| Lastname, Firstname |
Title |
| Abstract |
| |
| Aliotta, Marialuisa |
Radioactive beams for astrophyics:
recent studies and open questions |
| The talk will present an overview of some recent
experimental studies relative to explosive nuclear burning in
astrophysical scenarios such as novae and X-ray bursts.
Current status and open questions will also be discussed. |
|
Badarch, Urnaa
|
Density dependence of the symmetry
energy. |
| One of the major puzzles of modern nuclear
many-body theory is the density dependence of the symmetry energy. The
variation of the symmetry energy with total density is of high
importance for a large variety of phenomena ranging from fragmentation
in high energy
heavy ion reactions to the structure of neutron stars. Despite many
experimental and theoretical attempts there are remaining uncertainties
leaving open questions. We use DDRH field theory to investigate the
symmetry energy, the compressibility, and other
thermodynamical quantities of nuclear matter over a large density range
on a fully microscopic level. Since we use interaction from
Dirac-Brueckner theory our approach is well defined in a
diagrammatically sense. The special role of the delta-($a_0(980)$)
meson for the effective masses is discussed. The DDRH approach allows a
fully self-consistent derivation of the equation of state and the
symmetry energy at any proton-to-neutron fraction. A comparison of the
DDRH results to those from phenomenological approaches shows
significant deviations at very low and high densities relevant for
neutron star calculations. The effects on neutron star matter in
beta-equilibrium are discussed. Results for the mass-radius relation,
i.e. the equation of state of neutron stars are discussed. |
| |
| Barbieri, Carlo |
Applications of Green's function
techniques to nuclear structure (and atoms) |
| The talk will cover recent ab-initio calculations
of the Faddeev expansion method to both nuclei and light atoms. For
atoms, the Faddeev-RPA approximation has been found to match the best
calculations of ionization energies and strengths (corresponding to
separation energies and spectroscopic factors in nuclear physics).
First calculations for nuclei will be reported. The relevance of this
method to the the study of transfer reactions and nuclear response will
be discussed. |
| |
| Blank, Bertram |
Tow-proton radioactivity studies |
| I will present an overview of present and past
two-proton radioactivity studies. Experimental results will be compared
to theoretical predictions and new experimental developments will be
described. |
| |
| Boretzky, Konstanze |
Pygmy Dipole Strength in Exotic
Nuclei and the Neutron Equation of
State |
| The properties of exotic nuclei are ideally
studied in
inverse-kinematics experiments at high beam energies using the
FRS-LAND facilities at GSI, allowing exclusive measurements of
all projectile-like particles following the excitation of the
projectile in a high-Z target (Pb). At beam energies of ~500 MeV/u
electromagnetic excitations are dominated by dipole transitions. In an
experiment utilizing secondary beams of neutron-rich Sn
isotopes $^{129-132}$Sn and neighbouring nuclei with similar A/Z
ratio a substantial fraction of dipole strength at energies below
the giant dipole resonance (GDR) is observed. For $^{130}$Sn and
$^{132}$Sn this strength is located in a peak-like structure
around 10 MeV and exhibits a few percent of the Thomas-Reiche Kuhn
(TRK) sum-rule strength. Several calculations predict the
appearance of dipole strength at low excitation energies in
neutron-rich nuclei, often referred to as pygmy dipole resonance
(PDR). In a macroscopic picture, the PDR is discussed in terms of
a collective oscillation of excess neutrons out of phase with the
core nucleons. Recent random-phase-approximation calculations
show a strong correlation of the PDR strength to the density
dependence of the symmetry energy and thus a link to the neutron
skin size. Consequences from the experimental findings in
$^{130}$Sn, $^{132}$Sn and $^{208}$Pb for the neutron-skin sizes,
the symmetry energy and the neutron equation of state (EoS) will
be discussed. |
|
| Brown, Alex |
Hybrid
Methods for Nuclear Structure |
| I will review some recent results for
shell-model configuration mixing and Skyrme Hartree-Fock calculations
for nuclei in the region A=20-60, and review the strong and weak
aspects of each method. Hybrid methods involve making use of the best
aspects of both methods, together with input from renormalized NN
interactions. |
|
| Brunner, Thomas |
Measurements of Electron Capture
Branching Ratios at the TITAN Ion Trap Facility to Evaluate Double-Beta
Decay Nuclear Matrix Elements |
| The TITAN (TRIUMF's Ion Traps for Atomic and
Nuclear physics) trap system is a new facility whose primary
application is high-precision atomic mass measurements on short-lived
radio-nuclides. Mass measurements are performed with a Penning-trap
mass spectrometer in combination with an EBIT (Electron Beam Ion Trap),
which is used as a charge breeder to enhance the precision of mass
measurements.
