Seminars in 2010:
Tuesday 14th December
R. Yarmukhamedov (Uzbekistan Academy of Sciences, Uzbekistan)
Three-body Coulomb effects in the peripheral one-charged particle transfer reaction
Within the strict three-body (a,b and g) model, an influence of the three-body Coulomb
effects on different forms of the DWBA amplitude for the peripheral one-charged
particle transfer reaction a +(bg) --> b + (ag) being astrophysical interest is discussed.
It is shown that from the exact three-body distorted wave amplitude, the part can be
separated in which the contribution of the three-body Coulomb dynamics in the transfer
mechanism of the transition operator is taken into account correctly. Within the three-body
approach combining the dispersion method and the DWBA approach, the result of
estimation of contribution of the three-body Coulomb dynamics of the transfer mechanism
to the peripheral partial wave amplitudes for proton transfer reactions being astrophysical
interest are presented. The way of the correct account of three-body Coulomb dynamics
in the modified DWBA approach, which involves all possible subsequent Coulomb
re-scattering of three (a,b and g) particles in the transfer mechanism and results in the
renormalization of the dominant peripheral partial amplitude, is considered. The peripheral
transfer reaction with formation of the unbound resonant state for the residual nucleus
(ag)
is also discussed.
Tuesday 7th December (slides) J.
Cseh (Institute of Nuclear Research, Deberecen, Hungary)
Shape isomers and clusterization in atomic nuclei
discussed by applying symmetry-adopted methods. 36Ar is considered as a
specific example. In this nucleus the superdeformed band is known
experimentally, and is understood from the joint conclusion of many different
theoretical calculations. The hyper-deformed state, as well as the reaction
channels to populate it, was predicted from cluster studies. Recent experimental
data seem to justify these predictions.
Tuesday 30th November 2010 (slides)
Vittorio Somà (Service de Physique Nucléaire CEA Saclay, France)
Nuclear matter properties from self-consistent Green's functions methods
The equation of state of nuclear matter is of great importance in the
interpretation of heavy-ion reactions and a crucial ingredient in many
astrophysical models. Ab-initio calculations of thermodynamic properties i
n symmetric nuclear matter and neutron matter, performed within the
self-consistent Green's function method, are presented up to temperatures
of 20 MeV and for several densities. Short-range correlations induced by
the repulsive core of nucleon-nucleon interactions are taken into account
in the in-medium T-matrix. Different bare potentials are employed together
with the semi-microscopic Urbana three-body forces. The saturation properties
are correctly reproduced. While the pressure is sensitive to the inclusion of
three-body forces, the entropy is not. The unstable spinodal region is
identified and the critical temperature associated with the liquid-gas phase
transition is determined. When three-body forces are added a strong reduction
of the critical temperature is found, with a value of 12 MeV.
Tuesday 23rd November 2010 (slides)
W.Gelletly (University of Surrey)
Isospin for the Experimenter
Many of our experimental students know about Isospin because it is mentioned in
their undergraduate courses. In practice, especially if they are gamma-ray
spectroscopists working on heavy nuclei, they do not encounter it on a daily
basis. In this talk we will remind ourselves of the basis of the idea and why it is
important in Nuclear Physics. Examples will be given of its importance in many
types of study. The final example, which is based on our recent measurements
at GSI, will focus on how it helps us to combine measurements on beta decay
and charge exchange reactions to our advantage. Theorists and senior
experimenters are encouraged to come with examples of why it is important
in their work and I will try to leave time for this.
Tuesday 9th November 2010 (slides)
Jose Antonio Lay (University of Sevilla, Spain)
Dynamics of the scattering of 11Li on 208Pb at energies around
the Coulomb barrier
Reactions with loosely bound light nuclei and, particularly, halo and Borromean
nuclei have shown new specific reaction mechanisms. Long range absorption,
coupling to the continuum, and dipole excitation are essential in the
understanding of these nuclei. In this direction the collaboration E1104
has measured the scattering of 11Li on 208Pb at energies around the Coulomb
barrier. This is part of a campaign of experiments aimed at understanding
the distinctive features found in the scattering of loosely bound nuclei
(6He, 7Li) on heavy targets. The use of a heavy target provides a strong
electromagnetic field which highlights the enhanced polarizability of this
nuclei due to the strong coupling to its continuum. The theoretical study of
this reaction also provides important challenges such us the proper description
of the three-body structure of 11Li (for both the ground and continuum states),
and a accurate understanding of the reaction dynamics. In the latter case,
we discuss the accuracy and applicability of a simplified two-body di-neutron
model for this projectile, and the possibility of performing full four body
Continuum Discretized Coupled Channels calculations for the reaction.
