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         List of seminars from April to September, 2000
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Date:     2000/10/11 (Wed.) 15:00-
Lecturer: Prof. Yu.A. Plis (Joint Institute for Nuclear Research, DUBNA)
Title: The new possibilities for polarized ion beam production
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
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Date:     2000/10/4 (Wed.) 15:00-
Lecturer: Shen WenQing (Shanghai Institute of Nuclear Research, 
          Chinese academy of Science)
Title: Program for RIB Physics and nuclear astrophysics in china and 
       Preliminary plan of Shanghai Laser Electron Gamma Source
Place:    RIKEN Main Bldg. 2F Seminar Room
                           The seminar will be given in English.
Abstract:
The brief introduction for Major State Basic Research Development Program 
in China and program for RIB Physics and Nuclear Astrophysics will be given. 
The preliminary plan of Shanghai Laser Electron Gamma Source on the planned 
Shanghai Synchrotron Radiation Facility will be described briefly also.
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Date:     2000/10/2 (Mon.) 15:00-
Lecturer: Pradip Kumar Sahu (Division of Physics, Hokkaido University)
Title: Nuclear equation of state and its aplication to heavy-ion collisions 
       and neutron star
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
The nuclear equation of state is still an unsettled issue 
though many experimental and theoretical efforts have been 
made in last decade. Experimentally, the baryon sideward 
flow and elliptic flow are the most promising observables. 
Recently the flow has been measured for heavy-ion collisions 
at AGS energies in $Au+Au$ systems, which provides further 
constraints on the hadronic models and the EOS employed.

We fix the explicit momentum dependent of the nucleon-meson
couplings within the relativistic model by the nucleon optical
potential up to 1 GeV of kinetic energy.
In this work, in a relativistic transport model, we performed
a systematic study of $Au + Au$ collisions in comparison to the 
recent experimental data on the collective flow of baryons at 
SIS to AGS energy regime.

In the second part, we calculate the nuclear equation of state 
by using the same dynamic momentum dependence constraints in 
the nuclear potentials and then employ to the neutron star 
structure calculations, where the composition of the particles 
are hyperons along with neutrons, protons and leptons.

Since the interaction between hyperon-nucleon and hyperon-
hyperon are not know very well, we vary the ratio of hyperon-
meson and nucleon-meson couplings from the analysis of
various experimental data on hypernuclei at KEK.

Finally, we discuss the appearance of hyperons with density,
the maximum mass of neutron star with recent observational 
value.
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Date:     2000/9/11 (Mon.) 15:00-
Lecturer: Shen WenQing (Shanghai Institute of Nuclear Research, 
          Chinese academy of Science)
Title: Research on isospin effect of projectile fragmentation reaction and 
       BUU calculation of total reaction cross section
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
The projectile fragmentation reaction in intermediate energy is one of 
the important reaction mechanizms for producing Radioactive Ion Beam. 
The research of isospin effect of projectile fragmentation reaction and its 
disappearance via experiment at Lanzhou and modified statistical abrasion 
ablation model will be described. The possible difference between experiments 
and calculation will be discussed. The total reaction cross section induced 
by radioactive beam was calculated via BUU equation with soft EOS and 
0.8 time Cugnon parametrizasion for nucleon-nucleon cross section in nuclear 
medium. Total reaction cross section in intermediate energy was calculated 
by HO-type density distribution, its parameter was obtained by fitting the 
total reaction cross section in relativistic energy. The comparisons with 
experiments and Glauber model calculation was described and discussed.
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Date:     2000/8/30 (Wed.) 15:00-
Lecturer: Eiji Ideguchi 
          (Department of Physics, Royal Institute of Technology, Sweden)
Title: "Enhanced" Superdeformation in 91Tc
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
Since the discovery of a superdeformed (SD) rotational band in 
83Sr, highly increased sensitivity obtained by combining the 
latest generation of gamma-ray spectrometers with charged particle 
detectors has allowed to identify new regions of superdeformation.
With the recent discovery of SD bands in 88Mo and 89Tc, the A~80 
mass region of SD nuclei is now extended to A~90. The SD states of 
these nuclei were reported to have large quadrupole deformations 
with deformation parameters beta_2 ~ 0.6. These findings were in 
agreement with Cranked Woods-Saxon Strutinsky calculations, which 
predicted Z=42 and Z=43 to be favored particle numbers at SD shapes 
in A~90 nuclei.
