22 research outputs found
Neutron recognition in the LAND detector for large neutron multiplicity
The performance of the LAND neutron detector is studied. Using an
event-mixing technique based on one-neutron data obtained in the S107
experiment at the GSI laboratory, we test the efficiency of various analytic
tools used to determine the multiplicity and kinematic properties of detected
neutrons. A new algorithm developed recently for recognizing neutron showers
from spectator decays in the ALADIN experiment S254 is described in detail. Its
performance is assessed in comparison with other methods. The properties of the
observed neutron events are used to estimate the detection efficiency of LAND
in this experiment.Comment: 16 pages, 8 figure
The ASY-EOS experiment at GSI: investigating the symmetry energy at supra-saturation densities
The elliptic-flow ratio of neutrons with respect to protons in reactions of
neutron rich heavy-ions systems at intermediate energies has been proposed as
an observable sensitive to the strength of the symmetry term in the nuclear
Equation Of State (EOS) at supra-saturation densities. The recent results
obtained from the existing FOPI/LAND data for Au+Au collisions
at 400 MeV/nucleon in comparison with the UrQMD model allowed a first estimate
of the symmetry term of the EOS but suffer from a considerable statistical
uncertainty. In order to obtain an improved data set for Au+Au collisions and
to extend the study to other systems, a new experiment was carried out at the
GSI laboratory by the ASY-EOS collaboration in May 2011.Comment: Talk given by P. Russotto at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Charged-particle flow measured with the KRATTA detector in the ASY-EOS experiment
The flow of light charged particles from the Au+Au reaction at 400 AMeV measured with the KRATTA detector is presented. The results are compared with the FOPI data
Results of the ASY-EOS experiment at GSI: The symmetry energy at suprasaturation density
Directed and elliptic flows of neutrons and light charged particles were measured for the reaction 197Au+197Au at 400 MeV/nucleon incident energy within the ASY-EOS experimental campaign at the GSI laboratory. The detection system consisted of the Large Area Neutron Detector LAND, combined with parts of the CHIMERA multidetector, of the ALADIN Time-of-flight Wall, and of the Washington-University Microball detector. The latter three arrays were used for the event characterization and reaction-plane reconstruction. In addition, an array of triple telescopes, KRATTA was used for complementary measurements of the isotopic composition and flows of light charged particles. From the comparison of the elliptic flow ratio of neutrons with respect to charged particles with UrQMD predictions, a value γ = 0.72 ± 0.19 is obtained for the power-law coefficient describing the density dependence of the potential part in the parametrization of the symmetry energy. It represents a new and more stringent constraint for the regime of suprasaturation density and confirms, with a considerably smaller uncertainty, the moderately soft to linear density dependence deduced from the earlier FOPI-LAND data. The densities probed are shown to reach beyond twice saturation
KRATTA, a versatile triple telescope array for charged reaction products
A new detection system KRATTA, Krak\'ow Triple Telescope Array, is presented.
This versatile, low threshold, broad energy range system has been built to
measure the energy, emission angle, and isotopic composition of light charged
reaction products. It consists of 38 independent modules which can be arranged
in an arbitrary configuration. A single module, covering actively about 4.5 msr
of the solid angle at the optimal distance of 40 cm from the target, consists
of three identical, 0.500 mm thick, large area photodiodes, used also for
direct detection, and of two CsI(1500 ppm Tl) crystals of 2.5 and 12.5 cm
length, respectively. All the signals are digitally processed. The lower
identification threshold, due to the thickness of the first photodiode, has
been reduced to about 2.5 MeV for protons (~0.065 mm of Si equivalent) by
applying a pulse shape analysis. The pulse shape analysis allowed also to
decompose the complex signals from the middle photodiode into their ionization
and scintillation components and to obtain a satisfactory isotopic resolution
with a single readout channel. The upper energy limit for protons is about 260
MeV. The whole setup is easily portable. It performed very well during the
ASY-EOS experiment, conducted in May 2011 at GSI. The structure and performance
of the array are described using the results of Au+Au collisions at 400
MeV/nucleon obtained in this experiment.Comment: 10 pages, 18 figures, accepted by Nucl. Instr. and Meth.
Background reduction in long CsI(Tl) crystals
A simple method to reduce the background from secondary reactions in telescopes composed of long CsI(Tl) crystals is presented. The method has been developed for the KRATTA [1] modules
The ASY-EOS experiment at GSI: Investigating symmetry energy at supra-saturation densities
The elliptic-flow ratio of neutrons with respect to protons in reactions of neutron rich heavy-ions systems at intermediate energies has been proposed as an observable sensitive to the strength of the symmetry term in the nuclear Equation Of State (EOS) at supra-saturation densities. The recent results obtained from the existing FOPI/LAND data for 197Au+197Au collisions at 400 MeV/nucleon in comparison with the UrQMD model allowed a first estimate of the symmetry term of the EOS but suffer from a considerable statistical uncertainty. In order to obtain an improved data set for Au+Au collisions and to extend the study to other systems, a new experiment was carried out at the GSI laboratory by the ASY-EOS collaboration in May 2011