Monday, March 11, 2002 - DPG-Tagungen

Nuclear Physics Tuesday
tions of the proposed detector system. Particular emphasis will be placed
on the performance of the central tracking detectors which is a crucial
factor for the feasibility of these extentions to the antiproton physics
program.
[1] Conceptual Design Report: http://www.gsi.de/GSI-Future
HK 12.6 Tue 10:30 Foyer Chemie
The Search for Excited Glue with Antiproton Beams — •C.
Schwarz for the Antiproton Physics Study Group collaboration — GSI,
Darmstadt
One of the main thrusts of the recently proposed High Energy Storage
Ring (HESR) for antiprotons at GSI [1] is the search for gluonic excitations
in the charmonium mass range. Beams of cooled antiprotons with
momenta of 1.5 to 15 GeV/c on an internal target allow the search for
charmed hybrids and glueballs up to a mass of 5.5 GeV/c 2 . Here, all
states are directly populated and allow a measurement with a mass resolution
of δm/m ≈ 10 − 5. In the charmed region the number of resonances
is relatively small and the relative decay widths are narrower than in the
light quark sector. Hence, unambigous identification of the production
and formation experiments is easily performed. The proposed detector
is capable to measure electrons, gammas, and the hadronic final states.
Above points and implicated good particle identification based on imaging
Cherenkov detectors (DIRC,Aerogel Counters) is emphasized in the
present poster This concept of particle identification has been proven to
work by GEANT4 simulations. The measurement of hadronic channels
will allow a selective filtering of final states with gluonic (bosonic) degrees
of freedom.
[1] Conceptual Design Report: http://www.gsi.de/GSI-Future
HK 12.7 Tue 10:30 Foyer Chemie
Hypernuclear Physics with Antiprotons — •J. Pochodzalla for
the Antiproton Physics Study Group collaboration — Inst. f. Kernphysik,
Mainz
One of the main components of the proposed international accelerator
facility at the GSI [1] is a storage ring that allows high luminosity
in-ring experiments with cooled antiprotons between 1.5 and 15 GeV/c.
Due to the large yield of hyperon-antihyperon pairs produced at these
energies a large-scale production of single and double hypernuclei under
unique experimental conditions will be feasible. The precision γ-ray
spectroscopy of these exotic nuclei and the study of their weak decays
provide a large variety of new and exciting perspectives ranging from genuine
hypernuclear states with new symmetries not available in ordinary
nuclei, over non-mesonic weak decays which offer the unique chance to
study the interplay of the quark-exchange and meson-exchange aspects of
the baryon-baryon forces, up to the possibility to study basic properties
of hyperons and strange exotic objects. The physics potential of these
measurements will be presented together with detailed considerations on
the technical realisation of this project.
[1] Conceptual Design Report: http://www.gsi.de/GSI-Future
HK 12.8 Tue 10:30 Foyer Chemie
Calibration of the neutron polarimeter for GE,n — •Frank Klein
— Institut für Kernphysik, J. Gutenberg-Universität Mainz
Previous double polarization measurements of GE,n at the Mainz
microtron MAMI yielded a new parametrization for the electric form
factor of the neutron [1]. This parametrization lies almost a factor of
two above the so far favoured extraction of GE,n from elastic D(e, e ′ )
scattering, where the Paris potential has been used [2]. In order to verify
GE,n in a model-independent way also at higher momentum transfers in
the range of 0.6 − 0.8 (GeV/c) 2 , a neutron polarimeter for a D(�e, e ′ �n)p
experiment was built at the three-spectrometer facility. The results
from the calibration of this polarimeter will be presented.
This work was supported by the DFG (SFB 443).
[1] C. Herberg et al., Eur. Phys. J. A5, 131 (1999)
[2] S. Platchkov et al., Nucl. Phys. A 510, 740 (1990)
HK 12.9 Tue 10:30 Foyer Chemie
Analysis of the pilot experiment (e,e ′ pn) at MAMI — •J. Heim
— Physikalisches Institut, Universität Tübingen, for the Amsterdam,
Glasgow, Mainz (A1) and Tübingen Collaboration
Two-nucleon emission experiments with real and virtual photons represent
an important tool for the study of nuclear many-body systems
beyond the independent particle motion. 3 He and 16 O have been selected
as the benchmark targets for a comprehensive investigations. The
(e,e ′ pp) and the (γ,pN) reactions studied so far have shown indications
of the role of nucleon-nucleon correlations competing with two-body currents
which also result in 2N emission. The (e,e ′ pn) reaction are expected
to give information on tensor correlations, which cannot be seen in pp
knockout. The analysis of the pilot experiment including D, 3 He and 16 O
targets will be presented.