Tuesday
2nd November 2010 (slides)Daniel Watts (University of Edinburgh)
EM probes - from nuclei to flux tubes
Recent work using intense electromagnetic beams to study the nature of strongly
interacting matter will be presented and discussed. Topics will include detailed
studies of the structure of heavy nuclei, the nucleon and mesons. The next
generation of experiments aiming to understand the nature of the flux tube
confining the quarks within the nucleus will be discussed, with particular
focus on new UK led ideas to exploit nuclear spectroscopy.
Tuesday
26th October 2010 (slides)Ian Cullen (University of Surrey)
A study of neutron rich isomers and masses using a storage ring
The fragmentation of 238U has been used to populate neutron-rich nuclei
in the A~190 region of the nuclear chart. Using the FRagment
Separator-Experimental Storage Ring (FRS-ESR) set up at GSI, the nuclei
created were stored and the mass of both ground and isomeric states
measured with an average accuracy of 51keV. Presented will be details of
both the experimental and analysis technique together with the masses
measured and their physical interpretation.
Tuesday
19th October 2010 (slides)N.J.Stone (Oxford University and University of Tennessee, Knoxville)
Short-lived excited state g-factor measurements with Radioactive Ion Beams
[RIBs]: new opportunities and limitations of the Recoil-in-Vacuum (RIV) method.
g-factor measurements give valuable information concerning the composition of
nuclear state wavefunctions, sensitive to both single particle and collective
components. The establishment of reliable methods for g-factor study with weak
RIB s is highly desirable. The demonstration of the RIV method, applied to the
2.6 ps 2+1 excited state in a RIB of 132Te, yielding |g| = 0.35(5) nm,
indicated that this relatively neglected method has an important role with
RIBs [1].
The RIV method measures the attenuation of the angular distribution of
de-excitation gamma transitions from aligned short-lived states populated
by Coulomb excitation, caused by precession about randomly oriented ionic
hyperfine fields. The initial degree of alignment can be reliably calculated
using well established codes and the distributions are, in many cases, highly
anisotropic, so that data of only moderate statistical quality are needed
to give a useful result, albeit only of the magnitude of the g-factor.
Report will be given of new a-priori calculations of the fields acting at
nuclei in electron states of a wide range of lifetimes in multiply charged
recoiling ions. These calculations model the physics of the precession process,
including precession frequencies and the probability of changing electron
states during the nuclear lifetime, using the best currently available
self-consistent multi-electron state theory.
Experimental possibilities to extend g-factor studies, with useful precision,
to excited states populated in fission and other nuclear reactions will be
outlined.
[1] N.J.Stone et al., PRL 94, 192501 (2005)
Tuesday
12th October 2010 (slides)Dr Jirina Stone (University of Tennessee / University of Oxford)
Equation of State of High Density Matter
Over the last decade, new observational information concerning compact
stars has provided evidence to challenge our understanding of the
fundamental properties of matter under extreme conditions. The new
generation of space observatories provides important data on thermal
emission from isolated neutron stars, their cooling history and their
radii. The number of known binary pulsars was considerably increased
due to improvements in radio telescopes and interferometric techniques
allowing extremely precise neutron star mass measurements. New data on
bursting millisecond pulsars, kHz quasi-periodic oscillations and half-day
long X-ray super-bursts are waiting for interpretation. New detectors of
gravitational waves are being built, offering exciting prospects for
new discoveries.
Microscopic physics of stellar matter is extremely challenging,
limited mainly by our still inadequate knowledge of the forces acting
between its constituents. Many theoretical models, based on very
different physical assumptions, have been developed, giving a
tantalizing variety of predictions of properties of symmetric and pure
neutron nuclear matter, such as the density dependence of the energy
per particle and of the symmetry energy. Predicted properties of neutron
stars, such as gravitational mass and radius, also vary widely. A
large number of these results are broadly consistent with existing
observations. However, it is impossible at present to choose a model
(or a class of models) which yield predictions of neutron star properties
reliable enough to lead observations in their search for significant data
leading to new physics.
