Perspectives in Heavy Ion Physics

The following sections are included:

• PREFACE

• LIST OF COMMITTEES

• GREETING MESSAGE OF ITALIAN AMBASSADOR

• CONTENTS

No abstract received.

I address in my talk the following problems which are raised by recent radioactive ion beam (RIB) experiments,

1. Decoupling and screening effects of the neutron skin on shell model effective charges.

2. Dynamical effect beyond mean field theory and new magic numbers

3. Melting of shell gaps at the magic numbers N=20 and N=50 and strong E3

Recent results obtained, often in fruitful collaboration with Japanese collegues, in the study of the interplay between single-particle and collective degrees of freedom in exotic nuclei are reviewed.

Coulomb dissociation of halo nuclei has been investigated as a spectroscopic tool. Substantially large B(E1) strength at low excitation energies appeared in the Coulomb dissociation of halo nuclei is shown to be sensitive exclusively to the halo wave function, thereby enabling us to extract the spectroscopic factor for the halo configuration. We first review the classical case on ¹¹Be and show the results on the application to the neutron-rich ¹⁹C nucleus. We have recently made a further investigation on the Coulomb dissociation, such as higher order effects and nuclear breakup contaminants, by using the impact parameter analysis of the reaction on the new data set of ¹¹Be with higher statistics. It shows that such effects are small, and that the use of data with large impact parameter enables us to obtain more precise spectroscopic information.

Proton-knockout (p,2p) reactions from RI beams on a hydrogen target have been studied at incident energies between 70 and 250 AMeV. Reactions from proton-rich nuclei, p(⁹C,2p)⁸B and p(¹⁷Ne,2p)¹⁵Op, were performed for studying the single-particle properties of weakly-bound valence proton(s) in proton-rich nuclei. Reactions from neutron-rich nuclei, p(⁶He,2p) and p(¹¹Be,2p), were performed to produce exotic resonances, ⁵H and ¹⁰Li, beyond the drip line.

The disappearance and the appearance of the magic numbers in N ~ 20 unstable nuclei are discussed with large-scale shell-model calculations, most of which are the Monte Carlo shell model (MCSM) calculations. The MCSM calculations turn out to give a systematic description for this region. The origin of the shift of the magic structure from N = 16 to 20 is shown to be the spin-isospin dependence of the nucleon-nucleon interaction giving rise to strongly attractive T = 0 monopole interaction between the 0d_5/2 and the 0d_3/2. The extreme location of fluorine drip line can be understood from the viewpoint of the varying N = 20 shell gap.

Experimental search for ⁵H using secondary beam of ⁶He has been performed. The transfer reaction p(⁶He, ²He)⁵H was studied by detecting two protons emitted from the decay of ²He. A peak consistent with the ⁵H resonance at 1.7 – 0.3 MeV above the n+n+t threshold was observed, with a width of 1.9 – 0.4 MeV. The angular distribution of the p(⁶He, ²He)⁵H reaction was measured as well as the energy correlation of two protons.

The structure of C isotopes are investigated using a microscopic α+α+α+n+n·· model based on the molecular orbit (MO) model. The stability of the linear-chain of 3α with respect to the breathing mode and the bending mode for various neutron configurations is investigated. The combination of the valence neutrons in the π- and the σ-orbit is promising to stabilize for these modes, and the excited states of ¹⁶C with the configuration for the four valence neutrons is one of the most promising candidates for such structure. Furthermore, the equilateral-triangular shape of 3α surrounded by valence neutrons is suggested for ¹⁴C. The 3⁻, 4⁻, and 5⁻ states of this rotational band appear around the ¹⁰Be+α threshold, and these calculated states correspond to the experimentally observed 3⁻ state (9.80 MeV) and 4⁻ state (11.67 MeV). A positive-parity rotational band (0⁺, 2⁺, 4⁺) also arises around this threshold energy, and these results suggest that the picture of inversion doublet structure works also in neutron-rich nuclei.

The absorbing boundary condition approach allows us to treat a few-body scattering problem without discretizing the continuum states. Therefore it is a simple and useful method for describing scattering of weakly bound nuclei, where the breakup process plays an important role. We first demonstrate that the absorbing boundary condition method can provide almost the same results as the continuum discretized coupled channel method by taking deuteron-induced scattering as an example. We next apply the absorbing boundary condition method to scattering of single-neutron halo nucleus, ¹¹Be, and discuss the validity of the eikonal approximation.