The EBIT offers the possibility to measure nuclear-decay electron
capture branching ratios (ECBRs) on stored radio-active ions through
X-ray spectroscopy. With no electron beam, the EBIT traps ions with
electrostatic potentials applied to drift tubes and a strong magnetic
field provided by two coils in the Helmholtz configuration giving a
visible access to the trap center. In comparison to conventional
techniques, the advantage of an ion trap is the backing free storage of
ions and thus a lower background. The EBIT, combined with the wide
range of radioactive isotopes supplied by TRIUMF's ISAC facility,
offers a novel approach to measure ECBRs for odd-odd intermediate
nuclei involved in double-beta decay ($\beta^-\beta^-$).
In the neutrinoless $\beta\beta$ decay, the neutrino mass is a function
of the nuclear matrix elements and the transition probability. If
$0\nu\beta\beta$ decay is observed in experiments such as NEMO,
Majorana and EXO, ECBRs can be used to obtain a detailed knowledge on
the transition nuclear matrix elements from which the neutrino mass can
then be evaluated. |
| |
| Enders, Joachim |
Polarized Electrons at Low
Momentum Transfers - Technical Developments and Planned Experiments at
the S-DALINAC |
| For future use at the superconducting Darmstadt
electron linear accelerator S-DALINAC, a source of polarized electrons
is being developed and tested, first as an offline test stand.
Longitudinally polarized photo-electrons are produced using a pulsed
diode laser and GaAs photo-cathodes and are preaccelerated
electrostatically to 100 keV. First measurements of beam parameters as
well as the status of technical developments will be discussed.
Furthermore, planned experiments with polarized electron and photon
beams at low energies and momentum transfers will be presented. First
tests (with unpolarized beams) searching for parity-violation effects
in photo-induced fission have already been performed. Electron
scattering experiments on light nuclei are foreseen to elucidate the
role of, e.g., mesonic exchange currents and of the three-body force in
few-body systems. |
| |
| Gade, Alexandra |
Nuclear spectroscopy with fast
exotic beams |
| |
| |
| Geissel, Hans |
Experiments with stored exotic
nuclei with FRS-ESR |
| |
| |
| Herfurth, Frank |
Ion traps and nuclear spectroscopy |
| Ion trap setups like SHIPTRAP, ISOLTRAP or the
planned MATS facility provide clean and well-controlled samples of
short-lived nuclei. This is an ideal prerequisite for nuclear decay
spectroscopy either using the backing free, well localized sample in
the trap or the high mass resolving power and long storage times of a
Penning trap for spectroscopy after the trap. Demonstration experiments
have been performed on a number of trap setups and will be presented.
In addition, this presentation focuses on future experiments for
instance at the MATS setup at FAIR or TRIGA-Trap at the research
reactor in Mainz. Detailed alpha spectroscopy will be used to measure
the lifetime of excited nuclear states for the determination of, for
instance, quadrupole moments of 2+ states. The electrons shaken off
from the recoil will be extracted out of the magnetic field and deliver
the position information from the alpha decay and the subsequent
electron conversion decay and hence the lifetime of the state populated
by the first decay. |
| |
| Herlert, Alexander |
The HIE-ISOLDE Project |
| Forty years after ISOLDE started operation at
CERN in 1967 it is still today the leading ISOL facility in terms of
the variety of extracted radioactive beams. An increasingly important
component during the last years has been the REX-ISOLDE
post-accelerator that presently can accelerate most ion beams produced
at ISOLDE up to a maximum energy of 3 MeV/u. The HIE-ISOLDE project
includes several important upgrades of the present facility. The
existing post-accelerator will be extended with an intermediate step
with acceleration to 5.5 MeV/u and the final objective being to provide
radioactive beams up to 10 MeV/u. For the extension superconducting
technology will be used. The beam quality will be improved in several
respects: through the installation of an RFQ cooler, a new resonant
laser ionization system, and a renovated High Resolution Mass
Separator. Combined with the continuing target and ion source
developments this will provide significant improvements for experiments
and give a total of more than 1000 different ISOL beams. Finally, the
driver beam intensity will be increased, at first due to a faster
cycling of the PS Booster accelerator, at a later stage due to the new
injector accelerator Linac-4. The target design will be adapted to
accommodate this higher intensity. The presentation will focus on the
technical improvements and will give selected examples of the physics
possibilities that will emerge as the different parts of the project
are implemented. |
| |
| Higa, Renato |
alpha-alpha scattering within Halo
EFT |
| Recently, rare exotic nuclei have drawn a lot of
interest due to properties that challenge traditional knowledge gained
from studies of stable nuclei. Particularly interesting is the
formation of clusters and halo structures, whose small bindings lead to
threshold phenomena with important consequences for nuclear
astrophysics. In many cases the binding among clusters is much smaller
than the exitation energy of each separate cluster, making them
suitable systems for employing Effective Field Theory (EFT) techniques.