In the spectroscopic investigation of A~90 nuclei with the GAMMASPHERE 
spectrometer a new superdeformed rotational band has been observed in
91Tc. The average transition quadrupole moment measured for the band
indicates together with the large moment of inertia that this band 
has more elongated shape than in the neighboring A = 80-90
superdeformed nuclei. Theoretical interpretations of the band within 
the cranked Strutinsky approach based on two different Woods-Saxon 
potential parametrizations are presented. Even though an unambiguous 
configuration assignment proved difficult, both calculations indicate 
a larger deformation and at least three additional high-N intruder 
orbitals occupied compared to the lighter SD nuclei. 
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Date:     2000/8/28 (Mon.) 16:00-
Lecturer: Karsten Chmielewski 
          (Institut f\"ur Theoretische Physik, Universit\"at Hannover, Germany)
Title: Elastic and Inelastic Neutron-Deuteron Scattering with 
       $\Delta$-Isobar Excitation
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
  The three-nucleon system with explicit $\Delta$-isobar content is
  considered.  The inclusion of virtual $\Delta$-isobar excitation into
  the three-body scattering equations yields an effective three-nucleon
  force.  The influence of the $\Delta$-isobar on nd-scattering
  observables is studied.  We will also focus on the novel numerical
  techniques used for the solution of the three-body scattering
  equations for elastic and inelastic nd-scattering.
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Date:     2000/7/18 (Tue.) 15:00-
Lecturer: Yasuo Miake (Inst. of Physics, Univ. of Tsukuba)
Title: QGP formation and collective flow in high energy heavy ion collisions
       (高エネルギー重イオン衝突におけるＱＧＰ生成と集団運動)
Place:    RIKEN Main Bldg. 2F Seminar Room
                           The seminar will be given in Japanese.
Abstract:
ＣＥＲＮ・ＳＰＳにおける核子あたり１５８ＧｅＶの
鉛ビームによる高エネルギー重イオン衝突において、
クォークグルオンプラズマ（ＱＧＰ）の生成が確認されたとの報告が
本年２月に行われた。ＱＧＰ生成の根拠となった幾つかの
実験結果を紹介すると共に、高エネルギー重イオン衝突における
集団運動的振る舞いに核子あたり１０ＧｅＶ領域から１５０ＧｅＶ領域では
幾つかの興味ある変化が観測されている。１０ＧｅＶから１５０ＧｅＶの
エネルギー領域観測の重要性を述べたい。
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Date:     2000/7/13 (Thu.) 15:00-
Lecturer: Hitoshi NAKADA (Chiba University)
Title: Microscopic calculation of nuclear level densities applying the
shell model Monte Carlo method
Place:    RIKEN Main Bldg. 2F Seminar Room
                           The seminar will be given in English.
Abstract:
The auxiliary-fields Monte Carlo techniques in the nuclear shell
model (the shell model Monte Carlo) give us a method to compute
finite-temperature observables of nuclei from a microscopic standpoint. The
application to nuclear level densities, which was initiated by Y. Alhassid of
Yale university and the speaker, is one of the most successful ones. 
Present status of the SMMC
approaches to the nuclear level densities is reviewed. It is demonstrated
for the pf-shell nuclei that these approaches reproduce the densities up to
around the neutron resonance, which are important in astrophysics as well
as in reactors. Some new physics (e.g. parity-dependence) on the level
densities are also pointed out.
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Date:     2000/7/12 (Wed.) 15:00-
Lecturer: Gianluca Colo` (Dipartimento di Fisica, Universita` degli Studi, Italia)
Title: GIANT RESONANCES IN STABLE AND UNSTABLE NUCLEI
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
In recent times, a growing interest has been devoted to nuclei far from 
the stability line and the measurements of the strength function of a number 
of vibrational states has become possible. In this contest, it would be 
desirable to assess the reliability of the microscopic models which are 
based on Hartree-Fock plus RPA with effective interactions and which can 
take into account the damping mechanism of giant resonances. We present
novel results for the dipole response in the oxygen isotopes, by discussing
in particular the spreading of the response function due to the coupling with
two particle-two hole-type configurations. We compare with other (e.g., shell
model) calculations, as well as with recent experimental findings obtained
at GSI, Darmstadt.
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Date:     2000/7/7 (Fri.) 15:00-
Lecturer: Shalom SHLOMO (Cyclotron Institute, Texas A&M University, USA)
Title: Microscopic Calculation of Excitation of Isoscalar Giant Resonances
by Inelastic Alpha Scattering
Place:    RIKEN Exhibition Bldg.(TENJI-TOU) 1F AV Room
                           The seminar will be given in English.
