12,393 research outputs found
Improvements to model of projectile fragmentation
In a recent paper [Phys. Rev. C 044612 (2011)] we proposed a model for
calculating cross-sections of various reaction products which arise from
disintegration of projectile like fragment resulting from heavy ion collisions
at intermediate or higher energy. The model has three parts: (1) abrasion, (2)
disintegration of the hot abraded projectile like fragment (PLF) into nucleons
and primary composites using a model of equilibrium statistical mechanics and
(3) possible evaporation of hot primary composites. It was assumed that the PLF
resulting from abrasion has one temperature T. Data suggested that while just
one value of T seemed adequate for most cross-sections calculations, it failed
when dealing with very peripheral collisions. We have now introduced a variable
T=T(b) where b is the impact parameter of the collision. We argue there are
data which not only show that T must be a function of b but, in addition, also
point to an approximate value of T for a given b. We propose a very simple
formula: T(b)=D_0+D_1(A_s(b)/A_0) where A_s(b) is the mass of the abraded PLF
and A_0 is the mass of the projectile; D_0 and D_1 are constants. Using this
model we compute cross-sections for several collisions and compare with data.Comment: 27 pages, 16 figure
Model of multifragmentation, Equation of State and phase transition
We consider a soluble model of multifragmentation which is similar in spirit
to many models which have been used to fit intermediate energy heavy ion
collision data. We draw a p-V diagram for the model and compare with a p-V
diagram obtained from a mean-field theory. We investigate the question of
chemical instability in the multifragmentation model. Phase transitions in the
model are discussed.Comment: Revtex, 9 pages including 6 figures: some change in the text and Fig.
Incorporating Radial Flow in the Lattice Gas Model for Nuclear Disassembly
We consider extensions of the lattice gas model to incorporate radial flow.
Experimental data are used to set the magnitude of radial flow. This flow is
then included in the Lattice Gas Model in a microcanonical formalism. For
magnitudes of flow seen in experiments, the main effect of the flow on
observables is a shift along the axis.Comment: Version accepted for publication in Phys. Rev. C, Rapid Communicatio
Nuclear multifragmentation within the framework of different statistical ensembles
The sensitivity of the Statistical Multifragmentation Model to the underlying
statistical assumptions is investigated. We concentrate on its micro-canonical,
canonical, and isobaric formulations. As far as average values are concerned,
our results reveal that all the ensembles make very similar predictions, as
long as the relevant macroscopic variables (such as temperature, excitation
energy and breakup volume) are the same in all statistical ensembles. It also
turns out that the multiplicity dependence of the breakup volume in the
micro-canonical version of the model mimics a system at (approximately)
constant pressure, at least in the plateau region of the caloric curve.
However, in contrast to average values, our results suggest that the
distributions of physical observables are quite sensitive to the statistical
assumptions. This finding may help deciding which hypothesis corresponds to the
best picture for the freeze-out stageComment: 20 pages, 7 figure
A study of the phase transition in the usual statistical model for nuclear multifragmentation
We use a simplified model which is based on the same physics as inherent in
most statistical models for nuclear multifragmentation. The simplified model
allows exact calculations for thermodynamic properties of systems of large
number of particles. This enables us to study a phase transition in the model.
A first order phase transition can be tracked down. There are significant
differences between this phase transition and some other well-known cases
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