Monday, March 11, 2002 - DPG-Tagungen

Nuclear Physics Tuesday
HK 16.3 Tue 17:30 A
Spectral Function of Quarks in Quark Matter — •Frank
Frömel, Stefan Leupold, and Ulrich Mosel — Institut für
Theoretische Physik, Universität Gießen, Germany
We investigate the spectral function of light quarks in infinite quark
matter using a simple albeit self-consistent model. Relations between
correlation functions and collision rates are used to calculate the spectral
function in an iterative process. Similar calculations have already
been performed for nucleons in nuclear matter [1]. It was found there
that this approach reproduces the results of many-body theory using a
pointlike nucleon interaction with constant scattering amplitude. In our
calculations the interactions between the quarks are described by the
SU(2) Nambu–Jona-Lasinio model. We apply this method to calculate
the quark spectral function at zero temperature and finite chemical potential.
Work supported by DFG.
[1] J. Lehr, H. Lenske, S. Leupold, U. Mosel, nucl-th/0108008
HK 16.4 Tue 17:45 A
Chiral symmetry restoration and the Z3 sectors of QCD —
•Wolfgang Söldner, Christof Gattringer, P.E.L. Rakow,
and Andreas Schäfer — Institut für Theoretische Physik, Universität
Regensburg, D-93040 Regensburg, Germany
Quenched SU(3) lattice gauge theory shows three phase transitions,
namely the chiral, deconfinement and Z3 phase transition. Knowing
whether or not the chiral and deconfinement phase transition occure at
the same temperature for all Z3 sectors could be crucial to understand the
underlying microscopic dynamics. We find that the spectral gap opens
up at the same critical temperature in all Z3 sectors in contrast to earlier
claims in the literature.
HK 16.5 Tue 18:00 A
Thermal QCD on the Lattice: Quasiparticles And Confinement
— •Roland A. Schneider 1 and Wolfram Weise 1,2 — 1 Physik-
Department, Technische Universität München, Garching, Germany —
2 ECT*, Villazzano (Trento), Italy
We propose a novel quasiparticle interpretation of the equation of state
of deconfined QCD at finite temperature. Using appropriate thermal
masses, we introduce a phenomenological parametrization of the onset
HK17 Nuclear Physics / Spectroscopy II
of confinement in the vicinity of the predicted phase transition. Lattice
results of the energy density, the pressure and the interaction measure of
pure SU(3) gauge theory are excellently reproduced. We find a relationship
between the thermal energy density of the Yang-Mills vacuum and
the chromomagnetic condensate 〈B 2 〉T. Finally, an extension to QCD
with dynamical quarks is discussed. Good agreement with lattice data
for 2, 2+1 and 3 flavour QCD is obtained. We also present the QCD
equation of state for realistic quark masses. Applications to dilepton
production in heavy-ion collisions are outlined. Published in Phys. Rev.
C64 (2001) 055201.
Work supported in part by BMBF and GSI.
HK 16.6 Tue 18:15 A
Kaons in nuclear matter — •Thomas Roth, Michael Buballa,
and Jochen Wambach — Institut f. Kernphysik, TU Darmstadt
We investigate the modification of Kaons in isospin symmetric and
non symmetric nuclear matter. Using the leading s-wave couplings of
the SU(3) chiral meson-baryon Lagrangian we solve the coupled channel
Kaon-nucleon scattering equation selfconsistently.
We obtain a description of the in medium properties of the Kaonnucleon
scattering amplitude dominated by the Λ(1405) resonance. The
in-medium Kaon propagator is calculated for different densities and different
proton-neutron mixtures.
While the Λ(1405) resonance is little affected by increasing density, we
find that the Kaon mass experiences a strong downward shift. This will
be important for the concept of Kaon condensation in neutron stars.
HK 16.7 Tue 18:30 A
Alpha Cluster Condensation in 12 Cand 16 O — •G. Röpke 1 , A.