Abstract:
We consider the problem of extracting the value of nuclear matter
incompressibility coefficient, K, from analysis of excitation cross section 
of the isoscalar giant monopole resonance (ISGMR) and the isoscalar
giant dipole resonance (ISGDR) by Alpha scattering. We will discuss
in particular; (i) the accuracy of the strength function S(E)
obtained from current Hartree-Fock (HF) random-phase-approximation (RPA),
(ii) the effect of dissipation on the centroid energies of the ISGMR and
the ISGDR and (iii) the accuracy in extracting S(E) from the experimental
cross section by using the collective transition density instead of
the microscopic transition density determined in HF-RPA calculation.
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Date:     2000/6/23 (Fri.) 16:00-
Lecturer: N. Kalantar-Nayestanaki (KVI, The Netherlands)
Title: Probing few-body systems with Bremsstrahlung
Place:    RIKEN Main Bldg. 1F Seminar Room
                ^^^^^^^^^^^^^^^^^^^^^^^^^^
                           The seminar will be given in English.
Abstract:
A series of bremsstrahlung measurements have been
performed at KVI with the new superconducting cyclotron, AGOR, aiming to
investigate the behavior of the nucleon-nucleon interaction beyond
what is already known from the elastic $N\!N$ interaction and the properties
of the deuteron. Nucleon-nucleon bremsstrahlung is the simplest process
used for such studies as it involves the strong interaction between two
nucleons and the well-known electromagneticinteraction. At KVI, we have
used the high-quality polarized beam of 190 MeV protons to perform the most
complete experiment to date on proton-proton and proton-deuteron systems.
The second system was chosen so that one is able to study all possible
bremsstrahlung channels, including the neutron-proton system.
High precision cross-section and analyzing-power data have been obtained
for the real-photon production on these systems enabling one to extract
information on the properties of the interacting nucleon as it propagates
in an intermediate state, the role of virtual nucleon-resonance excitation
at lower energies and the role of two-body effects such as MEC. Simultaneously,
we have measured the lepton pair production on both systems. This latter
process, despite its lowercross section, avails us with extra degrees of
freedom, namely the non-zero invariant mass and the outgoing lepton angles
making the study of other structure functions than the transverse one possible.
Experimental results of the real and virtual photon production on both
systems, along with the results of theoretical calculations will be discussed.
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Date:     2000/6/20 (Tue.) 16:00-
Lecturer: Alberto Mengoni (ENEA-Bologna and INFN-Bologna)
Title: Nuclear Physics and Astrophysics at CERN-n_TOF
Place:    RIKEN Main Bldg. 3F Seminar Room
                           The seminar will be given in English.
Abstract:
A neutron time-of-flight facility, n_TOF, is under construction 
at CERN. The neutron beam will be produced by spallation
induced by the 24 GeV proton beam of the PS accelerator
impinging on a Lead target. n_TOF will produce an unprecedent 
neutron flux in the energy range from 1 eV to 250 MeV with 
very high resolution after a flight path of 200m.
The physics potential of n_TOF has been identified in three
main components: 
1) measurements of neutron cross sections relevant for Nuclear
Astrophysics
2) measurements of neutron cross sections relevant for Nuclear Waste
Transmutation     and related Nuclear Technologies
3) neutrons as probes for basic Nuclear Physics.
In this Seminar I will give a description of the Nuclear 
Physics program of n_TOF and discuss some of the
proposed experiments to be performed in the first three
years of operation.
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Date:     2000/6/19 (Mon.)
(1) 14:00-
Lecturer: Thomas Aumann (GSI)
Title: Electromagnetic excitation of relativistic secondary beams
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
In this presentation we report on new experimental results on the dipole
response of light neutron-rich nuclei in the  mass region around $A=20$.
The E1 strength function is deduced from a measurement of the
differential electromagnetic excitation cross section $d\sigma/dE^*$ 
at high bombarding energies ($E\approx 600$~MeV/u).  The secondary beams
of unstable nuclei were produced at GSI by fragmentation of $^{40}$Ar
primary beam and selected with the Fragment Separator FRS. The inelastic
scattering on a secondary Pb target and subsequent neutron decay is
investigated in a kinematically complete measurement by the use of the
LAND setup, which allows for a reconstruction of the excitation energy.
The oxygen isotope chain is studied systematically, ranging from the
stable isotope $^{17}$O up to $^{22}$O. For the neutron-rich isotopes,
we observe a considerable amount of the dipole strength at low excitation
energies, below the giant dipole resonance region, reaching up to about
10% of the energy weighted sumrule (integrated up to 15 MeV excitation
energy). The differential cross sections are compared to shell model
calculations and RPA type of calculations using different effective
interactions. Results for other neutron-rich nuclei, like e.g. $^{11}$Be
and $^{15-17}$C, which were contained in the mixed secondary beam of the
same experiment, will be discussed as well. From the low-lying dipole
strength observed for these weekly bound systems, information on the
single particle structure, like angular momentum of the valence neutron
and spectroscopic factors, can be deduced. We compare our experimental
findings to the results obtained with other experimental techniques and
with shell model calculations.

