Charged pion spectra measured in
58Ni
58Ni collisions at 1.06, 1.45 and 1.93 AGeV are interpreted in terms of a thermal model including the decay of Δ resonances. The transverse momentum spectra of ...pions are well reproduced by adding the pions originating from the Δ -resonance decay to the component of thermal pions, deduced from the high transverse momentum part of the pion spectra. About 10 and 18% of the nucleons are excited to Δ states at freeze-out for beam energies of 1 and 2 AGeV, respectively.
We present new experimental results concerning the azimuthal distributions of proton-likes, light and intermediate mass fragments at midrapidity for Au(100–800
A MeV) +Au collisions measured with the ...FOPI phase-I detector at GSI in Darmstadt. The azimuthal distributions are investigated as a function of the collision centrality, the incident energy, the fragment charge and transverse momentum. The azimuthal anisotropy is maximum for impact parameters around 7 fm. Intermediate mass fragments present a stronger out-of-plane emission signal than light fragments and a saturation is reached for
Z ⩾ 4. The azimuthal anisotropy increases with the fragment transverse momentum and decreases as the incident energy increases. The azimuthal anisotropy of
Z = 2 particles investigated as a function of the scaled fragment transverse momentum follows an universal curve for bombarding energies between 250–800
A MeV. A signature for a transition from in-plane to out-of-plane emission is evidenced at the lowest beam energies.
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 (
m
t) spectra have been studied as a function of rapidity at a beam energy 1.93
AGeV. The
m
t 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.
Pedagogy. The notebook of nursing students Sieffert, E; Lacheray, I; Pras, P ...
Soins. Formation, pedagogie, encadrement : avec la participation du CEEIEC,
2000
34
Journal Article
Small-angle correlations of Proton pairs produced in central Ni+Ni collisions at a beam energy of 1.93 AGeV are investigated with the FOPI detector System at GSI Darmstadt. A well-defined emission ...source is selected by triggering on central events which comprise about 8% of the total cross section. Simultaneous comparison of longitudinal and transverse correlation functions with the predictions of the Koonin model allows to unravel the space-time ambiguity of the emission process. Taking into account the strong collactive expansion of the participant zone, which introduces a reduction of the extracted source radius of more than 30% r.m.s. radius and emission time parameters of Rrms = ( 4.2 ± 1.2) fm and trms = (11+7-5) fm/c are extracted, respectively. In contrast, the analysis of the angle-integrated correlation function gives an upper limit Rrms = (7.0 ± 1.4) fm of the source radius.
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