Tohsaki 2 , H. Horiuchi 3 ,andP. Schuck 4 — 1 FB Physik, Universität
Rostock, D-18051 Rostock, Germany — 2 Department of Fine Materials
Engineering, Shinshu University, Ueda 386-8567, Japan — 3 Department
of Physics, Kyoto University, Kyoto 606-8502, Japan — 4 Institut de
Physique Nucleaire, F-91406 Orsay Cedex, France
Anewα-cluster wave function is proposed which is of the α-particle
condensate type. Applications to 12 Cand 16 O show that states of low
density close to the 3 and 4 α-particle thresholds in both nuclei are possibly
of this kind. It is conjectured that all self-conjugate 4n nuclei may
show similar features.
Time: Tuesday 16:45–18:45 Room: B
Group Report HK 17.1 Tue 16:45 B
Peculiar Properties of Deformed Odd-Odd N = Z Nuclei —
•Alexander Lisetskiy, N. Pietralla, K. Jessen, I. Schneider,
A. Schmidt, andP. von Brentano — Institut für Kernphysik, Universität
zu Köln, D-50937 Köln, Germany
The near degeneracy of the states with total isospin quantum numbers
T =0andT = 1 in odd-odd N=Z nuclei and very strong magnetic
dipole (M1) transitions between them [1,2] are among the most interesting
phenomena observed in N = Z nuclei. Furthermore the nuclei
along the N = Z line offer a possibility to estimate the isospin mixing
in the low-lying states from electromagnetic transition strengths. In the
present work we analyze recent data and theoretical results on the structure
of the odd-odd N=Z nuclei 46 V, 50 Mn, and 54 Co [1-4]. New data in
combination either with the full pf-shell model or with collective rotorplus-quasideuteron
model results help to establish systematic regularities
for isovector M1 transitions, to reveal collective band structures in deformed
odd-odd N = Z nuclei 46 Vand 50 Mn, and to estimate the small
isospin mixing (0.4 %) between low-lying states with T =1andT =0
in the odd-odd N = Z nucleus 54 Co.
[1] A. F. Lisetskiy et al., Phys. Rev.C60, 064310 (1999).
[2] A. F. Lisetskiy et al., Phys. Lett. B 512, 290 (2001).
[3] I. Schneider et al., Phys.Rev.C61, 044312 (2000).
[4] N. Pietralla et al., Phys. Rev.C65, in press (2002).
Group Report HK 17.2 Tue 17:15 B
High-accuracy mass measurements on N = Z nuclei using
ISOLTRAP — •Frank Herfurth 1 , F. Ames 2 , G. Audi 3 , D.
Beck 4 , K. Blaum 4 , G. Bollen 5 , A. Kellerbauer 1 , H.-J. Kluge 4 ,
D. Lunney 3 , R.B. Moore 6 , D. Rodrígez 4 , E. Sauvan 1 , C.
Scheidenberger 4 , S.Schwarz 5 , G. Sikler 4 , C. Weber 4 ,andthe
ISOLDE-Collaboration 1 — 1 CERN, Geneva — 2 LMU, Munich
— 3 CSNSM, Orsay — 4 GSI, Darmstadt — 5 NSCL, East Lansing —
6 McGill Univ., Montreal
ISOLTRAP is a Penning trap mass spectrometer installed at the online
mass separator ISOLDE at CERN/Geneva. It serves for highaccuracy
mass measurements of radioactive nuclides by determining their
cyclotron frequency. After high-accuracy mass measurements on 74 Rb,
74 Kr and 34 Ar, the mass of 32 Ar was measured recently. A relative uncertainty
below 10 −7 was reached despite the short half-life of only 98 ms.
This mass value is needed in the context of the search for scalar contributions
to the standard model of weak interactions [1]. The experimental
QEC value for the 32 Ar superallowed β decay has now the required uncertainty
of only a few keV. 72 Kr is one of the two waiting point nuclei that
define the speed of the astrophysical rp-process beyond A = 64. Among
other things, its mass is an important input for the correct understanding
and modeling of the rp-process in this region. The mass of 72 Kr was
measured with a relative uncertainty of about 10 −7 .
[1]E.G.Adelbergeret al., Phys. Rev. Lett. 83, 1299 and 3101 (1999)
.