The trigger system of the ALICE dimuon arm is based on Resistive Plate Chambers (RPC). Besides a short description of the trigger system, the test results of a RPC proto-type with electrodes made of ...low resistivity bakelite (⋍ 3 · 10
9 Ω·cm) are presented. Rate capability, time resolution and cluster size have been measured for the RPC operated both in streamer and in avalanche mode. Although the rate capability is obviously higher in avalanche mode (few kHz/cm
2), remarkable results have been achieved even in streamer mode (several hundreds of Hz/cm
2).
Le spectromètre à muons du détecteur ALICE, installé au LHC, est dédié à la mesure des quarkonia (J/psi et upsilon) et des saveurs lourdes ouvertes qui se désintègrent en muons. Un grand nombre ...d'étapes (R&D, simulation et construction) ont été nécessaires pour réaliser les systèmes de tracking et de trigger du spectromètre. Les prises de données sont actuellement en cours. Ce document présente mes activités de recherche durant l'évolution du projet.
Using the FOPI detector at GSI Darmstadt, excitation functions of collective flow components were measured for the Au+Au system, in the reaction plane and out of this plane, at seven incident ...energies ranging from 100
A MeV to 800
A MeV. The threshold energies, corresponding to the onset of sideward-flow (balance energy) and squeeze-out effect (transition energy), are extracted from extrapolations of these excitation functions toward lower beam energies for charged products with
Z ⩾ 2. The transition energy is found to be larger than the balance energy. The impact parameter dependence of both balance and transition energies, when extrapolated to central collisions, suggests comparable although slightly higher values than the threshold energy for the radial flow. The relevant parameter seems to be the energy deposited into the system in order to overcome the attractive nuclear forces.
Test of the spatial resolution of MICROMEGAS detectors Cussonneau, J.P.; Labalme, M.; Lautridou, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/1998, Letnik:
419, Številka:
2-3
Journal Article
Recenzirano
A R&D program based on the MICROMEGAS 1detectors used as new possible LHC tracking chambers is poursuited at SUBATECH. Three prototypes have been constructed and tested in the 3GeV/c pion beam from ...the CERN PS. Results concerning the spatial resolutions as functions of gas mixtures, high voltages and the angular incidences of the particles are presented.
The mass distributions of baryon resonances populated in near-central collisions of Au on Au and Ni on Ni are deduced by defolding the $p_t$ spectra of charged pions by a method which does not depend ...on a specific resonance shape. In addition the mass distributions of resonances are obtained from the invariant masses of $(p, \pi^{\pm})$ pairs. With both methods the deduced mass distributions are shifted by an average value of -60 MeV/c$^2$ relative to the mass distribution of the free $\Delta(1232)$ resonance, the distributions descent almost exponentially towards mass values of 2000 MeV/c^2. The observed differences between $(p, \pi^-)$ and $(p, \pi^+)$ pairs indicate a contribution of isospin $I = 1/2$ resonances. The attempt to consistently describe the deduced mass distributions and the reconstructed kinetic energy spectra of the resonances leads to new insights about the freeze out conditions, i.e. to rather low temperatures and large expansion velocities.
Light-particle emission from Au+Au collisions has been studied in the bombarding-energy range 100–250
A·MeV, using
ΔE−
E
R telescopes in coincidence with the FOPI detector in its
phase I ...configuration. Center-of-mass energy spectra have been measured for
Z = 1,2 isotopes emitted in central collisions at CM polar angles between 60° and 90°. Evidence for a collective expansion is reported, on the basis of the mean kinetic energies of hydrogen isotopes. Comparison is presented with statistical calculations (WIX code). For CM kinetic energy spectra, fair agreement is found between data and a recently developed transport model.
We present new experimental data obtained with the FOPI detector at SIS, for the Au + Au heavy-ion collisions at 400
A MeV incident energy. The sideward flow, determined from a method without ...reaction-plane reconstruction, and the nuclear stopping are studied as a function of the centrality of the collisions. In order to study the nuclear in-medium effects, which act on the NN cross sections and potential and hence on experimental observables like the nuclear-matter flow and stopping, these results are compared with the predictions of two different QMD versions. The first one offers a fully microscopic calculation of the cross sections and potential in the G-matrix formalism and naturally includes the in-medium effects (this version is for the first time confronted with experiment). The second one uses a standard Skyrme potential plus a momentum-dependent term in order to mimic the in-medium effects.
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