Heavy-ion collisions offer the possibility to probe nuclear matter under different conditions of densities and temperatures. At high excitation energies the nuclei may break-up into many intermediate-mass fragments, the so called multifragmentation. In multifragmentation, nuclear matter at low densities and, more generally, modes of disintegration of dynamically unstable systems are probed. In particular, the expected link with the nuclear liquid-gas phase transition provides a continuing motivation for studying multifragmentation. In these reactions, systems of small and intermediate-mass nuclei surrounded by a nucleon gas may be produced, with properties close to what is expected in stellar processes as, e.g., supernova II explosions [1]. Experimental extraction of in-medium modifications of the properties of hot nuclei, in particular, their symmetry energy [2] will be important for understanding the production of nuclei and their interaction in stellar matter. Also properties of the high-density zones of the collision may be studied in the fragmentation of excited projectile spectators. The velocities of projectile residues are predicted to be sensitive to the non-local features of the nuclear mean field [3].

Isotopic effects originating from the two-fluid nature of nuclear matter [4], reflect the strength of the symmetry term in the equation of state whose density dependence is of importance for astrophysical applications. Experiments using the existing GSI facilities [5] have shown that secondary beams of exotic nuclei are useful and necessary for obtaining systems with a sufficiently broad range of isotopic composition. With the new facility, this can be further extended, in particular to neutron-rich asymmetric matter for which the effects of the symmetry term are most strongly pronounced.

Projectile fragmentation of secondary beams in conjunction with γ-ray spectroscopy is a powerful method to explore excited states in exotic nuclei. This method is also addressed in the LEB LoI. The R³B setup is particularly well suited for cases at the very limits of the production rates, i.e., for the most exotic nuclei. Here, the better transmission using high-energy beams and the high efficiency of the γ-calorimeter is advantageous.

[1] A.S. Botvina and I.N. Mishustin, Phys. Lett. B 584 (2004) 233.

[2] A. Le Fevre et al., Phys. Rev. Lett. 94 (2005) 162701.

[3] M.V. Ricciardi et al., Phys. Rev. Lett. 90 (2003) 212302

[4] H. Müller and B.D. Serot, Phys. Rev. C 52 (1995) 2072.

[5] K. Kezzar et al., (ALADIN-FRS-LAND collaborations), SIS experiment S254.