Halo EFT has been developed and successfully applied to neutron-alpha
scattering, with a proper account of the $P_{3/2}$ resonance around 1
MeV. However, in many systems Coulomb interactions play a significant
role, therefore an extension which incorporates these effects is highly
desirable. I will present such an extension, based on previous works by
Kong and Ravndal, with application to low-energy alpha-alpha scattering. |
| |
| Holt, Jason |
Low Momentum Interactions for
Nuclear Structure |
| This talk will focus on presenting recent results
and future prospects of a theoretical program which aims to use
low-momentum interactions to describe nuclear structure properties of
medium-mass nuclei. Using two-nucleon (NN) low-momentum interactions
$V_{{\rm low}\,k}$, we study collective isovector valence shell
excitations (mixed-symmetry states) of nuclei in the mass A=90 region.
I will discuss the insights we gain into the underlying mechanisms
driving the formation and evolution of these structures in the N=52
isotones and emphasize the close connection this work has with recent
experimental investigations such as g factor measurements and electron-
and proton-scattering cross sections. Variations in the
NN-interaction-only results with the resolution/cutoff scale suggest
the need for many-body forces, and I will discuss the first steps taken
to incorporate three-nucleon interactions in this program. |
| |
| Karasu Uysal, Ayben |
Isovector Dipole Excitations in
Hot Nuclear Matter |
| We study the isovector dipole excitations in
nuclear matter by
employing the linearized Landau-Vlasov equation at finite
temperature using Skyrme and Gogny forces for infinite nuclear
matter and Skyrme force, Gogny force and Landau-Migdal interaction
for finite nuclei in semiclassical Thomas-Fermi approximation. We
calculate the giant dipole resonance (GDR) strength function for
these cases for 120Sn and 208Pb and compare our results. |
| |
| Kowalska, Magdalena |
Structure of light nuclei derived
from their ground-state properties: masses, spins, moments, radii. |
| Light nuclei host a variety of intriguing nuclear
phenomena: They form halos, clusters, or molecular structures, where
the latter very often correspond to strongly deformed shapes; the
effect of a magic numbers seems to erode to the point of disappearance,
as is the case for the 'island of inversion' around N=20. Several
modern theoretical approaches successfully describe these properties:
cluster models, ab initio calculations (available up to A=10), or new
shell model approaches, such as the Monte Carlo or no-core shell model.
In order to test and refine these theoretical descriptions of the
few-nucleon systems, the corresponding experimental observables have to
be available, and the nuclear ground-state properties: masses, spins,
magnetic and electric moments, and charge radii, represent such
model-free observables. In this talk I will present recent obtained
with two experiments located at ISOLDE/CERN: high-precision Penning
trap mass spectrometer ISOLTRAP and collinear laser-spectroscopy and
beta-NMR setup COLLAPS. These results include mass, magnetic moment,
and charge radius of the proton halo candidate $^{17}$Ne, which
characterize the main components of its ground-state configuration. The
magnetic and quadrupole moments of $^{9,11}$Li, which determine to
which extend $^9$Li core stays inert in $^{11}$Li will be also
discussed. Finally, I will present spins and magnetic moments of
$^{29,31,33}$Mg, which help to determine the physics mechanism driving
the 'island'. |
| |
| Krücken, Reiner |
Probing Shell closures and shape
coexistence with MINIBALL |
| In this contribution selected recent results on
spectroscopic investigations with the MINIBALL Gamma-ray spectromter
will be presented. On one hand results from Coulomb-excitation and
first transfer experiments at REX-ISOLDE will discussed, which concern
the investigation of shell evolution and shape coexistence. Particular
examples concern results at the boarder of the island of inversion,
near the doubly magic nuclei $^{78}$Ni, $^{132}$Sn, as well as first
Coulex experiments in the A=200 mass region. In addition results from a
knock-out experiment at the GSI Fragment Speparator with MINIBALL will
be presented. The results allow for the first time a clear
determination of the ground state spin in $^{55}$Ti as well as
occupation probabilities of the relevant single-particle states. The
results will be compared to modern shell model calcultations. |
| |
| Lenske, Horst |
Relativistic Density Functional
Theory |
| The DDRH theory as a fully covariant and
thermodynamically consistent density functional field theory is used to
investigate the dynamical structure of in-medium NN interactions.
In-medium NN interactions are obtained from Dirac-Brueckner
calculations. The interaction vertices are treated on the level of the
Lagrangian as Lorentz-scalar functionals of the field operators.