In this talk, we give a brief survey of the existing status of nuclear
matter models and introduce a new, quark-model-based free nucleon- nucleon
interaction, the Oxford potential. Applications of the potential to free
nucleon-nucleon scattering data (phase shifts, 1S0 scattering length and
effective range) and the properties of the deuteron will be shown to be
in a very good agreement with experimental data. Finally, the equation
of state of symmetric and asymmetric nuclear matter in the
Brueckner-Hartree-Fock approximation will be discussed together with
its application in cold non-rotational neutron star models.
Tuesday 5th October 2010 (slides)
Dr Rayner Rodriguez (CSIC, Madrid, Spain)
Microscopic description of nuclear shapes with global energy density
functionals.
In this talk we will discuss recent microscopic studies, based on both Gogny
and Skyrme nuclear energy density functionals (EDFs), concerning the evolution
of the nuclear shapes in regions of the nuclear chart characterized by the
competition between different low-lying configurations based on different
intrinsic mean field deformations. In particular, we will pay attention to
the evolution of the nuclear shapes in Hf, Y, W, Os and Pt nuclei with neutron
numbers N=110-122. Additionally, we will also discuss recent HFB studies
on the evolution of the nuclear ground and low-lying one-quasineutron
configurations in neutron-rich Sr, Zr and Mo nuclei and show that our
calculations predict a remarkable connection between deformation effects
and the available data for charge radii in these nuclei.
Thursday 26th August 2010
Gopal Mukherjee (VECC Kolkata)
High spin
structure of near spherical nuclei near N, Z = 82
I shall discuss about our recent results on the high-spin
structures of nuclei near the
neutron magic number N = 82 in the mass region A ~ 130 and also of the nuclei near
the proton magic number Z = 82 in the mass region A ~ 190. The systematics of the
structure of nuclei in isotopic and isotonic chains will be discussed. It will be shown,
in the light of our recent results in these two regions, the onset of the dominance of
the Z = 50 gap in the structure of N = 79 isotones, and the onset of deformation for
the Z = 83 isotopes.
In the beginning I'll briefly talk about the existing and
upcoming experimental facilities
at the Variable Energy Cyclotron Centre, Kolkata. The National gamma-ray spectroscopic
facilities in India, which have been used in our investigation, will also be discussed
in brief.
Tuesday 13th July 2010
Raquel Crespo (IST, Lisboa, Portugal)
Resonant and non-resonant breakup of halo nuclei on a proton target
The reaction theory is a key tool to interpret experimental measurements and extract
nuclear structure information.
When describing the scattering of halo nuclei from a stable target it is crucial to handle
its few-body character. In addition, it is necessary to treat all opening channels (elastic,
inelastic, transfer and breakup) in equal footing. Recently a great deal of theoretical effort
has being made in developing few-body multiple scattering reaction frameworks and in
particular the microscopic few-body Faddeev/AGS framework [1, 2].
We analise recent experimental data on the breakup of the one-neutron halo 19C and 11Be
on a proton target at around 70 MeV/u [3, 4] using the AGS/Faddeev scattering framework
[5].
We aim to pin down the relevant physics that need to be incorporated in the reaction
mechanism in order to extract meaningful and accurate information from the data.
We dicuss current puzzles and shortcomings of the fewbody scattering approaches.
[1] L.D. Faddeev, Zh. Eksp. Theor. Fiz. 39, 1459 (1960) [Sov. Phys. JETP 12, 1014 (1961)].
[2] E.O. Alt, P. Grassberger, and W. Sandhas, Nucl. Phys. B 2, 167 (1967).
[3] Y. Satou at al, Phys. Lett. B 660 320.
[4] A. Shrivastava et al, Phys. Lett. B 596, 54 (2004).
[5] E. Cravo, R.Crespo, A.M. Moro, A. Deltuva, Rev. C 81, 031601, 2010
Friday 9th July 2010
Elizabeth Cunningham (University of Surrey)
The effect of spin-spin interactions on polarisation observables from
nucleon-nucleus scattering
With the next generation of radioactive beam facilities currently under construction
there is a vital need for nuclear reaction theory calculations to make predictions
of observables relevant to the proposed experiments. In order to do this for exotic
nuclear species, it is necessary to determine accurate optical models to describe nucleon
elastic scattering from non-zero target spin, I.
Inclusion of terms in the optical potential which depend on the spin operator, I, of
the target nucleus, were first proposed by Feshbach over 50 years ago [1]. Initially
many attempts were made to describe these spin-spin interactions using a central or
so called spherical spin-spin term, sigma × I. Later works also included
a second-rank tensor spin-spin term with the operator, S12 = 3(sigma ×r)(I × r) –sigma × I.
