72 research outputs found
Collective flow in heavy ion collisions at intermediate energies
We present results of a flow analysis for the set of reactions of 124,129Xe
projectiles and 112,124Sn targets at incident energies 100 and 150 A MeV
studied with the INDRA detector at GSI. The dependence on centrality and on p_t
of the directed and elliptic flow are determined for isotopically selected
reaction products with Z \le 3. The flow parameters v_1 and v_2, in general,
follow expected trends but isotopic effects are small.Comment: 3 pages, 2 figures, contributed talk at INPC, Tokyo, June 3-8, 2007,
to appear in the proceeding
Flow probe of symmetry energy in relativistic heavy-ion reactions
Flow observables in heavy-ion reactions at incident energies up to about 1
GeV per nucleon have been shown to be very useful for investigating the
reaction dynamics and for determining the parameters of reaction models based
on transport theory. In particular, the elliptic flow in collisions of
neutron-rich heavy-ion systems emerges as an observable sensitive to the
strength of the symmetry energy at supra-saturation densities. The comparison
of ratios or differences of neutron and proton flows or neutron and hydrogen
flows with predictions of transport models favors an approximately linear
density dependence, consistent with ab-initio nuclear-matter theories.
Extensive parameter searches have shown that the model dependence is comparable
to the uncertainties of existing experimental data. Comprehensive new flow data
of high accuracy, partly also through providing stronger constraints on model
parameters, can thus be expected to improve our knowledge of the equation of
state of asymmetric nuclear matter.Comment: 20 pages, 24 figures, review to appear in EPJA special volume on
nuclear symmetry energ
Isospin effects on the energy of vanishing flow in heavy-ion collisions
Using the isospin-dependent quantum molecular dynamics model we study the
isospin effects on the disappearance of flow for the reactions of +
and + as a function of impact parameter. We found
good agreement between our calculations and experimentally measured energy of
vanishing flow at all colliding geometries. Our calculations reproduce the
experimental data within 5%(10%) at central (peripheral) geometries
Bimodality - a general feature of heavy ion reactions
Recently, is has been observed that events with the {\it same} total
transverse energy of light charged particles (LCP) in the quasi target region,
, show two quite distinct reaction scenarios in the
projectile domain: multifragmentation and residue production. This phenomenon
has been dubbed "bimodality". Using Quantum Molecular Dynamics calculations we
demonstrate that this observation is very general. It appears in collisions of
all symmetric systems larger than Ca and at beam energies between 50 A.MeV and
600 A.MeV and is due to large fluctuations of the impact parameter for a given
. Investigating in detail the bin in
which both scenarios are present, we find that neither the average fragment
momenta nor the average transverse and longitudinal energies of fragments show
the behavior expected from a system in statistical equilibrium, in experiment
as well as in QMD simulations. On the contrary, the experimental as well as the
theoretical results point towards a fast process. This observation questions
the conjecture that the observed bimodality is due to the coexistence of 2
phases at a given temperature in finite systems.Comment: accepted PR
Coincidence measurement of residues and light particles in the reaction 56Fe+p at 1 GeV per nucleon with SPALADIN
The spallation of Fe in collisions with hydrogen at 1 A GeV has been
studied in inverse kinematics with the large-aperture setup SPALADIN at GSI.
Coincidences of residues with low-center-of-mass kinetic energy light particles
and fragments have been measured allowing the decomposition of the total
reaction cross-section into the different possible de-excitation channels.
Detailed information on the evolution of these de-excitation channels with
excitation energy has also been obtained. The comparison of the data with
predictions of several de-excitation models coupled to the INCL4 intra-nuclear
cascade model shows that only GEMINI can reasonably account for the bulk of
collected results, indicating that in a light system with no compression and
little angular momentum, multifragmentation might not be necessary to explain
the data.Comment: 4 pages, 5 figures, revised version accepted in Phys. Rev. Let
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