Isospin transport in heavy ion collisions at intermediate energies: new insights into the dynamical fission process

Caterina Ciampi (GANIL, France)

In the framework of heavy ion collisions, isospin transport phenomena can be used as a tool to gather information on the properties of nuclear matter far from equilibrium conditions [1]. The interest in this topic is manifold [2], due to its implications both in nuclear physics and in astrophysics [3].

In this seminar the most recent results from the INDRA-FAZIA apparatus will be presented, focusing on its first experiment, in which four reactions (^64,58Ni+^64,58Ni) at two beam energies (32 and 52 MeV/nucleon) are investigated. A clear signature of isospin diffusion is obtained by comparing the results of the two asymmetric systems with both the neutron rich and neutron deficient symmetric systems, exploiting the isospin transport ratio technique [4].

Special focus will be then given to the investigation of the dynamical fission (or breakup) of the quasiprojectile in semiperipheral and peripheral collisions, a fission process which has been linked to a dynamical origin, with short characteristic timescales [5]: quite recently, the study of the mechanisms of isospin drift and diffusion in this reaction channel has led to interesting results [6], whose interpretation, however, still presents some issues [7]. Here, we present an in-depth analysis of this output channel, aiming at the acquisition of a more comprehensive view of the phenomenon.
In the INDRA-FAZIA dataset, we find new evidence that, for the same reaction centrality, a higher degree of relaxation of the initial projectile-target isospin imbalance is achieved in the breakup channel with respect to the more populated binary output, possibly indicating the indirect selection of specific dynamical features. We exploit the information provided by AMD+GEMINI++ simulations of the studied systems [8,9] to propose an interpretation of our observation based on longer average projectile-target contact times related to the breakup channel: the model calculations support the hypothesis hereby presented.

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[2] B. A. Li et al., Phys. Lett. B 727, 276 (2013)
[3] K. Iida et al., Eur. Phys. J. A 50, 42 (2014)
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[6] A. Jedele et al., Phys. Rev. Lett. 118, 062501 (2017)
[7] S. Piantelli et al., Phys. Rev. C 101, 034613 (2020)
[8] A. Ono et al., Phys. Rev. Lett. 68, 2898 (1992)
[9] R. J. Charity et al., Phys. Rev. C 82, 014610 (2010)