The effects of these terms have since been the subject of much theoretical and experimental
interest, but it was not until the work of McAbee [2] that a generalised spin-spin
tensor was proposed.
In this work we evaluate the generalised spin-spin tensor within the DistortedWave
Born Approximation and apply it to proton scattering from 10B, for which relevant IUCF
data exist. The effect on spin observables, specifically the polarisation transfer coefficient
DNN will be presented.
[1] H. Feshbach, Ann. Rev. Nucl. Sci. 8 (1958) 49
[2] T. L. McAbee, W. J. Thompson, H. Ohnishi, Nucl. Phys. A509 (1990) 39
Tuesday 6th July 2010
Pavel Detistov
(Bulgarian Academy of Sciences, Institute of Nuclear Research and Nuclear Energy, Sofia)
Simulations of the RISING and AGATA detector arrays for relativistic heavy ion beams experiments
The experiments with relativistic secondary beams are powerful tool for studying the nuclear structure
far from stability. In such experiments the performance of the detector systems is strongly influenced
by the background radiation having atomic origin. Such experiments have been done in the framework
of the RISING project. The detector array consisted of up to 15 highly efficient HPGe cluster detectors
arranged in three different campaigns with three deferent detector geometries of the setup - “fast” beam
setup, “stopped” beam setup and g-Rising setup. The AGATA project is the European project for
construction of the highly segmented HPGe array employing the gamma-ray tracking technique.
Each AGATA cluster consists of 3 36-folded HPGe crystals. The total 4-pi array will consists of 60
triple clusters. It is planned that AGATA will be used in fast beam experiments at the GSI facility in
2011-2012. Using the GEANT4 simulation tool, a model for simulating the atomic background radiation
has been developed. The prompt radiation was simulated for several types of experiments using
different detection systems, such as stopped- and fast-beam RISING and fast-beam AGATA. The
origin of the atomic radiation, the simulations and obtained results will be presented.
Monday 28th June 2010
Mark Alford (Washington University in St. Louis)
Quark matter in neutron stars
The densest predicted state of matter is color-superconducting quark matter, which has some affinities
to electrical superconductors, but a much richer phase structure because quarks come in many varieties.
This form of matter may well exist in the core of compact stars, and the search for signatures of its
presence is currently proceeding. I will review the nature of color-superconducting quark matter, and
discuss some ideas for finding it in nature.
Friday 25th June 2010
Yoritaka Iwata (GSI Helmholtz Center, Darmstadt, Germany)
Many-body collective dynamics in heavy-ion collision - mechanism of charge equilibration and
a unified description of nucleon transfer
Nowadays, microscopic three-dimensional time-dependent Hartree-Fock (TDHF) calculations are
feasible with Skyrme-type effective interactions. Based on the TDHF theory, the crucial contribution
of collective dynamics to low-energy heavy-ion collisions is clarified. We first discuss the mechanism
of charge equilibration. Next, a challenge towards the unified description of nucleon transfer
is shown, which microscopically gives a simple explanation for the reason why the proton-richness
does not necessarily result in the enhancement of proton transfer contrary to the neutron-richness
in neutron transfer.
Thursday 24th June 2010
Sait Umar (Vanderbilt University, USA)
Microscopic Study of Ion-Ion Potentials based on TDHF
The density-constrained-TDHF method is a fully microscopic theory for calculating heavy-ion interaction
potentials and fusion cross sections. The method is based on the TDHF evolution of the nuclear system
coupled with density-constrained Hartree-Fock calculations. A new method for calculating the dynamical
excitation energies will also be presented. We will discuss applications to fusion reactions
(64Ni+132Sn, 64Ni+64Ni, 16O+208Pb) and to systems leading to superheavy formations (70Zn+208Pb,
48Ca+238U).
Tuesday 8th June 2010
Akram Mukhamedzhanov
(Cyclotron Institute, Texas A&M University)
Gravitational interaction of nucleons with mini black holes.
I analyze the interaction of the nucleons with mini black holes (MBH).
MBH are hypothetical objects having enormous mass density. The mass of the MBH (in g) can
be estimated from equation M = 6.74 x 10^{27} R g , where its radius R is expressed in cm.
For example, for R = 10^{-13} cm we get M = 6.74 x 10^{14} g.