This work is supported by DFG, DAAD, EPSRC, NWO and FOM.
HK 12.10 Tue 10:30 Foyer Chemie
First Analysis of COMPASS Data — •Martin von Hodenberg,
A. Danasino, H. Fischer, J. Franz, A. Grünemeier, S. Hedicke,
F.H. Heinsius, F. Karstens, W. Kastaun, K. Königsmann, J.
Reymann, T. Schmidt, H. Schmitt, andJ. Worch for the COM-
PASS collaboration — Fakultät für Physik, Universität Freiburg
COMPASS is an experiment at the SPS at CERN, which is aiming at a
better understanding of the spin structure of the nucleon, by performing
a measurement of the gluon polarisation ∆G/G. In order to achieve this
goal, polarised muons with an energy of 160 GeV are scattered from a
polarised LiD-target and events are studied where the underlying process
is the fusion of a virtual photon with a gluon of the nucleon. In the year
2001 COMPASS has taken its first data with an almost complete setup
and the analysis is in full activity. The presentation will inform about
the current status of the ongoing analysis.
This project is supported by BMBF.
HK 12.11 Tue 10:30 Foyer Chemie
Der Myontrigger des COMPASS Experiments — •Mario Leberig
für die COMPASS-Kollaboration — Institut für Kernphysik, Universität
Mainz
Eines der Ziele der COMPASS-Kollaboration ist die Messung des
Gluonbeitrags zum Nukleonspin in der polarisierten tiefinelastischen
Myon–Nukleon–Streuung. Dazu steht am SPS (CERN) ein polarisierter
160 GeV Myonstrahl mit einer Intensität von etwa 5 · 10 7 µ/s zur
Verfügung. Die besondere Kinematik des interessanten Prozesses – der
Photon-Gluon-Fusion – und die Eigenarten des Myonstrahles machen
den Aufbau eines vielschichtigen Triggersystems nötig. Der Vortrag beschreibt
das Triggerkonzept und dessen Realisierung für die Datennahmeperiode
im Sommer 2001. Ein besonderer Schwerpunkt wird dabei
auf die Bestimmung der Triggereigenschaften Anhand aktueller Daten
gelegt.
HK 12.12 Tue 10:30 Foyer Chemie
of the
New Results on the Polarized Structure Function gd 1
Deuteron from the HERMES Experiment — •Christoph
Weiskopf for the HERMEScollaboration — University of Erlangen,
Germany
The HERMESexperiment at DESY investigates the spin structure of
the nucleon in deep-inelastic scattering of longitudinally polarized electrons
or positrons on polarized internal gas targets of high purity. The
scattered and produced particles are detected in a forward spectrometer
with high momentum and angular resolution and a reliable particle
identification.
Between 1998 and 2000, data have been taken with a polarized atomic
deuterium target. The double-spin asymmetry Ad 1 in the virtual-photon
nucleon cross section has been measured, which is directly related to the
spin structure function gd 1 .
Compared to previous analyses of HERMESdeuteron data, the kinematic
range has been extended to values of Bjorken-x down to 0.0021 and
photon virtualities Q2 down to 0.1 GeV 2 . The data analysis is outlined
in its most important steps, and the most recent results are presented.
This work is supported by the German Bundesministerium für Bildung
und Forschung.
HK 12.13 Tue 10:30 Foyer Chemie
Azimuthal Single-Spin Asymmetries in Semi-Inklusive Deep-
Inelastic Scattering — •C. Schill for the HERMEScollaboration —
Fakultät für Physik der Universität Freiburg, Hermann-Herder-Str. 3,
D-79104 Freiburg.
In the HERMESexperiment azimuthal single-spin asymmetries have
been observed in semi-inclusive deep-inelastic scattering of 27.5 GeV electrons
off a polarized hydrogen target. Azimuthal target spin asymmetries
provide access to the chiral-odd spin structure function h1(x, Q 2 )
of the nucleon. This structure function is related to the transversity
distribution δq(x) of the quarks in the nucleon. The transversity distri-