Based on the β-NMR method on spin-polarized radioactive-isotope beams, magnetic moments of the ground state of light unstable nuclei have been measured. In this paper, we report on a recent result obtained in the g-factor measurement for the ¹⁷C ground state. In the case of ¹⁷C, the g-factor is extremely sensitive to whether the spin-parity is 1/2⁺ or 3/2⁺, which are possible candidates for the ground state: the corresponding Schmidt values, g _s1/2 =− 3.83 and g_d3/2=+0.76, differ largely from each other. Similar observation is gained in more realistic shell model calculations in which g_1/2⁺=−3.13 and g_3/2⁺=−0.58 are predicted. Owing to these large difference, the spin-parity can be reliably assigned from the measurement of g-factor. From the obtained NMR. spectrum, |g(¹⁷C)|=0.5054(24) was determined. This result clearly indicates that the spin-parity for the ground state of ¹⁷C is J^π =3/2⁺.

Recent high precision experimental data for heavy-ion fusion cross sections at energies in the vicinity of the Coulomb barrier systematically show that a strikingly large surface diffuseness parameter for a Woods-Saxon potential is required in order to fit the data. We discuss possible origins for this anomaly, including the effects of dissipation and the sensitivity of fusion cross sections to the choice of inter-nuclear potential. Our study suggests that the frozen density approximation, which is often used in analyses of heavy-ion reactions, may have to be re-examined for heavy-ion fusion.

In this paper we use an eikonal formalism to treat consistently nuclear and Coulomb breakup. Taking the Coulomb potential to first order and the nuclear potential to all orders leads to three terms in the amplitude. One is the standard nuclear term of the eikonal formalism while the other is the same as the Coulomb amplitude of first order time dependent perturbation theory. Furthermore a Coulomb-nuclear coupling term is derived analytically. We calculate the neutron angular and energy distributions and total breakup cross sections. The nuclear-Coulomb coupling gives a small contribution for light targets but it is of the same order of magnitude as nuclear breakup for heavy targets. The overall interference is constructive for light to medium targets and destructive for heavy targets. In the medium energy range interference gives a maximum contribution of about 10% while it tends to disappear at incident energies higher than 100 A.MeV. We suggest that Coulomb breakup experiments should to be analyzed with more accurate models than those used so far.

The dependence of the fusion probability on the orientation of deformed nuclei was investigated for the reactions ^60,64Ni + ¹⁵⁴Sm and ⁷⁶Ge + ¹⁵⁰Nd. Evaporation residues were measured for these reaction systems in the vicinity of the Coulomb barrier and the fusion probability was extracted as a function of bombarding energy. It was found that the fusion probability depends strongly on the orientation of the nuclear deformation. The fusion probability is considerably reduced when the projectiles collide at the tip of the deformed nuclei. On the other hand, when the projectiles collide at the side of the deformed nuclei, the fusion occurs without hindrance. This phenomenon is understood qualitatively by comparing the distance between the mass centers of two colliding nuclei at touching with the position of the saddle point of the compound nucleus. The dependence of the fusion probability on the nuclear shell structure was also investigated for the reactions ⁸²Se + ^134,138Ba, where the nucleus ¹³⁸Ba has a closed neutron shell of N = 82 and the neutron number of the nucleus 134Ba is 78, four less than the closed shell. While the evaporation residue cross-sections for the reaction ⁸²Se + ¹³⁸Ba were well reproduced by statistical model calculations including a subbarrier enhancement of the fusion cross-section, the evaporation residue cross-section for the reaction ⁸²Se + ¹³⁴Ba was about 100 times smaller than those for the fusion reaction ⁸²Se + ¹³⁸Ba. This suggests that the shell closure plays an important role in the fusion process.

A two-step model for fusion of massive systems is proposed for synthesis of the superheavy elements. It enables us to investigate how di-nucleus complex is formed, how the amalgamated system evolves toward the spherical compound nucleus, and then to calculate the fusion probability. Using the calculated fusion probabilities as input data for the statistical decay part of the code HIVAP, we can calculate residue cross sections for the superheavy elements. Preliminary results are given for the system ⁴⁸Ca+²⁴⁴Pu, leading to the element Z=114.