(2) 15:00- (or after the first seminar)
Lecturer: Peter von Neumann-Cosel
          (Institut fuer Kernphysik, TU Darmstadt, Germany)
Title: Electron scattering and elementary excitation modes of nuclei
Date:     2000/6/19 (Mon.) 15:00-
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
High-resolution inelastic electron scattering provides a unique
tool for the study of elementary electric and magnetic excitation modes
in nuclei.  Some examples of recent progess in the field are presented.
Coincidence experiments explore the complex electric giant resonance
strength distributions and their decay properties. Magnetic dipole and
quadrupole modes are investigated by 180 degree scattering with emphasis
on the interplay of spin and orbital motion and possibles signature of
non-nuclear degrees of freedom.
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Date:     2000/6/16 (Fri.) 16:00-
Lecturer: Hiroaki Utsunomiya (Konan University)
Title: Photodisintegration of $^{9}$Be for nuclear astrophysics
Place:    RIKEN Main Bldg. 3F Seminar Room
                           The seminar will be given in English.
Abstract:
Photoneutron cross sections were measured for $^{9}$Be
from threshold to 6 MeV with a laser-electron MeV photon source at ETL.
B(E1), $\Gamma$, and E$_{R}$ were deduced for the 1/2$^{+}$ and the
5/2$^{+}$ states by the least-squares fit to the data.
$\Gamma_{\gamma}$ was deduced from the energy-integrated cross section
for the 5/2$^{-}$ state.  Astrophysical implications of the data in
conjunction with the r-process in the neutrino-driven wind of
core-collapse supernovae are discussed.   I would also like to discuss
nuclear physics with help of theorists at RIKEN.  Finally, I would be
happy if I could discuss the feasibility of this type of experiments
with radioactive nuclei at RIKEN.
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Date:     2000/6/8 (Thu.) 14:00-
Lecturer: Michael Thoennessen (MSU)
Title:    Structure of the particle-unbound nuclei 7,9He and 10Li
Place:    RIKEN Main Bldg. 3F Seminar Room
                           ^^^^^^^^^^^^^^^
                           The seminar will be given in English.
Abstract:
Neutrons from the breakup of 30 MeV/u  12Be on a 200 mg/cm^2 9Be target
were detected in NSCL's Neutron Wall in coincidence with the fragments
6,8He and 9Li. The distributions of the relative fragment-neutron
velocities show characteristic final-state interactions as well as
a dependence on the initial state. The results for 9He are similar
to those for 10Li and indicate the presence of a low-lying s-state
characterized by a scattering length of order -10 fm. The new state must
be at or below an effective energy of 0.2 MeV, well below the presumed
p-state which implies that 9He also has an s-intruder state as the
ground state.
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        Contact person of Nuclear Physics Seminar
        T. Nakatsukasa and T. Yamaguchi (RI Beam Science Lab.)
        (email) seminar@rarfaxp.riken.go.jp
        (FAX)   048-462-4689
        (WEB)   http://rarfaxp.riken.go.jp/~seminar/

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Date:     2000/6/7 (Wed.) 15:00-
Lecturer: C.Samanta (Saha Institute of Nuclear Physics, India)
Title:    Proton elastic scattering from 4,6,8He and 6,7,9,11Li
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
While $^{11}$Li is known to be a halo nucleus  with two neutrons around
a $^9$Li core, the neutrons in $^6$He are predicted to form a skin
around its $^4$He core. Both nuclei have very low breakup thresholds.
To understand the structure and reaction dynamics of these nuclei, a
consistent analysis of the available low energy (25A - 75A MeV) proton
elastic scattering data on $^{4,6,8}$He and $^{6,7,9,11}$Li nuclei
is carried out in a folding model framework. A finite-range, momentum,
density and isospin dependent NN interaction (SBM) is folded with realistic
densities of different nuclei. To fit the elastic angular distribution, the
real part of the folded potentials are multiplied by a renormalization factor
(N$_R$). Except for the p + $^4$He scattering at low incident energy, the
N$_R$ values are found to be significantly different from 1.0, indicating
appreciable channel coupling effects in the energy region considered.
Variation of N$_R$ values with incident energies for $^6$He and $^{11}$Li
is much smaller compared to $^8$He and $^6$Li.  Implications of these
results will be discussed.
