The incident energy at which the azimuthal distributions in semicentral heavy-ion collisions change from in-plane to out-of-plane enhancement —
E
tran is studied as a function of mass of emitted ...particles, their transverse momentum and centrality for Au+Au collisions. The analysis is performed in a reference frame rotated with the sidewards flow angle (
Θ
flow) relative to the beam axis.
A systematic decrease of
E
tran as function of mass of the reaction products, their transverse momentum and collision centrality is evidenced.
The predictions of a microscopic transport model (IQMD) are compared with the experimental results.
Four different combinations of 9644Ru and 9640Zr nuclei, both as projectile and target, were investigated at the same bombarding energy of 400A MeV using a 4pi detector. The degree of isospin mixing ...between projectile and target nucleons is mapped across a large portion of the phase space using two different isospin-tracer observables, the number of measured protons and the tritium to 3He yield ratio. The experimental results show that the global equilibrium is not reached even in the most central collisions. Quantitative measures of stopping and mixing are extracted from the data. They are found to exhibit a quite strong sensitivity to the in-medium ( n,n) cross section used in microscopic transport calculations.
Experimental data on K
+ meson and proton sideward flow measured with the FOPI detector at SIS/GSI in the reactions Ru+Ru at 1.69
A GeV and Ni+Ni at 1.93
A GeV are presented. The K
+ sideward flow is ...found to be anti-correlated (correlated) with the one of protons at low (high) transverse momenta. When compared to the predictions of a transport model, the data favour the existence of an in-medium repulsive K
+-nucleon potential.
Directed sideward flow of light charged particles and intermediate mass fragments was measured in different symmetric reactions at bombarding energies from 90 to 800
A MeV. The flow parameter is ...found to increase with the charge of the detected fragment up to
Z = 3–4 and then turns into saturation for heavier fragments. Guided by simple simulations of an anisotropic expanding thermal source, we show that the value at saturation can provide a good estimate of the flow angle, Θ
flow, in the participant region. It is found that Θ
flow depends strongly on the impact parameter. The excitation function of Θ
folw reveals striking deviations from the ideal hydrodynamical scaling. The data exhibit a steep rise of Θ
flow to a maximum at around 250 – 400
A MeV, followed by a moderate decrease as the bombarding energy increases further.
New results on nuclear collective flow are presented for central and semi-central Ru + Ru collisions at 400
A MeV measured with the FOPI detector at GSI-Darmstadt. The source shape parameters, flow ...angle and aspect ratios, are extracted from Gaussian fits to in-plane and out-of-plane momentum distributions. The orientation and the shape of the source exhibit different trends according to the investigated phase space region. The shape parameters of the participant source are studied as a function of the particle mass and collision centrality. The flow angle is found to be independent of the particle mass. Both the flow angle and the aspect ratios depend sensitively on the impact parameter. Detailed comparisons with the predictions of the isospin quantum molecular dynamics model are performed. It is shown in particular that the source shape parameters permit to extract information on the in-medium nucleon–nucleon cross section.
A systematic study of the elliptic flow in Au+Au collisions at energies from 0.09 to 1.49 AGeV is presented. The experimental information allows us to extract information about the reaction dynamics ...and, by comparison with the IQMD transport model, the Equation of State (EoS) of nuclear matter.
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