The collision ¹¹⁶Sn + ⁹³Nb at 29.5 AMeV in direct and reverse kinematics has been studied at LNS in Catania. In particular the emission pattern in the ν_perp − ν_par plane of Intermediate Mass Fragments with Z=3-7 (IMF's) shows that for peripheral reactions most of IMF's are emitted at velocities intermediate between those of the projectile- and target-like products. From coulomb trajectory calculations one can infere that these IMF's are produced mainly in the interaction zone, in a short time interval at the end of the target-projectile interaction.

Four topics on nuclear clustering are discussed. The first subject is about the cluster formation in dilute matter which we think is now observed in heavy ion collisions at hundreds MeV/nucleon. The second subject is about our new proposal of the existense of alpha condensed states in light nuclei. Two other subjects are both about the clustering in neutron-rich nuclei. One is the cluster structures in neutron-rich Be and B isotopes. In these isotopes, the clustering prevails as fundamental characters of nuclear structure. The other is the report of our recent study about the possible relation of the clustering with the breaking of the neutron magic number N=20 in ³²Mg and ³⁰Ne.

Multi-nucleon transfer reactions between heavy-ions are analyzed for a variety of system in a semi-classical picture that treat multi-nucleon transfer channels as a succession of single particle transfer. This simple picture describe quite well_neutron pick-up channels up to the +6n channel and the isotopic distribution of the one-proton stripping channel. The more complex channels, that involve the stripping of two or more protons are under predicted. By adding a proton-pair transfer mode (with a macroscopic form factor) a reasonable description is obtained for the isotopic distribution up to the stripping of six protons. The importance of the evaporation in the redistribution of the primordial yields is investigated.

A 4π detection system sensitive to light charged particles is fully operational at the Laboratori Nazionali di Legnaro (LNL) since the end of 1998. The apparatus, called 8πLP, is dedicated to the study of the reaction mechanisms in heavy ion collisions at energies up to 20 AMeV. The system is a telescope array based on ΔE-E, Time of Flight and Pulse Shape Discrimination identification techniques, operating in coinci9595dence with specialized trigger detectors for evaporation residues and fission fragments.

The results obtained in some experiments performed up to now will be presented and discussed.

Results obtained in the frame of CERN SPS heavy ion program by experiments involving italian participation and projects for future experiments are presented. The WA97/NA57 Collaboration observed a strangeness production enhancement measuring Λ, Ξ,Ω. yields in Pb-Pb collisions. NA50 observed a threshold effect in the anomalous charmonium suppression. Both effects are not accounted for in a purely hadronic scenario, while they find a natural explanation in the formation of a deconfmed state of quarks and gluons. The program of experiment NA60, which will probably conclude the CERN SPS activity in the forthcoming years, and of ALICE, which will start data taking in the LHC era, are also highlighted.

Polarized pp collisions at 200 GeV of the center of mass energy will take place for the first time in December 2001, which opens a unique opportunity to study the spin structure of the nucleon and the symmetries in nature. This new field of physics is opened under the treaty between RIKEN and Brookhaven National Laboratory by adding necessary equipments in RHIC, Relativistic Heavy Ion Collider. The physics program with polarized beams at RHIC is overviewed.

Results are presented from the successful year-1 run at BNL-RHIC with Au + Au collisions at . Topics covered are; measurements of charged particle multiplicity and transverse energy, yield ratio of hadrons, transverse hadron spectra, elliptic anisotropy of azimuthal distribution of particles, and hadrons in the high transverse momentum region. The results show interesting new features revealed at RHIC.

We propose the use of the Balescu-Lenard-Vlasov (BLV) equation to describe relativistic heavy ion collisions starting from quark degrees of freedom with colors. We explicitly demonstrate that the Vlasov approach alone is insufficient in the hadronization region. In order to overcome this problem we prepare the initial condition for many events using molecular dynamics with frictional cooling and a Thomas-Fermi approximation to the Fermi motion. These events are averaged and propagated in time using the Vlasov approach. The time evolution of the QGP is discussed.

A pion condensation which might be realized in the neutron stars is a very fascinating phenomenon. The Landau-Migdal parameter representing a short-range correlation in isospin-spin channel is fundamental parameter which determines a critical density ρ_c for the pion condensation. The can be deduced by using a quenching factor of the Gamow-Teller strength in terms of the spin sum rule of S_β⁻ − S_β⁺ = 3(N − Z). Tokyo group has derived the S_β⁻ through the ⁹⁰Zr(p,n) measurement at 300 MeV and deduced the quenching factor of 0.9 which gives rise to and ρ_c ~ 2ρ_ρo. For a reliable estimation of ρ_c, a reduction of the systematic uncertainties regarding the quenching factor is essential. Since large part of systematic uncertainties comes from the S_β⁺, the ⁹⁰Zr(n,p) measurement at 300 MeV has been performed.