Results for the equation of state of infinite nuclear matter,
hypermatter, and neutron starts are discussed. Binding energies of
finite nuclei are well reproduced on a level of accuracy of a few
percent. In order to achieve a better understanding of density
dependent effects, we investigate their contribution to dynamical
scenarios involving excitations at non-vanishing energy and momentum
transfer. We choose Landau's Fermi-liquid theory and extend the
approach to relativistic density functionals. In order to retain the
field theoretical structure we derive the interaction functional in a
general from by second variation with respect to the field operators.
The Landau-Migdal-Parameters are obtained by expanding the interaction
amplitudes around the ground state expectation value. We analyze the
impact of rearrangement effects in the quasiparticle interaction, which
always occur in a density dependent formalism. An important feature is
the remarkable modification of the variationally derived Landau-Migdal
interaction in asymmetric matter by isovector effects due to the
neutron excess. |
| |
| Maris, Pieter |
Recent advances in ab initio
calculations of nuclear structure |
| I discuss recent developments in "ab initio"
calculations of nuclear
structure using basis function expansion methods. In principle any
nuclear potential can be used as input for such calculations, though
numerical convergence depends on the softness of the potential.
Renormalizations methods such as Lee-Suzuki and similarity group
transformations have been used to improve convergence. Our
calculations with chiral effective two-nucleon and three-nucleon
potentials and with a phenomenological two-body potential (JISP16)
give a good description of a range of properties of light nuclei. |
| |
| Neff, Thomas |
Structure and reactions of light
nuclei in the Fermionic
Molecular Dynamics approach |
| Light nuclei show a wealth of exotic phenomena
like clustering and halos. We aim at a consistent description of light
nuclei in the Fermionic Molecular Dynamics (FMD) approach, a
microscopic many-body
model that uses Slater determinants built with Gaussian wave packets
as basis states. We employ an effective interaction derived from the
realistic Argonne V18 interaction by explicitly implementing shortrange
central and tensor correlations using the Unitary Correlation Operator
Method.
We will show results for nuclei in the p- and sd-shell, looking at
binding energies, spectra, charge and matter radii, electromagnetic and
weak transitions. The FMD wave functions can be analyzed with respect
to clustering and shell model occupations. The structure of 12C will be
analyzed in detail with a special emphasis on the Hoyle and other
cluster states. The implementation of resonance and scattering boundary
conditions also allow us to study low-energy nuclear reactions like the
radiative capture reaction 3He(alpha,gamma
)7Be. |
| |
| Nogga, Andreas |
Using light nuclei to probe chiral
nuclear interactions |
| Chiral perturbation theory is a promising
approach to systematically develop nuclear interactions. For this
endeavor the light nuclei are especially interesting laboratories since
they are specifically sensitive to subleading parts of the
interactions, e.g. three-nucleon interactions. In this talk, I will
review recent results for nuclear bound states based on chiral
interactions and discuss their implications for further developments of
chiral interactions. |
| |
Nowacki,
Frederic
|
Shell
evolution far from stability in the (sd-pf) region
|
|
|
| Orrigo, Sonja |
Correlation effects and continuum
spectroscopy in light exotic nuclei |
| The spectroscopy of exotic nuclei is one main
topic of modern nuclear structure physics. Unexpected phenomena have
been observed in light n-rich nuclei. The enhanced correlation dynamics
makes possible new continuum excitation modes, the Fano Resonances, a
class of states above the neutron emission threshold due to dynamical
core polarization effects, characterized by asymmetric line shape. By
the Quasiparticle-Core Coupling model we show that the coupling of 1QP
and 3QP core-excited components leads to sharp resonances in the
low-energy continuum of the n+core system, with interference effects.
Theoretical calculations are presented for $^{15}$C, $^{17}$C and
$^{19}$C, giving information on the evolution of the phenomenon with
the neutron excess. The comparison with the $^{15}$C experimental data
shows a very good qualitative agreement.