Such a gigantic mass curves the space around. In this talk I consider the gravitational
interaction of the MBHs with non-relativistic nucleons. Evidently that requires derivation
of the equation for the wave function in a curved space. To do it I start from the Klein-Gordon
equation, which is written in the covariant form in the general relativity. The Schwarzschild metric
tensor is the most common used, but its spatial part has singularity at r = r_s , where r_s is the
Schwarzschild radius. To remove this singularity I use the Eddington-Filkenstein metric tensor.
Writing down the Klein-Gordon equation in the Eddington-Filkenstein metrics and taking
the nonrelativistic limit I get the Schrodinger equation in the curved space created by the MBH.
The interesting feature is that the curved space generates an imaginary potential responsible
for absorption of the matter by the MBH. After that I calculate the mass gained by the MBH when
it passes, for example, through sun. I conclude that the MBHs are not dangerous and rumors about LHC
collider are not justified.
Tuesday 1st June 2010
Rick Casten
(Yale University)
New correlations of nuclear observables and approaches to extrapolation
in the exotic beam era
Wednesday 19 – Friday 21 May 2010
Workshop on Nuclear Isomers: Structure and Applications
Details and files of the presentations are available.
Tuesday 18th May 14.00 2010
Carl Wheldon
(University of Birmingham)
Hefeweizen and state-by-state tagging
The Munich Q3D spectrometer can deliver resolutions down to 2 keV at the focal plane
for reactions involving light ejectiles. Two new set-ups have been developed to exploit
this capability, involving the integration of double-sided silicon-strip and germanium
detectors at the target position. Coincident events, gated by the initial state populated
in the recoil, can now be used to measure, for example, alpha decay widths.
The first results from this project will be presented.
Tuesday 11th May 2010
Dr (National Nuclear Laboratory)
Nuclear Energy: Next Generation of Reactors
The Government's Energy Review has highlighted the role nuclear energy can play in delivering
a sustainable energy mix for the UK. Nuclear has come back into the equation given concerns
over increase in oil and gas prices, rising CO2 emissions, the potential for blackouts, fossil
fuel imports and uncertainty over renewable sources. However, against this backdrop nuclear
energy generating capacity will decrease significantly over the next decade as many stations
come off line and the timeframe for new nuclear build is tight.
This presentation provides an overview of the potential role nuclear energy could play, the
technologies available and the reactor systems that are being considered. It also covers
where nuclear energy research is heading and more advanced nuclear reactor systems that
could be deployed in the future.
Tuesday 4th May 2010
G. D. Dracoulis (Department of Nuclear Physics, R.S.P.E., ANU, Canberra, Australia)
Links Between High-K and Low-K States in 176Lu and 180Ta
Nature's heaviest naturally occurring odd-odd isotopes, 176Lu and 180Ta have a pair of high and
low-K levels at low energies formed by parallel or anti-parallel coupling of the unpaired proton
and neutron to give a total projection, K = | Omega_ p +- Omega_n |.
One manifestation of this is the formation of a long-lived 9- isomer in 180Ta, the only naturally
occurring nuclear isomer, with a lifetime of tau_m > 1.2 x 1015 years, 77 keV above the
K^pi = 1+ short-lived ground state. The opposite situation occurs in 176Lu: it exhibits a long-lived
K^pi = 7- ground state and a 1- short-lived isomer at 123 keV. Both nuclei present issues for
nucleosynthesis; 180mTa in terms of its abundance, creation, and survival in stellar environments;
176Lu because, while definitely s-process (a possible s-process chronometer or thermometer),
it could be destroyed through neutron capture to the short-lived -decaying state while photon
excitation via intermediate-K states passing from the 1- level to the ground state or a transition
in the opposite direction, could either increase or decrease its abundance,
I will cover some new results from gamma-ray spectroscopy that bear on these issues, partly in
the context of the relationship between the strong resonances observed in laboratory photoactivation
(see, for example, Ref. [1]) and the problem of associating these resonances and their properties with
specific excited states.
1. D. Belic et al. Phys. Rev. C 65, 035801 (2002).
Tuesday 27th April 2010
Professor George Dracoulis (FAA, Australian National University)
Nuclear Power in Australia; On the Road with UMPNER
This lecture will outline the background and conclusions of the 2006/2007 review of the
Nuclear fuel cycle and its possible role in Australia, from uranium mining to electricity
generation. The presentation will cover aspects of uranium production, greenhouse gas
emissions from competing technologies, nuclear power world-wide, the predicted cost
of electricity generation in Australia, and some of the (serious and not so serious) issues
associated with waste, public perception and public acceptance.
