Effect of system size asymmetry on elliptical flow of different fragments in
heavy-ion collisions.
Varinderjit Kaur1 , Suneel Kumar1 and Rajeev K. Puri2
1
School of Physics and Material Science, Thapar University, Patiala-147004.
2
Department of Physics, Panjab University, Chandigarh-160014
Heavy-Ion Collisions at intermediate energies are the center of interest in present day
nuclear research. It allows searching for a large number of observables which may be
used as indicators of the properties of nuclear matter under extreme conditions.
Frequently these observables are related to the quantitative description of collective
effects such as the bounce-off of cold spectator matter in the reaction plane [1] and the
squeeze out of hot and compressed participant matter perpendicular to the reaction plane
[2]. Anisotropic collective flow [3], particularly elliptical flow, is a powerful probe to
understand the dynamics of heavy-ion collisions. A theoretical investigation of the flow
analysis for three different set of reactions of 8O16 + 54Xe136, 14Si28 + 54Xe124, 14Si28 +
124
40
112
has been studied. We have used different isotopes of Xe and Sn
50Sn , 20Ca + 50Sn
in such a way that the total number of nucleons remains the same in each set, i.e. 152.
The simulations have been carried out at different beam energies from 50 MeV/nucleon
to 250MeV/nucleon for an impact parameter b = 0.3 within the framework of Isospin
Quantum Molecular Dynamics (IQMD) model [4]. The isospin is treated explicitly (in
the so-called IQMD version) by including Coulomb potential, symmetry potential and nn
cross-section.
Our results show that as we move from asymmetry towards the
symmetry of the colliding partners, elliptical flow decreases. The effect of symmetry
energy can be seen in the fragment production and their elliptical flow. With increase in
beam energy, the isotropic distribution of free nucleons/LMF’s is clearly visible. The
stopping parameter Qzz and R also show change with change of symmetry of colliding
partners. As the cross-section for nn, np and pp is different therefore, the results are
expected to show change for the study carried out with different nn cross-sections.
Acknowledgement :
This work has been supported by the grant from Department of Science and Technology
(DST) Government of India vide Grant No.SR/WOS-A/PS-10/2008.
References:
[1] H. Stocker and W. Greiner, Phys. Rev. Lett.44, 725(1980).
[2] M.B.Tsang et.al., Phys. RevC53, 1959(1996); ibid Phys. Rev. Lett.102,
122701(2009)
[3] Yan Ting-Zhi, et.al., Chinese Phys.16, 2676-2682(2007).
[4] C. Hartnack Ph.D. thesis, GSI-Report(1993).
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