Differently from well bound stable nuclei, in weakly bound n-rich
nuclei the relevant energy scale is given by the separation energy of
valence particles (few hundreds of keV). Thus interactions down this
order of magnitude have to be included, such as pairing effects, which
are complementary by creating a genuine type of configuration mixing
already at the mean-field level. Single-nucleon transfer reactions are
investigated as tool for continuum spectroscopy in nuclei such as
$^{10}$Li. We present a DWBA approach which allows to treat the case of
unbound final states, applied to the $^{9}$Li(d,p) $^{10}$Li reaction
at 3 and 20 MeV/u. |
| |
| Paar, Nils |
Inclusive neutrino-nucleus cross
sections based on the
relativistic mean-field theory |
| Inclusive neutrino-nucleus cross sections are
studied within consistent relativistic mean-field theoretical
framework. The weak
lepton-hadron interaction is expressed in the standard current-current
form, the nuclear ground state is described with the
relativistic Hartree-Bogoliubov model, and the relevant transitions to
excited nuclear states are calculated in the relativistic quasiparticle
random phase approximation. Illustrative test calculations are
performed for charged-current neutrino reactions on $^{12}$C, $^{16}$O,
$^{56}$Fe, and $^{208}$Pb, and results compared with previous studies
and available data. Using the experimental neutrino fluxes, the
averaged cross sections are evaluated for nuclei of interest for
neutrino detectors. We analyze the total neutrino-nucleus cross
sections, and the evolution of the contribution of the different
multipole excitations as a function of neutrino energy. It is shown
that the knowledge on spin-dipole and excitations of higher
multipolarities is of outmost importance for reliable microscopic
description of neutrino-nucleus reactions. The cross sections for
reactions of supernova neutrinos on $^{16}$O and $^{208}$Pb target
nuclei are analyzed as functions of the temperature and chemical
potential. |
| |
| Pakarinen, Janne |
Competing structures in light Pb
nuclei; extending in-beam gamma-ray measurements to odd-mass Pb isotopes |
| In very neutron deficient Pb isotopes, both
experimental and theoretical evidence for shape coexisting
configurations has been achieved [1,2]. This phenomenon becomes
transparent particularly at the neutron midshell, where the competing
structures intrude down to energies close to the spherical ground
state. Together with the spherical ground state, they form a unique
triplet of 0$^{+}$ states in $^{186}$Pb, each of which can be
associated with a different shape [3]. However, no unambiguous evidence
regarding their shape has been achieved in in-beam experiments. To
probe this, one could, for example, study rotational coupling in the
odd-mass Pb isotopes. In a recent in-beam recoil-decay tagging
experiment at JYFL, we have observed excited states in $^{185}$Pb for
the first time. In this experiment we collected gamma-gamma-coincidence
data that enabled us to construct a level scheme on top of the
13/2$^{+}$ alpha decaying isomeric state in $^{185}Pb. It reveals a
band structure which clearly represents strong coupling of an odd
i$_{13/2}$ neutron to a prolate core. The interpretation of these new
findings will be discussed with respect to the shape coexistence
phenomena in light Pb isotopes.
[1] J.L. Wood et al., Phys. Rep. 215, 101 (1992).
[2] R. Julin, K. Helariutta and M. Muikku, J. Phys. G: Nucl. Part.
Phys. 27, R109 (2001).
[3] A.N. Andreyev et al., Nature, 405, 430 (2000). |
| |
| Papakonstantinou, Panagiota |
Giant Resonances with Correlated
Realistic Interactions and Second RPA |
| Second RPA (SRPA) has been applied to study giant
resonances (GRs) of closed-shell nuclei. A correlated realistic
interaction, constructed within the Unitary Correlation Operator Method
(UCOM) so as to take into account short-range correlations, is used to
describe the Hartree-Fock (HF) ground state and the residual couplings.
It is found, that the second order configurations included in SRPA
produce sizable effects, compared to first-order RPA, by effectively
dressing the underlying HF single-particle states with self-energy
insertions. The effect appears essential for a realistic description of
the isovector dipole and isoscalar quadrupole GRs, when using
UCOM-correlated interactions. Self-consistency issues of SRPA and the
role of missing three-body effects are discussed. |
| |
| Papenbrock, Thomas F. |
Coupled-cluster theory for nuclei |
| I will give an overview of ab-initio nuclear
structure calculations based on coupled-cluster theory. The focus will
be on recent results obtained for weakly bound and unbound Helium
isotopes, the treatment of three-nucleon forces, and the extension to
medium-mass nuclei. |
| |
| Quaglioni, Sofia |
Ab initio nuclear reactions within
the NCSM/RGM approach |
| We report on recent results of our work in the
direction of
building an {\em ab initio} method for low-energy light-ion
reactions by augmenting the no-core shell model (NCSM)$^{1,2}$ to
include clustering and resonant and non-resonant continuum. For
this purpose, we adapt the resonating group method$^{3}$, a
microscopic technique in which the many-body problem is mapped
onto various channels of nucleon clusters and their relative
motion. In our approach we use NCSM wave functions for the
clusters involved, and NCSM effective interactions derived from
realistic interactions. In particular, we will present our first
results for the scattering of low-energy neutrons on $^4$He.
This work was performed under the auspices of the U. S.
Department of Energy by the University of California, Lawrence
Livermore National Laboratory under contract No. W-7405-Eng-48.
Support from U.S. DOE/SC/NP (Work Proposal Number SCW0498) is
acknowledged.\\ {\bf References }\\ 1. P.~Navr{\'a}til et al, Phys.
Rev. Lett. {\bf 84}, 5728 (2000);
Phys. Rev. C {\bf 62}, 054311 (2000).\\ 2. P.~Navr{\'a}til and W.~E.
