359 research outputs found
Effect of mass asymmetry on the mass dependence of balance energy
We demonstrate the role of the mass asymmetry on the balance energy (Ebal) by
studying asymmetric reactions throughout the periodic table and over entire
colliding geometry. Our results, which are almost independent of the system
size and as well as of the colliding geometries indicate a sizeable effect of
the asymmetry of the reaction on the balance energy.Comment: Journal of Physics - Conference Series - Online end of March (2011
Pedestal and Peak Structure in Jet Correlation
We study the characteristics of correlation between particles in jets
produced in heavy-ion collisions. In the framework of parton recombination we
calculate the and distributions of a pion associated with a
trigger particle. The origin of the pedestal in is related to the
longitudinal expansion of the thermal partons that are enhanced by the energy
loss of hard partons traversing the bulk medium. The peaks in and
are related to the same angular spread of the shower partons in a
jet cone. No artificial short- or long-range correlations are put in by hand. A
large part of the correlation between hadrons in jets is due to the correlation
among the shower partons arising from momentum conservation. Recombination
between thermal and shower partons dominates the correlation characterisitics
in the intermediate region.Comment: 14 pages in LaTex and 2 figures in ep
Study of system- size effects in multi- fragmentation using Quantum Molecular Dynamics model
We report, for the first time, the dependence of the multiplicity of
different fragments on the system size employing a quantum molecular dynamics
model. This dependence is extracted from the simulations of symmetric
collisions of Ca+Ca, Ni+Ni, Nb+Nb, Xe+Xe, Er+Er, Au+Au and U+U at incident
energies between 50 A MeV and 1 A GeV. We find that the multiplicity of
different fragments scales with the size of the system which can be
parameterized by a simple power law.Comment: 7 pages, 3 figures, latex2e:elsart.cl
Angular hadron correlations probing the early medium evolution
Hard processes are a well calibrated probe to study heavy-ion collisions.
However, the information to be gained from the nuclear suppression factor R_AA
is limited, hene one has to study more differential observables to do medium
tomography. The angular correlations of hadrons associated with a hard trigger
appear suitable as they show a rich pattern when going from low p_T to high
p_T. Of prime interest is the fate of away side partons with an in-medium
pathlength O(several fm). At high p_T the correlations become dominated by the
punchtrough of the away side parton with subsequent fragmentation. We discuss
what information about the medium density can be gained from the data.Comment: Talk given at the 19th International Conference on Ultrarelativistic
Nucleus-Nucleus Collisions: Quark Matter 2006 (QM 2006), Shanghai, China,
14-20 Nov 200
Lambda(1520) production in d+Au collisions at RHIC
Recent results of (1520) resonance production in d+Au collisions at
200 GeV are presented and discussed in terms of the
evolution and freeze-out conditions of a hot and dense fireball medium. Yields
and spectra are compared to results from p+p and Au+Au collisions. The
(1520)/ ratio in d+Au collisions ratio is consistent with the
ratio in p+p collisions. This suggests a short time for elastic interactions
between chemical and thermal freeze-out. One can conclude that the interaction
volume in d+Au collisions is small.Comment: 4 Pages, 3 figures, conference proceedings Quark Matter 200
Influence of momentum-dependent interactions on balance energy and mass dependence
We aim to study the role of momentum-dependent interactions in transverse
flow as well as in its disappearance. For the present study, central collisions
involving mass between 24 and 394 are considered. We find that
momentum-dependent interactions have different impact in lighter colliding
nuclei compared to heavier colliding nuclei. In lighter nuclei, the
contribution of mean field towards the flow is smaller compared to heavier
nuclei where binary nucleon-nucleon collisions dominate the scene. The
inclusion of momentum-dependent interactions also explains the energy of
vanishing flow in reaction which was not possible with the
static equation of state. An excellent agreement of our theoretical attempt is
found for balance energy with experimental data throughout the periodic table
Disappearance of Transverse Flow in Central Collisions for Heavier Nuclei
For the first time, mass dependence of balance energy only for heavier
systems has been studied. Our results are in excellent agreement with the data
which allow us to predict the balance energy of U+U, for the first time, around
37-39 MeV/nucleon. Also our results indicate a hard equation of state along
with nucleon-nucleon cross-section around 40 mb.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Intermolecular Interactions and the Theory of Electron Transfer Between Hexaaquoiron Ions and Hexaammineruthenium Ions in Water.
Theoretical studies of the electron transfer rates between hexaaquoiron(II) and (III) ions, and between hexaammineruthenium(II) and (III) ions in aqueous solutions have been undertaken using detailed representations of the interaction potentials and including the flexibility of the ligand geometry. This is done through an intuitive and efficient computational scheme involving tested site-site potentials for water and ammonia. The calculations on the ferrous-ferric electron exchange indicate that fluctuations in the configuration of the hydration shell are important and affect the rate significantly. In the hexaammineruthenium reaction, there is no evidence for any substantial contribution from this factor, although rates tend to be consistently lower than experimental results. This may indicate a weakness in the ammonia-ammonia potential function used or in the treatment of the electronic coupling matrix element
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