Sessions - DPG-Tagungen

Nuclear Physics Tuesday
excited 2 + state, but deviations are found to be large within the IBM.
In a second approximation an inclusion of the B(E2) strengths of the
2 + γ (in a vibrator the two-phonon 2 + ) state lead to an accuracy of the
approximation within a few percent in the IBM. That means fitting a two
parameter Hamiltonian to data, the value of K approx
3 corresponds to the
value of K3 with an accuracy of a few percent. K3 and the corresponding
effective γ-deformation parameter are given for a collection of nuclei.
[1] V. Werner et al., Phys. Lett. B 521 (2001) 146.
∗ supported by the DFG under contract Br799/11-1
HK 16.7 Tue 17:30 A
First observation of the scissors mode decay to the γ-band in a
well-deformed nucleus ∗ — •V. Werner 1 , N. Pietralla 2 , M.W.
Ahmed 3 , P. von Brentano 1 , C. Fransen 1 , H. von Garrel 4 , U.
Kneissl 4 , C. Kohstall 4 , A. Linnemann 1 , S. Müller 5 , H.H. Pitz 4 ,
D. Savran 5 , M. Scheck 4 , F. Stedile 4 , A. Tonchev 3 , S. Walter 4 ,
H.R. Weller 3 , and Y. Wu 3 — 1 Institut für Kernphysik, Universität
zu Köln — 2 SUNY, Stony Brook, NY — 3 FELL, Dept. of Physics,
Duke University, Durham, NC — 4 Institut für Strahlenphysik, Universität
Stuttgart — 5 Institut für Kernphysik, TU Darmstadt
Various experiments on 164 Dy in the 80’s and 90’s left ambiguities
in the placement of some γ-transitions. Todays improved NRF setup
in Stuttgart allowed a reinvestigation with increased sensitivity. γ-rays
were observed in an experiment above the energy threshold of about 3
MeV of the scissors mode, while the corresponding lines were missing
when tuning the maximum energy of the incident photons just below
that energy. Another experiment was performed at the new NRF setup
[1] at the FELL at Duke University using an almost monochromatic and
totally polarized photon beam. The polarization allowed firm parity assignments,
and the well-defined energy ensured that one of the mentioned
γ-rays stems from a so far only presumed level at 3.1 MeV. While the
ground state decay of that level is unexpectedly weak, the observation
backs a placement of so far unobserved decays of the scissors mode to the
γ-band. Transition strengths are in agreement with IBM predictions.
[1] N. Pietralla et al., Phys. Rev. Lett. 88 (2002) 012502.
∗ supported by the DFG under Br799/11-1, Kn153/31-2, and Pi 393/1-2.
HK 16.8 Tue 17:45 A
Investigation of Shape Coexistence in 106 Cd — •A. Linnemann,
C. Fransen, J. Jolie, D. Mücher, and V. Werner — Institut für
Kernphysik, Universität zu Köln
Excellent examples of quasi-complete structures representing shape coexistence
have been observed during the last decade in the Cd-isotopes
e.g. ref[1]. These isotopes form a great test of shape coexistence as here
the intruder states have their lowest excitation energy (at mid shell) exactly
at the line of stability. This allows the unique possibility to study
the six even-even Cd isotopes in an complete way as possible. We have
studied recently the lightest stable of those, 106 Cd, using the reactions
104 Pd(α, 2n) 106 Cd, 105 Pd( 3 He, 2n) 106 Cd and the β-decay 106 Cd(p, n) 106 In
with the HORUS-Spectrometer at the Cologne FN-Tandem accelerator.
First results of the analysis will be presented.
[1] M. Kadi, N. Warr, P. E. Garrett, J. Jolie, S. W. Yates, Phys. Rev.
C68 (2003) 031306
HK 16.9 Tue 18:00 A
Search for Hyperdeformation in 126 Ba ∗ — •A.K. Singh 1 , A. Al-
Khatib 1 , A. Bürger 1 , P. Bringel 1 , H. Hübel 1 , A. Neußer 1 ,
G.B. Hagemann 2 , B. Herskind 2 , C.R. Hansen 2 , G. Sletten 2 , D.
Curien 3 , A. Maj 4 , A. Lopez-Martens 5 , A. Bracco 6 , P. Fallon 7 ,
and B.M. Nyakó 8 for the EUROBALL collaboration — 1 HISKP, Univ.
Bonn, Germany — 2 NBI, Copenhagen, Denmark — 3 IReS, Strasbourg,
France — 4 IFJ, Krakow, Poland — 5 CSNSM, Orsay, France — 6 Univ.