Ormand, Phys. Rev. Lett. {\bf 88},
152502 (2002); Phys. Rev. C {\bf 68}, 034305 (2003).\\ 3. K.~Wildermuth
and Y.~C.~Tang , A Unified Theory of the
Nucleus., Vieweg, Braunschweig (1977). |
| |
| Ring, Peter |
Covariant density functional
theory and description
of excited states in nuclei far from stability |
| Covariant density functional theory is used to
describe excited states in nuclei far from stability. First we stay in
the concept of the mean field approximation and discuss new results
obtained in the framework of relativistic quasiparticle RPA (RQRPA) in
deformed nuclei. In particular we report on the E1-strength
distributions in chains of Ne and Mo isotopes, which have been
investigated recently at GANIL and in Rossendorf, and on low the lying
M1-strength in nuclei with large neutron excess. Besides the
conventional scissor mode, where protons and neutrons occillate against
each other, a new mode is found in these calculation, where the neutron
skin oscillates in a scissor like motion against the deformed core of
protons and neutrons moving in phase. In a second step we go beyond the
mean field approximation and discuss recent applications of the
relativistic Generator Coordinate Method (GCM) in transitional nuclei. |
| |
| Ringle, Ryan |
Towards a Penning Trap Mass
Measurement of {11}^Li |
| The halo structure of certain nuclei, such as
{11}^Li, is currently one of the most interesting phenomena observed
far from stability. It is not only interesting from a nuclear structure
point of view, but serves as an example of quantum behavior in a
microscopic few-body system, where some of its weakly bound components
tunnel beyond the binding potential of the core. Since the first
experiments in 1985 which implied a large matter radius, copious amount
of effort, both experimental and theoretical, has been expended in
understanding the halo nature of {11}^Li (and other halo nuclei). The
S_{2N} value of {11}^Li is a key ingredient in models attempting to
describe halo structure. The newly commissioned TITAN facility at
TRIUMF is ideal for making a Penning trap mass measurement of {11}^Li. |
| |
| Rodin, Vadim |
Recent developments in
calculations of nuclear double beta decay |
| Reliably calculated nuclear matrix elements
M$^{0\nu}$ for the neutrinoless double beta decay are crucial for
determining the absolute neutrino mass scale as well as for
distinguishing between possible mechanisms of the decay (exchange of
light and heavy neutrinos, SUSY particles, leptoquarks etc). In the
talk, recent calculation results of different nuclear structure models
are discussed. It is shown how an appropriate account of experimental
data helps to drastically reduce uncertainties in the calculations of
M$^{0\nu}$. |
| |
| Roth, Robert |
Ab-Initio Nuclear Structure
Calculations Beyond the p-Shell |
| The microscopic description of nuclei based on
realistic nuclear interactions is a supreme challenge for nuclear
structure theory. By starting from QCD-motivated realistic interactions
one expects reliable predictions also for nuclei far off stability.
These interactions, however, generate strong correlations in the
nuclear many-body state, which cannot be described by simple many-body
approximations. For p-shell nuclei, powerful ab initio tools like the
No-Core Shell Model or the Green's Function Monte Carlo approach are
available and have been employed successfully for nuclear structure
studies. In this context I will review and compare different methods
for deriving phase-shift equivalent effective interactions using
unitary transformations, e.g. the Unitary Correlation Operator Method
and the Similarity Renormalization Group. The extension of the domain
of ab initio schemes to nuclei beyond the p-shell is crucial for future
nuclear structure studies. I will discuss novel ideas to extend the
range of reliable ab initio calculations towards intermediate-mass
nuclei. Among those is an adaptive importance truncation of the no-core
model space based on an a priori estimate for the relevance of
individual basis states derived from perturbation theory. First
applications reveal the quality and efficiency of these methods. They
bridge the gap to approximate nuclear structure methods which, using
the same effective interactions, give access to the whole nuclear chart. |
| |
| Rubio Barroso, Berta |
β-decay properties of Tz=-1
nuclei. Future experiments at FAIR DESPEC |
| We are now performing interesting experiments on
the beta decay properties of Tz=-1 nuclei and its comparison with
mirror transitions observed in charge exchange reactions. At the same
time these series of experiments are used as a test bench for future
experiments at FAIR and more particularly at DESPEC (Decay
Spectroscopy) where I am the spokesperson. I think these topics nicely
fit in your programme. |
| |
| Sakurai, Hiroyoshi |
Nuclear Physics Programs with RIBF |
| I would like to show present status and coming
programs at the new facility of RIBF, through introducing recent
results obtained at the old facility. |
| |
| Schnack, Jürgen |
Modern Aspects in Magnetic
Structure and Dynamics |
| The physics of few-body quantum systems turns out
to be rather
universal. When changing from nuclei to magnetic molecules a lot
of old friends as for instance highly correlated ground states,
rotational modes (Yrast bands!) and phase transitions in small
systems will be met again. In the talk I will introduce some of
these concepts from a magnetic point of view. But there will of
course be time left for some good old memories ... |
| |
| Schuck, Peter |
Alpha-Particle Condensation in
Nuclear Systems |
| It is now quite well established that at least
the Hoyle state at 7.65 MeV in 12C has a wide extension where three
alpha particles move almost independently, all in 0S-wave orbital, hold
together only by the Coulomb barrier. It is very likely that analogous
states exist in heavier nuclei around the alpha-disintegration
threshold. First indications exist in 16O around 14 MeV. New
theoretical results shall be presented. For increasing number of
alpha-particles the Coulomb barrier fades away. Exciting 40Ca to the
alpha-threshold of about 60MeV via a HIC an alpha coherent state with
10 alphas may be formed with a certain probability which starts
expanding. Multiparticle detectors may identify the alphas.
