G. Guillaume

Central collisions of Au on Au at 150, 250 and 400 A·MeV

Abstract Collisions of Au on Au at incident energies of 150, 250 and 400 A ·MeV were studied with the FOPI-facility at GSI Darmstadt. Nuclear charge ( Z ⩽ 15) and velocity of the products were detected with full azimuthal acceptance at laboratory angles 1° ⩽ θ lab ⩽ 30°. Isotope separated light charged particles were measured with movable multiple telescopes in an angular range of 6–90°. Central collisions representing about 1% of the reaction cross section were selected by requiring high total transverse energy, but vanishing side flow. The velocity space distributions and yields of the emitted fragments are reported. the data are analysed in terms of a thermal model including radial flow. A comparison with predictions of the quantum molecular model is presented.

A highly-segmented ΔE-time-of-flight wall as forward detector of the 4π-system for charged particles at the SIS/ESR accelerator

Abstract At the SIS/ESR accelerator facility at GSI in Darmstadt the 4π-detector system FOPI is under construction at present. It is designed for the investigation of central collisions of heavy ions in the energy range up to 2 A GeV. As phase I of this detector a forward wall has been built and used in various experiments. It comprizes a total number of 764 scintillators with an additional shell of 188 thin ΔE -detectors in front of it and covers the full azimuth of the polar angles from 1° to 30°. The velocity and the nuclear charge of the fragments are determined by a combined time-of-flight and ΔE measurement.

Study of n-γ discrimination with NE213 and BC501A liquid scintillators of different size

Abstract A comparative study of n-γ discrimination by the digital charge comparison method was carried out for NE213 and BC501A scintillators of different size coupled to a 130 mm diameter XP4512B photomultiplier. Particularly, the scintillators of diameter 50 mm × 50 mm size are compared with those of 4 l volume (160 mm in diameter and 200 mm in depth). The figure of merit, M , of 3.81 measured with the diameter 50 mm × 50 mm BC501A scintillator at 1 MeV energy lost by recoil electrons, is much better than M of 2.05 as observed with the 4 l volume cell. This is the effect of the reduced photoelectron yield by about 50% determined for the 4 l volume scintillator. Moreover, the slowing down of the light pulse and multiscattering of neutrons have a further influence on the lowering of the M factor. The study of the M factor versus the initial delay and width of the gate set at the slow component showed that the early light of the slow component represented often by the intermediate component with the decay time constant of about 30 ns is of great importance for the n-γ discrimination. Particularly, for the 4 l volume cells it is sufficient to limit the width of the gate at the slow component to about 300 ns. The comparison of the NE213 and BC501A scintillators showed that the BC501A scintillator exhibits a larger light yield evidently observed for the 4 l volume cell and thus giving a better n-γ discrimination.

On the transverse momentum distribution of strange hadrons produced in relativistic heavy ion collisions

Particles with strange quark content produced in the system 1.93A·GeV58Ni on58Ni have been investigated at GSI Darmstadt with the FOPI detector system. The correlation of these produced particles was analyzed with respect to the reaction plane.Λ baryons exhibit a very pronounced sideward flow pattern which is qualitatively similar to the proton flow. However, the kaon (K+,Ks0) flow patterns are significantly different from that of the protons, and their form may be useful to restrict theoretical models on the form of the kaon potential in the nuclear medium.

K+ production in the reaction 58Ni+58Ni at incident energies from 1 to 2 a GeV

Abstract Semi-inclusive triple differential multiplicity distributions of positively charged kaons have been measured over a wide range in rapidity and transverse mass for central collisions of 58Ni with 58Ni nuclei. The transverse mass (mt) spectra have been studied as a function of rapidity at a beam energy 1.93 AGeV. The mt distributions of K+ mesons are well described by a single Boltzmann-type function. The spectral slopes are similar to that of the protons indicating that rescattering plays a significant role in the propagation of the kaon. Multiplicity densities have been obtained as a function of rapidity by extrapolating the Boltzmann-type fits to the measured distributions over the remaining phase space. The total K+ meson yield has been determined at beam energies of 1.06, 1.45, and 1.93 A GeV, and is presented in comparison to existing data. The low total yield indicates that the K+ meson can not be explained within a hadro-chemical equilibrium scenario, therefore indicating that the yield does remain sensitive to effects related to its production processes such as the equation of state of nuclear matter and/or modifications to the K+ dispersion relation.Semi-inclusive triple differential multiplicity distributions of positively charged kaons have been measured over a wide range in rapidity and transverse mass for central collisions of

The light yield response of NE213 organic scintillators to charged particles resulting from neutron interactions

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Study of n-γ discrimination by digital charge comparison method for a large volume liquid scintillator

Ni with

Identification of Different Reaction Channels of High-energy Neutrons in Liquid Scintillators By the Pulse-shape Discrimination Method

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Comparative study of new 130 mm diameter fast photomultipliers for neutron detectors

Ni nuclei. The transverse mass (

Study of the 40Ar + 68Zn reaction at 27.6 MeVNucleon

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