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Date:     2000/5/15 (Mon.) 16:00-
Lecturer: Takumi Muto (Dept. of Phys., Chiba Institute of Technology)
Title:    Nuclear Experiment on the Giant Gamow-Teller State and
          Pion Condensation
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract: Possible existence of pion condensation depends sensitively on
the strength of short-range correlations between baryons, which are
simulated by the Landau-Migdal parameters g'.  Recent experimental data
on the giant Gamow-Teller (GT) state provided renewed information on g',
especially the difference between $g'_NN$ and $g'_{N\Delta}$. We review
the analysis for deducing $g'_NN$ and $g'_{N\Delta}$ from the GT experiment,
and discuss critical density and equation of state for pion condensation
which may realize in highly dense matter.
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Date:     2000/5/11 (Thu.) 14:00-
Lecturer: Kazunori Kohri (YITP, Kyoto Univ.)
Title:    Standard Theory of Big-Bang Nucleosynthesis and 
          Present Observation of Light Elements
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in Japanese.
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Date:     2000/5/10 (Wed.) 14:00-
Lecturer: Serdar Kuyucak (Australian National University)
Title:    Description of quadrupole-octupole collectivity in boson models
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
Advances in detector technology in recent years have enabled detailed
studies of negative parity spectra in a range of actinide nuclei, where the
octupole correlations are expected to play a significant role.
These new data provide fresh challenges for collective models, the most
interesting one being the description of the conjectured transition from
the octupole-vibrational to the octupole-deformed shapes in actinides.
Simultaneous description of quadrupole-octupole collectivity in nuclei
presents a formidable challenge for nuclear models due to both the
increased number of parameters and the much larger model spaces.  Numerical
diagonalization, though possible in supercomputers, is unlikely to be very
fruitful without a guiding hand.  Therefore, investigation of a model's
capabilities using mean field theory, which provides simple estimates for
main spectroscopic observables (e.g., band excitation energies and
electromagnetic transitions), would be essential before making more serious
attempts with exact solutions.
In this talk a mean field study of the quadrupole-octupole degree of
freedom in collective nuclei within the framework of the spdf-boson model
is presented.  For realistic choices of the Hamiltonian parameters, the
ground state of the system is shown to remain axially symmetric, which
considerably simplifies the mean field treatment.  Study of shape-phase
transitions in the spdf-IBM shows that the critical point for the onset of
octupole deformation occurs at zero interaction strength after parity
projection.  This is in complete contrast to the quadrupole case where
a finite interaction strength is necessary for the onset of deformation.
A systematic survey of excitation energies and electric transitions for
one-phonon states is given, which will provide a useful guidance for
detailed studies of negative parity states within the spdf-boson model.
In addition, a complete description of positive and negative parity bands
can be obtained from the mean field results via parity and angular momentum
projection.
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Date:     2000/4/28 (Fri.) 16:00- 
Lecturer: Yoshinori Akaishi
          (Institute of Particle and Nuclear Studies, KEK)
Title:    Coherent lambda-sigma coupling in light hypernuclei
Place:    RIKEN Main Bldg. 1F Seminar Room
                           The seminar will be given in English.
Abstract:
It is found that the suppression due to two-body $\Lambda N$-$\Sigma N$
coupling solves the overbinding problem in $^{5}_{\Lambda}$He but it, in 
turn, causes a severe underbinding in the four-body systems. The shortage
of this binding is overcome by introducing the $\Lambda$-$\Sigma$ coupling
explicitly which is equivalent to the $\Lambda NN$ three-body force. This
three-body force becomes strong in the $0^{+}$ states of $^{4}_{\Lambda}$H
and $^{4}_{\Lambda}$He according to the coherently added enhancement. The
$0^{+}$-$1^{+}$ splitting in $^{4}_{\Lambda}$H and $^{4}_{\Lambda}$He is
found partly due to the $\Lambda N$ spin-spin interaction and partly due
to the $\Lambda$-$\Sigma$ coupling in the recent Nijmegen soft-core
potential. This coherent $\Lambda$-$\Sigma$ coupling becomes much more
important in neutron-excess and neutron-rich hypernuclei.
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Date:     2000/4/12 (Wed.) 17:00-
Lecturer: Francesco Iachello (Yale University)
Title:    The discovery of supersymmetry in nuclei
Place:    RIKEN Nishina Hall
                           The seminar will be given in English.
Abstract:
In August 1999, Metz et al reported direct experimental evidence for the
occurence of supersymmetry in nuclei.  In this colloquium, supersymmetry and
its role in nuclear physics will be reviewed.  Evidence for its occurence
will be presented.  Implications to other fields (particle physics, condensed
matter physics and molecular physics) will be briefly discussed.
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