Experimental studies are under way at IPN Orsay. Alpha-particle
condensation may exist in collapsing stars. The possibility of
quartetting and quartet condensation in other systems like cold atoms
shall be discussed. |
| |
| Schury, Peter |
A Multi-Reflection Time-of-Flight
Mass Spectrometer for Precision Mass Measurements of Very Short-Lived
Nuclei |
| The understanding of halo-nuclei, the region near
$^{42}$Si and the r-process pathway can be improved through precision
mass measurements of nuclei with T$_{1/2}<$30 ms. Mass measurements
of such very short-lived isotopes have thus far been limited to
relativistic single-pass time-of-flight spectrometers such as SPEG at
GANIL or the S800 at NSCL with typical relative mass uncertainties on
the order of $\delta$m/m$\approx$10$^{-6}$. While Penning traps provide
the highest possible mass precision, a low-energy multi-reflection
time-of-flight (MRTOF) mass spectrograph provides a more versatile
alternative. The RI Beam Factory (RIBF) at RIKEN will provide access to
very neutron rich nuclei at unprecedented intensities. In order to
perform precision mass measurements of these nuclei, an MRTOF mass
spectrometer is under construction as part of the SLOWRI facility at
RIKEN. The system is to be based on a small gas stopping cell and is
designed to be portable, allowing a powerful degree of flexibility to
maximize available on-line time for testing the device. By employing
extremely highly stabilized voltage supplies, as well as an advanced
ion preparation system, it is believed that relative precisions of
$\delta$m/m$>$10$^{-7}$ can be obtained with a series of 3 ms
measurements. Furthermore, such a system will be sufficiently sensitive
to provide precise mass measurements of nuclei with production rates of
perhaps as low as a few hundred per hour. |
| |
| Schwenk, Achim |
Three-nucleon interactions and
nuclear structure |
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| |
| Sorlin, Olivier |
Tensor and spin-orbit forces
viewed from the study of the N=28 shell closure. |
| The N=28 shell closure is the first arising from
the spin-orbit
interaction. Its evolution in nuclei with large
neutron to proton excesses is therefore potentially connected to that
of the spin-orbit interaction. From the doubly magic 48Ca to the close
to drip line 42Si nucleus, several structural modifications occur,
starting from spherical, prolate-spherical co-existence to oblate
shapes. Surprisingly a similar dramatic structural change does not
occur
for the N=20 isotones which remain remarkably spherical between the
40Ca and 34Si nuclei. By using up to date experimental data along the
N=28 isotonic chain, such as (d,p) transfer reaction, in-beam gamma-ray
spectroscopy, Coulomb excitation, isomeric transitions, the underlying
physics origin for
the profound structural modifications at the N=28 shell clsoure will be
emphasized. Among these, the action of tensor forces and the central
density dependence of the spin-orbit interaction will be commented. |
| |
| Tanihata, Isao |
Spectroscopy of drip line nuclei
with a thick target technique |
| The spectroscopy of exotic nuclei by transfer
reactions has limitation due to the intensity of a RI beam. It requires
a thick target to obtain a detectable amount of reaction first of all.