Recent observation of the power spectrum of Cosmic Microwave Background Radiation has exhibited that the flat cosmology is most likely. This suggests too large universal baryon-density parameter Ω_bh² ≈ 0.022 ~ 0.030 to accept a theoretical prediction, Ω_bh² ≤ 0.017, in the homogeneous Big-Bang model for primordial nucleosynthesis. Theoretical upper limit arises from the sever constraints on the primordial ⁷Li abundance. We propose two cosmological models in order to resolve the descrepancy; lepton asymmetric Big-Bang nucleosynthesis model, and baryon inhomogeneous Big-Bang nucleosynthesis model. In these cosmological models the nuclear processes are similar to those of the r-process nucleosynthesis in gravitational collapse supernova explosions. Massive stars ≥10M_⊙ culminate their evolution by supernova explosions which are presumed to be the most viable candidate site for the r-process nucleosynthesis. Even in the nucleosynthesis of heavy elements, initial entropy and density at the surface of proto-neutron stars are so high that nuclear statistical equilibrium favors production of abundant light nuclei. In such explosive circumstances many neutron-rich radioactive nuclei of light-to-intermediate mass as well as heavy mass nuclei play the significant roles.

A description is given of the current status of Laboratori Nazionali del Sud, concerning its accelerators and the most relevant detection facilities presently in operation. The main fields of research are also described, concerning both nuclear physics investigation and application of nuclear techniques to different disciplinary fields and some results obtained from recent experiments are illustrated. The programs of development of the laboratory are then presented.

Radiative capture processes in astrophysical hydrogen-burning sometimes involve unstable nuclei. The Coulomb dissociation method has been used to determine the cross sections of such reactions indirectly with intermediate-energy RI beams. Recent studies on reactions in the pp chain, hot pp chain and CNO cycle are discussed.

The underground accelerator facility LUNA installed at the Laboratori Nazionali del Gran Sasso offers unique possibilities for the studies of low cross section nuclear reactions. Using a 50 kV accelerator equipped with a windowless gas target it was possible for the first time to provide a direct measure of the S-factor for the reaction ³He(³He, 2p)⁴He in the energy region of the solar Gamow peak. A new 400 kV accelerator has been installed in the underground laboratories in June 2000. The machine is actually under test in order to proove its capabilities. The new equipment includes also a BGO-4π-summing detector, a data aquisition system FAIR, a windowless gas target system and a beam calorimeter. The work on this equipment is in progress in order to investigate the D(p,γ)³He (old 50 kV accelerator), ¹⁴N(p,γ)¹⁵O (new 400 kV accelerator) nuclear reactions. Screening and stopping power measurements with the two reactions D(³He,p)⁴He and ³He(d,p)⁴He have also been performed at very low energies.

We have measured the nuclear fusion cross section for ³HE(³HE,2P)⁴HE near the solar Gamow peak with a compact accelerator facility OCEAN and with an assembly of counter telescopes with a detection efficiency of 10%. The data obtained at E_cm= 45.3, 43.3, 41.3, 39.3, 37.3, 35.2, 33.1, 31.2 keV improved the existing astro-physical S-factors in statistical and systematic errors. A Monte Carlo simulation program exploiting GEANT3, SRJM and GENBOD computer codes has been developed to estimate the detection efficiency for two proton coincidence with a ΔE-E counter telescopes. The precision of developed program has been investigated by comparing the simulated results with the experimental values for cross section of the D(³He, p)α reaction carried out by replacing the target with deuterium gas. It turned out that the present study involves around 3% systematic errors for an estimation of the detection efficiency. The overall systematic errors for these data from 45.3 to 31.2 keV is 3.8%, that is as good as those of the previous experiments.

Laser-electron MeV photon beams (LEMPBs) developed at AIST have been used for nuclear astrophysics experiments. We present photoneutron cross sections for ¹⁸¹Ta and ⁹Be in conjunction with the origin of the nature's rarest isotope ¹⁸⁰Ta and the nucleosynthesis of ⁹Be in core-collapse supernovae. The present status of developing a LEMPB at SPring-8 is also reported.