Thursday 22nd April 2010
B. Fernandez-Dominguez (GANIL)
Spectroscopy of 21-O through the (d,p) reaction with the TIARA+MUST2+VAMOS+
EXOGAM set-up at GANIL
The single-particle structure of exotic nuclei seems to evolve with the isospin.
The well-established sequence of magic numbers appears to be modified as we
move away from the line of stability. In particular, the evolution of the d3/2
level is of paramount importance as the raising of this level will cause an enhancement
of the N=16 rather than the N=20 shell gap. One-nucleon transfer
reactions such as (d,p) selectively and directly probe the single-particle nature
of nuclear levels. A campaign of experiments performed in GANIL with
the TIARA+MUST2+VAMOS+EXOGAM set-up aimed to study the singleparticle
structure of exotic nuclei in the N=16 region. We report here on the
preliminary results of the {20}O(d,p){21}O reaction. The main goal of the experiment
was to measure the single-particle strength in {21}O and to locate the so-far
unobserved 3/2+ state that carries the 0d3/2 strength. This state is predicted
above the neutron separation energy, hence the parameterisation of the reaction
mechanism is crucial in order to extract reliable l-value assigments and spectroscopic
factors. Special attention will be given to the parameters used in the
description of the scattering of weakly bound nuclei.
Monday 12th April 2010
Stephen F. Ashley (INP, NCSR Demokritos, Athens, Greece)
On Lifetime Measurements in 102Pd Pertaining to Critical Point Symmetries in Atomic Nuclei
Analytical solutions of the Bohr Hamiltonian, applied to the framework of the IBA, have yielded the
ability to map the characteristics of the potential along the vertices of the symmetry triangle [1,2].
Two critical points, denoting a change of phase between vibrational to gamma-soft rotation, X(5) [1],
and vibrational to rigid rotation, E(5) [2], have been identified. For both these critical points,
the associated potential is modelled as an infinite square-well and upon solving the Bohr Hamiltonian
with this potential, predictive level schemes and transition rates have been determined. For E(5)
symmetry, a systematic sweep of the table of isotopes yielded six potential candidates which may
purvey this critical-point symmetry [3]. These are 102Pd, 106Cd, 108Cd, 124Te, 134Xe and 138Ba.
This talk will focus on measurements performed at INFN Legnaro to determine the lifetimes of the
low-lying yrast states in 102Pd. A 92Zr(13C,3n)102Pd fusion-evaporation reaction, with E(13C) = 48 MeV,
was utilised to populate excited-states in 102Pd. The 92Zr target of ?1mg/cm2 was mounted inside
the Koln coincidence-plunger apparatus [4], with a ?4mg/cm2 197Au stopper. This stopper was mounted
on a piezoelectric motor and twenty-five separate target-stopper distances were made during this
measurement. Reaction gamma-rays were detected using the GASP array consisting of forty
Compton-suppressed HPGe detectors. Subsequent off-line analysis of the coincidence gamma-rays
was performed and by applying the Differential Decay Curve Method [5,6], the lifetimes for
the 2+, 4+ and 6+ states in 102Pd have been determined. Furthermore, lifetimes for various
medium-spin collective transitions, within the picosecond regime, have also been determined.
Comparison of these results to the proposed E(5) level scheme will be presented as well as
comparisons to MAVA QRPA calculations [7]. Further work, utilising Coulomb-excitation and
inelastic proton scattering at NCSR Demokritos will be discussed.
[1] F. Iachello, Phys. Rev. Lett. 87 (2001) 052502
[2] F. Iachello, Phys. Rev. Lett. 85 (2000) 3580
[3] R.M. Clark et al., Phys. Rev. C 69 (2004) 064322
[4] A. Dewald et al., Nucl. Phys. A 545 (1992) 822
[5] A. Dewald et al., Zeit. fur Physik A 334 (1989) 163
[6] G. Bohm et al,. Nucl. Phys. A 329 (1993) 248
[7] J. Kotila, Priv. Comm.
Tuesday 30th March 2010
Thomas Duguet (CEA, Saclay)
Lowest-order contribution of the three-nucleon force
to pairing properties of nuclear ground-states
The nuclear Energy Density Functional (EDF) approach is used to study
medium-mass and heavy nuclei in a systematic manner. Currently used EDFs
provide a satisfactory description of low-energy properties of known nuclei. However,
their empirical character and the spreading of the results obtained from different
parameterizations, as one moves away from the valley of !-stability and enters
experimentally-unexplored regions, point to the lack of predictive power of today?s
calculations.
