particle range in the tumor volume.

For proton therapy, the needed accelerators are, at present, industrial products, while optimized medical synchrotrons for light ion therapy have recently been designed by CERN and GSI. Active beam delivery systems using magnetic beam deflection and energy variation by the accelerator have recently been developed, and have been put into operation at PSI (Switzerland) for protons, and at GSI (Germany) for carbon beams.

Using positron emission tomography (PET), the small amounts of positron-emitting isotopes created by the carbon beam can be used to determine the exact beam location inside the patient’s body. The new techniques of more accurate beam delivery and precise control permit the treatment of tumors in critical locations such as the brain, or the vicinity of the spinal cord.

Nuclear Physics News

“Nuclear Physics News International”, the journal edited by the Nuclear Physics European Coordination Committee (NuPECC) of the European Science Foundation, regularly provides information on the status, new directions and opportunities of nuclear science all over the world and can be accessed at http://www.nupecc.org/.

Frois and A. Thomas