We present calculations of r-process nucleosynthesis in neutrino-driven winds from the nascent neutron stars of core-collapse supernovae. A full dynamical reaction network for both the α-rich freezeout and the subsequent r-process is employed. The physical properties of the neutrino-heated ejecta are deduced from a general relativistic model in which spherical symmetry and steady flow are assumed. Our results suggest that proto-neutron stars with a large compaction ratio provide the most robust physical conditions for the r-process. This is due to the short dynamical timescale of material in the wind. Our results have confirmed that the neutrino-driven wind scenario is still a promising site in which to form the solar r-process abundances. However, our best results seem to imply both a rather soft neutron-star equation of state and a massive proto-neutron star which is difficult to achieve with standard core-collapse models. We propose that the most favorable conditions perhaps require that a massive supernova progenitor forms a massive proto-neutron star by accretion after a failed initial neutrino burst.

Research facilities at the RCNP Ring cyclotron laboratory are described. Some topics in physics programs are discussed as well. With the Ring cyclotron, polarized protons and light ions are accelerated up to 100-400 MeV/u. Nucleon-nucleon interaction is weakest in this energy region and the reaction mechanism is expected to be simple, which enables us to investigate properties of nuclear interior. Furthermore, this energy region is optimum to study spin-isospin modes in nuclei.

Aiming at efficient deceleration and cooling of the energetic radioactive ions, development of an rf ion guide system which comprises a large He gas cell and an rf funnel structure in the cell is under progress. A proof of the principle (pop) machine has been successfully tested on-line for collection of 70-MeV/u Li-8 ions. A compact gas cell of 70 cm in length and 10 cm in diameter with a He gas pressure of 30 Torr was placed after a variable wedge shaped energy degrader. The ions stopped in the gas were extracted orthogonally to the beam axis by the dc field penetrated from the rf funnel structure. The ions follow the line of electric force toward the surface of the electrode, while they do not hit the electrode due to the presence of the rf barrier field. The ions move on the surface of the funnel structure toward the exit nozzle. The overall efficiency of the pop system was 10^-4, which can be separated into the gas stopping efficiency of 0.43% and the ion-guide efficiency of 2.4%. The former is limited by the volume of the cell and the pressure of the He gas. The latter is due to the present rf voltage limitation of 40 V. Both components could be increased up to 10% range by larger cell, higher pressure, and higher rf voltage, which would yield an expected overall efficiency of 1%.

High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Research Institute (JAERI) are jointly constructing an ISOL-based radioactive nuclear beam (RNB) facility at the Tandem accelerator of the Tokai Institute of JAERI by utilizing heavy-ion linacs and the related other equipment of the presently closed KEK-RNB facility as much as possible. The RNB energy available in the present project is continuous in the range of 0.1-8 MeV/u. Some details of the project are reported.

This paper introduces the CNS Radioactive-Ion Beam separator (CRIB), which can produce low-energy radioactive-ion beams by using the in-flight separation method. The technique of RI beam production and separation used for CRIB is discussed. We also report the first experiment at CRIB on the elastic resonance scattering of ¹²N+p and ¹¹C+p.

The AVF cyclotron at CYRIC has been replaced from K=50 MeV AVF cyclotron to K=130 MeV AVF cyclotron. All of the missions for replacement have been almost completed. It has started the commissioning for beam tuning and has partly been opened for experiments. Outline of the new plans by the new cyclotron will be presented including the RI beam projects under consideration.

A recoil mass separator designed to achieve a highest possible capability of the background rejection in the condition of inverse kinematics has been developed at Kyushu University tandem accelerator laboratory. Developments at accelerator have also been carried out to obtain a pulsed beam of high current and good emittance. With the mass separator and the pulsed heavy-ion beam, we have started the measurement of the ⁴He(¹²C,¹⁶O)γ reaction of astrophysical interest. Application of the mass separator to production of radioactive nuclear beams of high purity has also been planned.

We are planning to measure an analyzing power of elastic scatterings between polarized protons and skin nuclei ⁶He and ⁸He. From these experiments, one can derive information on the structure of the skin nuclei. For such experiments, a new Spin Polarized Solid Proton Target (SPSPT) system which can be operated at a high temperature and in a low magnetic field is under construction. As a target material, a naphthalene crystal doped with pentacene is used. Recently, a test experiments have been carried out, and a polarization of 18.4 ± 3.9% at a temperature of 100 K and in a magnetic field of 0.3 T have been obtained. The build up time of the proton polarization was 1.7 hours. The relaxation time was 21 ± 3 hours.

