Sessions - DPG-Tagungen

Nuclear Physics Tuesday
of centrality selected minimum bias data at 40 A·GeV. Furthermore, we
show the ¯ Ξ + /Ξ − ratio in dependence on collision centrality and beam
energy.
Finally, our results are compared to other measurements and model predictions.
HK 21.8 Tue 17:30 F
Rapidity and transverse momentum dependence of π-π Bose-
Einstein correlations measured at 20,30,40,80 and 158 AGeV
beam energy (Stefan Kniege, Christopher Alt, Dominik Flierl)
— •S. Kniege 1 , C. Alt 1 , C. Blume 1 , P. Buncic 1 , P. Dinkelaker
1 , D. Flierl 1 , V. Friese 2,3 , M. Gazdzicki 1 , M. Kliemant 1 , I.
Kraus 2 , B. Lungwitz 1 , C. Meurer 1 , M. Mitrovski 1 , S. Radomski
2 , R. Renfordt 1 , A. Richard 1 , A. Sandoval 2 , R. Stock 1 und
H. Ströbele 1 für die NA49-Kollaboration — 1 Institut für Kernphysik,
Universität Frankfurt — 2 Gesellschaft für Schwerionenforschung (GSI),
Darmstadt — 3 Fachbereich Physik der Universität, Marburg
The space time conditions during the last stages of a heavy ion collision
define the HBT radii. Within hydrodynamic inspired models these observables
are related to crucial parameters describing the dynamics of such
a collision. The dependence of the measured radii on transverse momentum
can be related to quantities like temperature, strength of transverse
expansion and life time of the fireball.
Various measurements at the SPS energy scan programme suggest a qualitative
change in several observables at 20-30 AGeV. We will present the
rapidity as well as the kt dependence of pion HBT radii at 20 and 30
AGeV recently measured by the NA49 experiment. The new results will
be compared to measurements at 40,80 and 160 AGeV beam energy.
HK 21.9 Tue 17:45 F
Ω − and ¯ Ω + production in central Pb+Pb collisions at SPS
energies ∗ — •M. Mitrovski 1 , C. Alt 1 , C. Blume 1 , P. Buncic 1 , P.
Dinkelaker 1 , D. Flierl 1 , V. Friese 2,3 , M. Gazdzicki 1 , M. Kliemant
1 , S. Kniege 1 , I. Kraus 2 , B. Lungwitz 1 , C. Meurer 1 , S. Radomski
2 , R. Renfordt 1 , A. Richard 1 , A. Sandoval 2 , R. Stock 1
und H. Ströbele 1 für die NA49-Kollaboration — 1 Institut für Kernphysik,
Universität Frankfurt — 2 Gesellschaft für Schwerionenforschung
(GSI), Darmstadt — 3 Fachbereich Physik der Universität, Marburg
Preliminary results on Ω − and ¯ Ω + production in central Pb+Pb
collisions at 30, 40, 80, and 158 A·GeV are presented.
These measurements are performed using the large acceptance NA49
hadron spectrometer at the CERN SPS which allows for precise
determination of particle momenta and decay topologies.
Fully corrected rapidity and mT spectra in central Pb+Pb collisions at
40 and 158 A·GeV are obtained. Also total multiplicities at 40 and 158
A·GeV are estimated. The yields at mid-rapidity agree closely with the
results of WA97/NA57[1]. The ratio of ¯Ω + /Ω − is calculated for central
Pb+Pb collisions at 30, 40, 80 and 158 A·GeV. This ratio is smaller than
1 for Pb+Pb collisions. The yield measured in central Pb+Pb collisions
at 158 A·GeV is close to the expectation of a hadron gas model[2]
(grand canonical approximation) with partial strangeness saturation.
∗ Supported by BMBF and GSI.
HK 22 Plenary Session
[1] E.Andersen et al. (WA97), Phys. Lett. B449 (1999) 401.
[2] F. Becattini et al., hep-ph/0310049 (2003).
HK 21.10 Tue 18:00 F
Interpretation of the system-size dependence of strangeness
production in A+A collisions at 158 AGeV — •C. Höhne 1 , F.
Pühlhofer 1 , I. Kraus 2 , M. Gazdzicki 3 , H. Ströbele 3 , and R.