Our objective is to improve on such a situation by designing non-empirical
energy density functionals constrained explicitly from inter-nucleon interactions in
the vacuum. As a starting point, we have performed the first systematic finite-nuclei
calculations [3, 4, 5] using a nuclear EDF whose pairing part is built at first order in
low-momentum interactions [2] in the vacuum. The present contribution will focus on
new results obtained regarding the impact of the three-nucleon force and the Coulomb
interaction on pairing properties of nuclear ground states [6].
Tuesday 23rd March 2010
Nikolay Minkov (Institute of Nuclear Research and Nuclear Energy, Sofia)
Collective and single particle motion in nuclei with reflection asymmetry
Recently developed model approaches describing parity e?ects in the spectra of reflec-
tion asymmetric nuclei [1-4] will be presented. The interplay between collective and single
particle (s.p.) degrees of freedom in these nuclei will be discussed within a core plus particle
framework. The collective part of the model involves a two-dimensional potential providing
coherent oscillations of the system with respect to the axial quadrupole and octupole vari-
ables beta_2 and beta_3 [1]. It describes the parity shift effects in the spectra of even-even rare earth
nuclei [1] and reproduces the structure of split parity-doublet spectra in a wide range of
odd-mass nuclei [2]. The motion of the odd nucleon in the field of the quadrupole-octupole
deformed core in the odd-mass nucleus is described within a reflection-asymmetric deformed
shell model [3,4]. A strong coupling scheme between the parity mixed s.p. state and the
collective quadrupole-octupole mode in the core is considered [4]. The Coriolis decoupling
factor appears in a projected form corresponding to a good total parity of the system. The
average parity of the s.p. state and the decoupling factor are evaluated in various nuclei
as functions of the quadrupole and octupole deformation parameters beta_2 and beta_3. The be-
haviour of the calculated decoupling factors in the (beta_2;beta_3)-plane allows one to determine
physically reasonable regions of deformations in odd-A nuclei [4]. The possibilities for a
consistent collective and microscopic model description of reflection asymmetric nuclei will
be discussed on the above basis. The extension of the study to high spin isomeric states
with the presence of quadrupole-octupole deformations will be also discussed.
[1] N. Minkov, P. Yotov, S. Drenska, W. Scheid, D. Bonatsos, D. Lenis and D. Petrellis,
Phys. Rev. C, 73, 044315 (2006).
[2] N. Minkov, S. Drenska, P. Yotov, S. Lalkovski, D. Bonatsos and W. Scheid, Phys. Rev.
C, 76, 034324 (2007).
[3] N. Minkov, S. Drenska, M. Strecker and W. Scheid, J. Phys. G: Nucl. Part. Phys., 36,
025108 (2009).
[4] N. Minkov, S. Drenska, M. Strecker and W. Scheid, J. Phys. G: Nucl. Part. Phys. 37,
025103 (2010).
Tuesday 9th March 2010
Phil Woods (University of Edinburgh)
Experiments along the Borderline of Nuclear Astrophysics and Nuclear
Reaction/Structure Physics
The talk will explore the increasingly fertile territory overlapping the
fields of explosive nuclear astrophysics, and the structure and reactions
of exotic nuclei. It will be shown that a broad range of techniques involving
transfer reactions, gamma-ray spectroscopy and decay spectroscopy are
essential to understand explosive astrophysical events, such as novae,
X-ray bursters and supernovae. The talk will focus on recent and current
experiments being pursued/proposed at a range of facilities.
In many instances, it is proposed the results obtained will pose as many
challenges for nuclear physics as for nuclear astrophysics.
Tuesday 2nd March 2010
Alexis Diaz-Torres (University of Surrey)
Unambiguous modelling of complete and incomplete fusion of weakly bound nuclei:
a classical trajectory model with stochastic breakup
Low energy fusion reactions of nuclei far from stability are crucial for forming heavy
elements in the cosmos, which are being intensively investigated in different radioactive
isotope facilities worldwide. The most exotic of these are often very weakly bound, and
can easily breakup in their reactions with other nuclei. This reaction process may affect
the fusion process, as not all the resulting breakup fragments might be captured by the
target, termed incomplete fusion (ICF); capture of the entire projectile by the target is
called complete fusion (CF). Events where the projectile breaks up and none of the
fragments are captured provide an important diagnostic of the reaction dynamics. This we
call nocapture breakup (NCBU), which is expected to be predominant at energies below
the fusion barrier. The modelling of all these reaction processes within the same
theoretical framework is an outstanding problem. Continuum discretised coupled channels
(CDCC) quantum mechanical models can make reliable predictions of the NCBU
process and the total fusion (CF + ICF), but cannot distinguish between ICF and CF
processes [1]. In my talk I will introduce a classical trajectory model with stochastic
breakup [2] which allows one an unambiguous solution of this problem along with
asymptotic observables of the breakup process. This unique capability provides a
powerful tool for interpreting future fusion experiments with radioactive nuclei an in
applications to gamma ray spectroscopy.