The new concept of γ-ray tracking will be the main characteristic feature of the next generation of powerful 4π γ-ray detection systems. The status of development of this mode of operation and preliminary results from the MARS prototype detector are presented. The European project AGATA, which will be the first full-scale implementation of the γ-ray tracking concept, is outlined.

CNS germanium detector array is introduced, which is dedicated for high-resolution γ ray spectroscopy of fast moving exotic nuclei produced in intermediate-energy direct reactions of unstable nuclear beam.

The last generation of γ-ray spectrometers has been designed to make high sensitivity measurements for nuclear structure studies. The experimental data obtained with the EUROBALL array have dramatically improved our understanding of nuclear structure at high spin and far from stability. A selection of recent experiments and of new results addressing the problem of superdeformation up to high excitation energy, of the proton-neutron paring and isospin mixing are here reviewed. In addition future perspectives concerning the use with radioactive beams are briefly discussed.

The success of high-resolution γ spectroscopy of hypemuclei has marked a great step in strangeness nuclear physics. By using a Ge detector array called Hyperball, precise level structure of several hypemuclei has been revealed, and the strengths of the spin-dependent ΛN interactions are experimentally determined from “hypernuclear fine structures”. In addition, the nuclear shrinking effect has also been confirmed from B(E2) measurements. The previous results are reviewed and a near-future plan of B(M1) measurement is described.

Experiments to study the decay of hot composite nuclei have been carried out with EUROGAM II γ-ray spectrometer, coupled to the DIAMANT charged-particle detector, at the VIVITRON accelerator at IReS in Strasbourg. Some relevant aspects related to the population of superdeformed bands have been addressed, on the basis of very exclusive data. We present the results for the composite nuclei ⁹⁰Ru and ¹⁶⁰Er produced in the reactions 120, 130 MeV ³²S + ⁵⁸Ni, and 191 MeV ³⁷Cl + ¹²³Sb, at excitation energies E_x≅ 55, 61 and 92 MeV, respectively Evidence is given of effects related to the angular momentum as well as to the location of the entry region.

Recently, various methods of γ-ray spectroscopy with radioactive-ion beams have been developed, which include intermediate-energy reactions of Coulomb excitation, inelastic proton scattering, one-neutron knockout, and projectile fragmentation. These methods have been used successfully to study low-lying structure of very neutron-rich nuclei lying far from the stability line. In this report, after briefly describing characteristic features of the experimental methods, recent studies of γ-ray spectroscopy on ¹²Be and ³⁴Mg are presented.

The GeV photon beam at SPring-8 is produced by backward-Compton scattering of laser photons from 8 GeV electrons. Polarization of the photon beam will be ∼100 % at the maximum energy with fully polarized laser photons. We report the status of the new facility and the prospect of hadron physics study with this high-quality beam. Preliminary results from the first physics run are presented.

The present status of the development of a Compton camera system for multitracer imaging is presented. The suitability of this system is confirmed by a test experiment using existing segmented planar germanium (Ge) detectors. A practical method is introduced in order to reconstruct a distribution image of spatially distributed γ-ray sources. It is shown that the depth position of γ-ray interaction in the Ge detector can be deduced by measuring the time difference between signals from cathode and anode.

No abstract received.

An overview of recent researches in Nuclear Physics undertaken in Italy under INFN organization will be presented. These researches span a very broad field: very low energies connected to astrophysical problems, the “classical” Nuclear Physics (structure of atomic nuclei and reaction dynamics), very high energies, in the so called ultra-relativistic regime, related to the inner structure of neutrons and protons as well as to Cosmo-genesis questions, applications to other disciplines.

A versatile radioactive multitracer technique has been developed at RIKEN Accelerator Research Facility about 11 years before. It enables efficient and simultaneous tracing of a number of elements under identical experimental conditions. Since 1991, the multitracer technique has been applied for an investigation of a behavior of various elements in chemistry, biochemistry, pharmaceutical sciences, medical sciences, nutritional sciences, agricultural sciences, and environmental sciences. Now, the multitracer has been used in more than 50 laboratories in the world. Its principle and features are presented with examples of recent application.

The following sections are included:

• Program

• List of Participants