Stock 3 for the NA49 collaboration — 1 Fachbereich Physik, Universität
Marburg — 2 GSI, Darmstadt — 3 Institut für Kernphysik, Universität
Frankfurt
New data from the NA49 experiment at the CERN-SPS support the
interpretation that in central Pb+Pb collisions above 30 AGeV a partonic
phase is created in the early stage of the reaction. This conclusion
is based on the non monotonic devolution of the energy dependence of
strangeness production. Complementary information is obtained from
the system-size dependence recently measured by NA49 (p+p, C+C,
Si+Si, Pb+Pb at 158 AGeV).
The data show a steep rise of the relative strangeness production as
a function of the number of participating nucleons reaching a saturation
value at Npart ∼ 60. Qualitatively, this scenario is expected from
statistical models in which the relative strangeness content rises with
increasing volume due to vanishing constraints imposed by strict local
flavor conservation. In this work an attempt is made to understand this
phenomenon starting from a microscopic view of the reaction. Using
results from model calculations the hypothesis is formulated that coherent
partonic subsystems of increasing size are formed decaying as one
quantum-mechanical object. Hadron abundances resulting from this decay
can be described with statistical models.
HK 21.11 Tue 18:15 F
Simulation studies of the future CBM experiment at GSI † —
•Romain Holzmann for the CBM collaboration — GSI, Darmstadt
The Compressed Baryonic Matter experiment (CBM) planned at the
future GSI accelerator facility SIS200 [1] will study heavy-ion collisions
in the energy range of 10–30 AGeV, exploring the phase diagram of nuclear
matter at maximum reachable densities, yet moderate temperatures.
The prime goals of CBM are the exploration of the phase boundary
close to the predicted tricritical point, as well as the study of inmedium
properties of hadrons. To this end, CBM is designed as a highacceptance,
high-resolution and high-rate detector for charged particles.
Among the sensitive experimental signals to be measured are low-mass
vector mesons (ρ, ω and φ), open charm (D + , D − , D 0 ), hidden charm
(J/Ψ) and multi-strange baryons. Most of these are very rare probes
and will need to be acquired both at very high event rates and with very
selective triggers. Detailed feasibility studies of the detector concept
have been started and will be presented. [1] Conceptual Design Report,
http://www.gsi.de/GSI-Future/cdr/
† supported by GSI, BMBF, INTAS and EU
Time: Wednesday 08:30–10:00 Room: P
Plenary Talk HK 22.1 Wed 08:30 P
Facets of the (d, 2 He) Charge Exchange Reaction at Intermediate
Energies: from NN-studies to astrophysics to doublebeta
decay — •Dieter Frekers — Inst. f. Kernphysik, Universität
Münster
In this talk, results from the (d, 2 He) reaction at intermediate energies
are presented. The unbound di-proton system is referred to as 2 He, if the
two protons couple to a 1 S0, T=1 state. The (d, 2 He) probe appears as a
powerful spectroscopic tool for studying charge-exchange reactions in the
β + direction. The key issue here will be the high resolution of order 100
keV, which provides new and sometimes unexpected insight into nuclear
structure phenomena. This program has been launched at the AGOR
Superconducting Cyclotron Facility at the KVI Groningen. By now it
covers a wide field of physics questions ranging from few-body physics
(measurement of the neutron-neutron scattering length ann), the structure
of halo-nuclei ( 6 He, 7 He), to questions pertaining to the dynamics
of supernova explosions and nuclear synthesis (i.e. GT + distribution in
pf-shell nuclei), and more recently to the measurements of double-beta
decay matrix elements and the determination of half-lives of double-beta
decaying nuclei (e.g. 48 Ca, 116 Cd).
Plenary Talk HK 22.2 Wed 09:00 P
New results from BaBar — •Matthias Steinke for the BaBar
collaboration — Institut für Experimentalphysik I, Ruhr-Universität
Bochum, Germany
The BaBar experiment at the asymmetric high luminosity e + -e − collider
PEP II located at the Stanford Linear Accelerator Center has
recorded about 150 fb −1 of data since November 1999 at the Υ(4S) resonance
(10.58 GeV). Main goal of the experiment is the investigation of
the CP violation in B systems, which could be confirmed experimentally,
and the precise determination of parameters of the CKM matrix.
Beside this BaBar offers excellent experimental conditions for investigations
in many more fields, especially in meson spectroscopy. Here the
search for exotic states is a main topic.
Recent results from BaBar with emphasis on new charmed meson
states will be presented.