On the isospin effects in flow and its disappearance and other related phenomena, S. Gautam, Department of Physics, Panjab University, Chandigarh, India − Nuclear reactions induced by radioactive ion beams provide a unique opportunity to extract useful information about the equation of state (EOS) of hot and dense asymmetric nuclear matter.  After intensive efforts in both theoretical and experimental front, EOS of symmetric nuclear matter is now well determined.  The collective transverse in-plane flow has found to be a useful tool for extracting the EOS.  The collective flow has been found to depend on isospin degree of freedom [1].  We aim to study the isospin effects in collective flow and in its disappearance at a particular energy called energy of vanishing flow (EVF) of isobaric pairs throughout the mass range and from central to peripheral collisions [2].  We also shed light on the relative importance of Coulomb potential, symmetry energy and nucleon-nucleon (nn) cross section in isospin effects.  We find the dominance of Coulomb potential in isobaric pairs. We also study the sensitivity of transverse flow to the symmetry energy and its density dependence in Fermi energy region as well as at high energies [3].  We find that flow is sensitive to symmetry energy and its density dependence in Fermi energy region whereas shows insensitivity at high energies because of the dominance of nn scattering than mean field.  As a next step, we study the isospin effects in EVF for isotopic pairs throughout the mass range.  Our study reveals that N/Z dependence of EVF is sensitive to symmetry energy and its density dependence and is almost insensitive to the isospin dependence of nn cross section, thus indicating that N/Z dependence of EVF can act as a probe to constrain symmetry energy at densities about twice the normal matter density. The study also points that lighter systems can act as better probes as compared to heavier ones.  In addition to this, we also study nuclear dynamics at EVF for systems having different neutron content.  We find that participant-spectator matter, density and anisotropy ratio shows nearly mass independent behavior for all the systems having different neutron content [4].

 

[1] B. A. Li et al., Phys. Rev. Lett. 76, 4492 (1996) ;  R. Pak et al., ibid. 78, 1022 (1997).

[2] S. Gautam et al., Phys. Rev. C 84, 014604 (2010), S. Gautam et al., Phys. Rev. C 83, 014603 (2011).

[3] S. Gautam et al., Phys. Rev. C 83, 034606 (2011).

[4] S. Gautam, Phys. Rev. C 83, 064604  (2011).