Tuesday 23rd February 2010
Wilton Catford (University of Surrey)
Experimental and Theoretical perspectives on transfer: recent work at
SPIRAL and TRIUMF
Recent work on nucleon transfer at SPIRAL (using TIARA and MUST2 with EXOGAM)
and TRIUMF (using the new SHARC Si array with TIGRESS) has employed
radioactive beams of 20O, 26Ne and 25Na. The aims are to identify and measure
spectroscopic properties of states in the region where N=16 emerges as
a magic number rather than N=20 and N=28. In all of these cases, population
of both bound and unbound states in (d,p) is studied, and gamma-coincidence
data were recorded. The unbound states in 21O and 27Ne are of particular
interest, and we will need to devise ways to interpret their differential
cross sections. In the case of the 20O and 26Ne beams, the reactions (d,t)
and (p,d) were recorded simultaneously, in order to compare results with
neutron removal reactions at higher energies (including work by our group
performed at GANIL with SPEG and EXOGAM). The work with the 25Na beam was
at TRIUMF and includes extensive gamma-ray coincidence data that will be
utilised in new algorithms to isolate individual states that cannot be
resolved by particle means alone. A follow-up experiment to study 24Na(d,p)
at TRIUMF, for astrophysical reasons, has also been approved and will be
described.
Friday 19th February 2010
Hugo F. Arellano (Department of Physics - FCFM, University of Chile)
Unveiling angular correlations from particle-particle propagation
in symmetric nuclear matter
Within the framework of the Brueckner-Bethe-Goldstone theory for
infinite nuclear matter, angular correlations arising from particle-particle
propagation are disclosed. Their account follows an exact treatment
of the Pauli exclusion principle on intermediate states while the angular
structure of the energy denominator is retained. As a result, a correlation
form factor emerges from the Cauchy principal-value of the particle-particle
propagator, while the imaginary part becomes structurally different from
those in Lippmann-Schwinger-type equations. These features modify the behavior
of the mass operator near the Fermi surface, reshaping the phase-space where
its imaginary part vanishes. Implications of these effects on saturation
properties of infinite nuclear matter shall be discussed.
Tuesday 9th February 2010
Stefan Lalkovski (University of Sofia)
Fast timing with lanthanum bromide gamma-ray detectors
Tuesday 2nd February 2010
Yuri Litvinov (GSI)
Two-body beta decay of highly-charged ions
The ion storage-cooler ring ESR at GSI, Darmstadt, Germany coupled to a high-
energy synchrotron SIS and a fragment separator FRS, is a unique facility for ad-
dressing two-body beta decays of stored and cooled highly-charged ions, i.e. bound-
state beta decay and orbital electron-capture (EC). In such two-body beta decays,
the monochromatic (anti)neutrinos created in the electron-avour eigenstate are
entangled with the recoiling daughter ions by the energy and momentum conserva-
tion. In course of the very rst measurements of the EC decay probability of hydrogen-
like ions, it turned out that hydrogen-like 140Pr58+ and 142Pm60+ nuclides decay by
about 50% faster than the corresponding helium-like ions. It will be shown that this
result, albeit being somewhat surprising, can be understood within the framework
of standard nuclear physics theory.
By reducing the number of stored ions to about two, each single ion can be
continuously monitored with a time resolution of better than 100 ms. These exper-
iments were conducted with both, hydrogen-like 140Pr58+ and 142Pm60+ ions. The
time of each EC decay has been precisely determined. Several thousands of EC
decays have been recorded. Superimposed on the expected exponential decrease of
the number of EC decays as function of time, we observed a time modulation with
a period of about 7 seconds for both systems. The observed eect is meanwhile
broadly discussed in literature. Some scenarios show that our observations could
be attributed to the coherent creation of nite mass eigenstates of the electron
neutrino in these two-body weak decays. It will be shown how this hypothesis of a
special kind of "quantum beats" could be corroborated or disproved in other two-
body weak decays. The present status of the experiments and some preliminary
results will be presented.