91 research outputs found
Spectator matter fragmentation in Au+Au reactions: Phase space analysis
Clusterization in phase space has been analyzed for peripheral Au+Au
reactions at 1000 AMeV using simulated annealing clusterization algorithm
(SACA). We investigate how these fragments are correlated in phase space and
compare our model calculations with minimum spanning tree (MST) method. Our
theoretical study highlights the importance of binding energy criterion in
recognizing the fragment structure. MST method however, fails to break-up the
spectator matter effectively and thus under-estimates the multiplicity of
intermediate mass fragments (IMFs).Comment: 2 pages, 2 figure
Momentum Dependence of Nuclear Mean Field and multifragmentation in Heavy-Ion Collisions
We report the consequences of implementing momentum dependent interactions
(MDI) on multifragmentation in heavy-ion reactions over entire collision
geometry. The evolution of a single cold nucleus using static soft equation of
state and soft momentum dependent equation of state demonstrates that inclusion
of momentum dependence increases the emission of free nucleons. However, no
heavier fragments are emitted artificially. The calculations performed within
the framework of quantum molecular dynamics approach suggest that MDI strongly
influence the system size dependence of fragment production. A comparison with
ALADiN experimental data justifies the use of momentum dependent interactions
in heavy-ion collisions
Microscopic approach to the spectator matter fragmentation from 400 to 1000 AMeV
A study of multifragmentation of gold nuclei is reported at incident energies
of 400, 600 and 1000 MeV/nucleon using microscopic theory. The present
calculations are done within the framework of quantum molecular dynamics (QMD)
model. The clusterization is performed with advanced sophisticated algorithm
namely \emph{simulated annealing clusterization algorithm} (SACA) along with
conventional spatial correlation method. A quantitative comparison of mean
multiplicity of intermediate mass fragments with experimental findings of
ALADiN group gives excellent agreement showing the ability of SACA method to
reproduce the fragment yields. It also emphasizes the importance of clustering
criterion in describing the fragmentation process within semi-classical model
Mass independence and asymmetry of the reaction: Multi-fragmentation as an example
We present our recent results on the fragmentation by varying the mass
asymmetry of the reaction between 0.2 and 0.7 at an incident energy of 250
MeV/nucleon. For the present study, the total mass of the system is kept
constant (ATOT = 152) and mass asymmetry of the reaction is defined by the
asymmetry parameter (? = | (AT - AP)/(AT + AP) |). The measured distributions
are shown as a function of the total charge of all projectile fragments,
Zbound. We see an interesting outcome for rise and fall in the production of
intermediate mass fragments (IMFs) for large asymmetric colliding nuclei. This
trend, however, is completely missing for large asymmetric nuclei. Therefore,
experiments are needed to verify this prediction
Study of fragmentation using clusterization algorithm with realistic binding energies
We here study fragmentation using \emph{simulated annealing clusterization
algorithm} (SACA) with binding energy at a microscopic level. In an earlier
version, a constant binding energy (4 MeV/nucleon) was used. We improve this
binding energy criterion by calculating the binding energy of different
clusters using modified Bethe-Weizs\"{a}cker mass (BWM) formula. We also
compare our calculations with experimental data of ALADiN group. Nearly no
effect is visible of this modification
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
Entropy and light cluster production in heavy-ion collisions at intermediate energies
The entropy production in medium energy heavy-ion collisions is analyzed in
terms of ratio of deuteronlike to protonlike clusters ()
using \emph{quantum molecular dynamics} (QMD) model. The yield ratios of
deuteronlike-to-protonlike clusters calculated as a function of participant
proton multiplicity closely agree with experimental trends. Our model
predictions indicate that full thermodynamical equilibrium may not be there
even for the central geometry. The apparent entropy extracted from the yield
ratios of deuteronlike-to-protonlike clusters, however, reflects the
universality characteristics \emph{i.e.} it is governed by the volume of
reaction independent of the target-projectile combination. Our calculations for
apparent entropy produced in central collisions of Ca+Ca and Nb+Nb at different
bombarding energies are in good agreement with Plastic Ball data.Comment: 13 pages, 6 figures, in pres
A comparative study of model ingredients: fragmentation in heavy-ion collisions using quantum molecular dynamics model
We aim to understand the role of NN cross-sections, equation of state as well
as different model ingredients such as width of Gaussian, clusterisation range
and different clusterisation algorithms in multifragmentation using quantum
molecular dynamics model. We notice that all model ingredients have sizable
effect on the fragment pattern.Comment: 12 Pages, 4 Figure
On the nuclear stopping in asymmetric colliding nuclei
Using an isospin-dependent quantum molecular dynamics (IQMD) model, nuclear
stopping is analyzed in asymmetric colliding channels by keeping the total mass
fixed. The calculations have been carried by varying the asymmetry of the
colliding pairs with different neutron-proton ratios in center of mass energy
250 MeV/nucleon and by switching off the effect of Coulomb interactions. We
find sizable effect of asymmetry of colliding pairs on the stopping and
therefore on the equilibrium reached in a reaction
- …