Monday, March 11, 2002 - DPG-Tagungen

Nuclear Physics Monday
strange hadrons Λ, ¯ ΛandK 0 s are identified by reconstructing their decay
topologies. The charged decay products as well as the charged Kaons
were measured with 4 Time Projection Chambers (TPCs), two of them
are located inside 2 large dipole magnets, the other two downstream of
the magnets symmetrically to the beam line. Transverse mass spectra
and rapidity distributions for Λ and charged Kaons will be shown for
all three energies. The multiplicities at mid-rapidity and the total yields
will be studied as a function of collision energy together with AGSand
RHIC measurements and compared with model predictions. The ratio
Λ/π as well as K + /π + shows a non-monotonic energy dependence and
has a maximum between top AGSand 40 A·GeV.
∗ Supported by BMBF und GSI.
Group Report HK 6.3 Mon 17:15 E
Recent Results from the WA98-Experiment — •Henner
Büsching for the WA98 collaboration — University of Münster,
Münster, Germany
Recent results from the WA98 experiment with p and Pb induced reactions
at 158 AGeV are presented. The CERN-SPS experiment WA98
investigates the properties of hot, dense matter with the main focus on
the measurement of photons and neutral mesons with the leadglass detector
LEDA.
Azimuthal γ-γ correlations at high pT which are influenced by jet-like
structures and elliptic flow have been studied. An influence of energy loss
effects (jet-quenching) should be evident in a characteristic modification
of the correlation. A clear indication of back-to-back correlations can be
seen with strong dependence on the pT of the photons and the size of the
system.
Results on transverse mass spectra of neutral pions measured at central
rapidity are presented for impact parameter selected Pb+Pb collisions.
In going from peripheral to medium central collisions there is a nuclear
enhancement increasing with transverse mass similar to the Cronin effect,
while for very central collisions this enhancement appears to be weaker
than expected.
Finally, results on event-by-event fluctuations of average transverse
momentum of photons are presented. The magnitude of those fluctuations
can indicate the equilibration level attained in the Pb+Pb collisions.
HK 6.4 Mon 17:45 E
Two particle correlations in STAR — •Dominik Flierl, Clemens
Adler, Jens Berger, Thomas Dietel, Sören Lange, Reinhard
Stock, andChristof Struck for the STAR collaboration — Universität
Frankfurt
The STAR detector system at RHIC is built to detect a large fraction
of the hadrons produced in collisions of ultra relativistic heavy ions. The
large TPC as the central detector of STAR identifies species and momentum
of emitted particles. Most of the detected particles are pions, but a
higher level trigger enables STAR also to search for rare particles. Those
probes carry information about the early stages of the collision, but the
expansion of highly compressed nuclear matter is best observed with the
most abundant species : pions. Collective flow and spatial conditions
at thermal freeze out when the pions leave the interaction volume are
accessible by two pion correlations. We will present results from charged
pion HBT studies at √ sNN = 130GeV.
Supported by BMBF and GSI.
HK 6.5 Mon 18:00 E
Directed and Elliptical Flow Measured with the Forward-TPCs
of the STAR Experiment — •Markus Oldenburg, Volker
Eckardt, Andreas Gärtner, Patrizia Krok, Gaspare Lo
Curto, Maria Mora, Jörn Putschke, Norbert Schmitz,
Andreas Schüttauf, Frank Simon, Janet Seyboth, Peter
Seyboth, and Michael Vidal — Max-Planck-Institut für Physik,
Föhringer Ring 6, 80805 München, Germany
The STAR detector at the Relativistic Heavy Ion Collider (RHIC) measures
the hadronic observables of Au+Au collisions at √ sNN = 200 GeV
per nucleon pair. The ’Max-Planck-Institut für Physik’ in Munich contributes
two Forward-TPCs which expand the overall acceptance of
STAR into the pseudorapidity region 2.5 < |η| < 4.
Hydrodynamical models predict that in peripheral heavy-ion collisions
the initial spatial anisotropy of the reaction zone is transformed into an
anisotropy in the momentum distribution of the produced particles. This
is caused by the pressure gradient generated at a very early stage of the
collision. Anisotropic flow measures these azimuthal anisotropies by a
Fourier expansion of the azimuthal angular distribution of the detected
hadrons.
Due to their acceptance coverage the FTPCs are suited to measure not
only elliptical flow v2 (2 nd order Fourier coefficient) as the TPC already
did in the region |η| < 1.5 but also directed flow v1 (1 st order Fourier
coefficient). Therefore these detectors allow the determination of the (up
to now) unknown sign of v2. In this talk a feasibility study and first
results of the flow measurement with the FTPCs will be presented.
HK 6.6 Mon 18:15 E
Measurement of the Transverse Energy Distribution at Midrapidity
in √ sNN = 130 GeV Au + Au Collisions by the PHENIX-
Experiment at RHIC — •Christian Klein-Bösing —University
of Münster, Germany
The Relativistic Heavy Ion Collider (RHIC) in Brookhaven/USA
started operation in the summer of 2000. During the first running period
of RHIC gold-gold collisions with energies up to √ sNN = 130 GeV has
been created. The PHENIX detector at RHIC is able to measure the
properties of nuclear matter at the highest temperatures and energy
densities produced in these collisions.
To allow an estimation of the energy density the measurement of energy
produced transverse to the beam direction provides valuable information,
which can be compared to predictions of a phase transition at
energy densities of about one GeV/fm 3 . The centrality dependence of
the transverse energy is compared to results at lower energies from other
experiments.
HK 6.7 Mon 18:30 E
Neutral Pion Spectra in Au+Au collisions at √ s NN = 130 GeV
— •Stefan Bathe for the PHENIX collaboration — University of
Münster, Germany
Transverse momentum spectra for neutral pions in the range 1 GeV/c