However, in usual method, a thick target can not be used because of the
energy loss of the low energy particles emitted from reactions. They
either stop in the target or loose considerable amount of energies in
the target and thus make the experiment impossible or the resolution
too bad to separate individual states. Active target is one of the
method to solve the problem. We show an experiment of 11Li(p,t)9Li
reaction at TRIUMF using an active target MAYA. Also the extension of
this method will be discussed for normal target geometry experiments. |
| |
| Tsoneva Larionova, Nadezhda |
Pygmy Dipole Response in Exotic
Nuclei in Multi-Phonon Representation. |
| Recently a theoretical method [1] incorporating
HFB calculations of the nuclear ground states and the QPM theory was
applied for investigations of low-energy dipole excitations in
spherical N=50, N=82 isotones and the $Z=50$ [2] isotopes. The analysis
of the corresponding neutron and proton dipole transition densities [2]
in these nuclei allows to assign a genuine pattern to the low-energy
dipole excitations - PDR modes and making them distinct from the
conventional GDR modes. From calculations limited to the one-phonon
QRPA approximation in all cases of N=50, N=82 and $^{110-132}$Sn nuclei
(N$>$Z) a close connection between the total neutron PDR strengths
and the neutron skin thickness defined by the
relative difference of neutron and proton rms radii was found. An
interesting observation is the most exotic $^{100}$Sn nucleus (N=Z),
where at E*=8.3 MeV a state with a proton structure was found. This
mode could be related to a proton PDR. Further development of the
multi-phonon QPM theory is performed for the study of the fragmentation
pattern of the low-energy dipole excitations, which can be achieved
within a large model configuration space including up to three-phonon
components. The reliable description of the experimental spectra is
discussed and compared to recent data.
[1] N. Tsoneva, H. Lenske, Ch. Stoyanov, Phys.\ Lett.\ {\bf B586}
(2004) 213 and refs. therein.
[2] N. Tsoneva, H. Lenske, arXiv:0706.4204Phys and refs. therein. |
| |
| Typel, Stefan |
Pseudospin, Supersymmetry and the
Shell Structure of Atomic Nuclei |
| The shell model is a cornerstone of nuclear
structure physics since
50 years. Nucleons occupy single-particles states in a mean-field
with strong central and spin-orbit components. The particular ordering
in energy leads to the appearance of prominent
shell gaps. Experimental observations suggest a change of the
shell structure and the appearance of new magic numbers in exotic
nuclei.
The effects of the spin-orbit potential and the tensor interaction
on the level structure have been discussed intensively in recent years.
In fact, the slope of the single-particle energies can provide
information on the monopole matrix elements of the effective
interaction entering in shell model calculations. It is important to
identify the contributions to the potential that are responsible for a
change in the level structure.
Single-particle levels defining the shell gaps are of particular
interest. In most cases they belong to a pair of pseudospin partners
that are almost degenerate in energy. A relativistic description seems
to provide a natural explanation for this phenomenon.
However, the symmetry-breaking potential in the relativistic
explanation is not really a suitable tool in estimating the pseudospin
breaking since it is not regular.
An alternative description of the degeneracy is obtained by applying
supersymmetric quantum mechanics. This approach is not limited to
relativistic models and a regular symmetry breaking potential is
obtained. |
| |
| von Neumann-Cosel, Peter |
Electron Scattering as a Tool to
Study Excited States with Unusual Features |
| I will discuss two examples of the power of
high-resolution electron scattering spectroscopy to unravel unusual
structures in light nuclei.
The first case discusses the first excited state 1/2+ state in 9Be. It
is unbound but just above the neutron trhreshold and thus shows an
asymmetric line shape. Determining its resonance properties is of
importance to estimate possible scenarios in supernovae, where 12C is
produced in an alternative route to the Salpeter process via
9Be(alpha,n). At present there is a conflict in the literature on the
correct resonance paremeters. I present new (e,e') experiments which
resolve the problem. Furthermore the form factor is compared to NCSM
calculations with large model spaces. The results indictae that this
weak E1 transition might violate the Siegert theorem. The second part
discusses the 0+ state at threshold in 12C (the Hoyle state). It is
known to be of alpa-cluster structure, but recently it was claimed to
possess a structure resembling a Bose-Einstein condensate. This claim
is critically investigated through electron scattering, which provides
information on the spatial structure of the Hoyle state. |
| |
| Wolter, Hermann |
Low-density symmetry energy |
| The symmetry energy at densities from below
saturation density down to very small values is important for the
structure of exotic nuclei and for astrophysical processes like
supernovae. I will discuss the results from attempts to gain
information from heavy ion collisions at Fermi energies from isospin
diffusion and migration. I will further discuss theoretical attemps to
determine the low density EOS in the framework of RMF theory under
contraints of neutron star observables, including many-body
correlations at very low density and the formation of heavy nuclei in a
neutron gas. |
| |
| Zaryouni, Saeedeh |
nuclear matter with Skyrme
potential |
| Nuclear matter is an idealized infinit uniform
system of nucleons under their mutual strong interactins.The equation
os state of nuclear and neutron matter has been studied by Skyrme
porential at Zero temperature by by Hartree -Fock approximation.We have
calculated asymetric energy and succeptibility of polarized neutron
matter.The results are in good agreement with other methods and
potentials. |
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