Milano, Italy — 7 LBNL, Berkely, USA — 8 ATOMIKI, Debrecen, Hungary
A previous search for hyperdeformation in 126 Ba using the GAMMA-
SPHERE array at Berkeley led to the observation of a narrow ridge
structure in the γ-ray continuum corresponding to rotational bands with
a large moment of inertia. This motivated us to search for hyperdeformation
with the EUROBALL spectrometer at IReS, Strasbourg. Two
experiments were performed using the 64 Ni + 64 Ni reaction at beam
energy of 255 and 261 MeV. The first experiment was performed with
EUROBALL in combination with the large volume BaF2 detector array
HECTOR to measure GDR transitions between the highly deformed
states. The second experiment was done in combination with the charged
particle detector DIAMANT for a better selection of reaction channels.
The search for hyperdeformed structures both in the continuum and in
the discrete γ-ray spectrum is going on. So far no convincing discreteline
bands with appropriate statistical significance have been found. ∗
Supported by BMBF (06 BN 907), (Hu 325/10) and EU
HK 16.10 Tue 18:15 A
Microsecond Isomers in the Heavy Indium Isotopes — •A.
Scherillo 1,2 , J. Pinston 3 , J. Genevey 3 , G.S. Simpson 2 , H.
Faust 2 , and J. Jolie 1 — 1 Insitut für Kernphysik, Universität zu Köln,
Köln, Germany — 2 ILL, Grenoble, France — 3 LPSC, Grenoble, France
To extend our knowledge on the structure of the heavy Indium isotopes,
which is very scarse, their microsecond isomers were investigated.
These nuclei were produced by thermal-neutron-induced fission of 239 Pu
and 241 Pu, and separeted using the LOHENGRIN spectrometer at ILL
(Grenoble). The detection system was based on the time correlation
between the incoming fission fragment and the γ-rays or conversion electrons
emitted by the isomer. The decay schemes of the new yrast isomers
in 129,128,127,125,123 In are presented. The experimental results were found
to be in good agreement with a semi-empirical shell model calculation. A
truncated configuration space was used, including only the orbitals πg9/2
for the protons and νs1/2, νd3/2 and νh11/2 for the neutrons. The twobody
matrix elements of the residual interaction were extracted, wherever
possible, from experimental data.
This work was supported by ILL and by the BMBF under research
grant 06K-167/TP2.
HK 17 Electromagnetic and Hadronic Probes II
Time: Tuesday 15:30–18:30 Room: B
Group Report HK 17.1 Tue 15:30 B
New opportunities for hadron physics with the planned PANDA
detector — •james ritman for the panda collaboration — II Phys.
Inst. Univ. Giessen
One of the main components of the approved GSI Future Facility is a
high energy storage ring (HESR) that provides antiproton beams with
unprecedented intensity and momentum definition for beam momenta
between 1.0 and 15 GeV/c. Experiments with internal hydrogen and
nuclear targets will be performed with the PANDA (Pbar ANnihilation
experiemnt at DArmstadt) detector. The questions addressed include
the search for exotic QCD states (glueballs and hybrids), precision spectroscopy
of charmonium states, the properties of charm hadrons in nuclear
matter, and high resolution spectroscopy of (double) hypernuclei.
This talk will provide an overview of the design parameters and simulation
results of the detector facility envisioned to pursue the experimental
program.
Group Report HK 17.2 Tue 16:00 B
First measurements of transverse spin asymmetries at
COMPASS — •Richard Webb 1 , Jens Bisplinghoff 2 , Franco
Bradamante 3 , Wolfgang Eyrich 1 , Horst Fischer 4,5 , Rainer
Joosten 2 , Anna Martin 3 , and Paolo Pagano 3 for the COMPASS
collaboration — 1 Physikalisches Institut, Friedrich-Alexander-
Universität Erlangen-Nürnberg — 2 Helmholtz-Institut für Strahl- und
Kernphysik, Universität Bonn — 3 Università degli Studi and INFN,
Trieste — 4 Albert-Ludwigs-Universität Freiburg — 5 CERN, Geneva
COMPASS is a fixed target experiment on the SPS M2 beamline at
CERN. Its 6 LiD target can be polarised both longitudinally and transversally
with respect to the polarised 160GeV µ + beam. Approximately 20%
of the beam-time in 2002 and 2003 was spent in the transverse configuration.
The analysis of semi-inclusive deep inelastic events in transverse
mode opens up a number of channels to investigate the transverse quark
distribution function ∆Tq(x) and its associated structure function h1.
One of these is the azimuthal asymmetry in single pion production, the
so-called Collins effect. During the 2002 beam time COMPASS collected
approximately 1.2 · 10 7 tranversely polarised SIDIS events, enabling a