Coulomb and Nuclear Breakup at Low Energies: Scaling Laws

Abstract

Abstract. We report on a recent work on the low-energy behavior of the breakup cross section in so far as it has important role in the fusion of weakly bound and halo nuclei at near-barrier energies. We assess the way the nuclear component of this cross section scales with the target mass. In complete accord with previous finding at higher energies we verify that the low energy behavior of the breakup cross section for a given projectile and relative center of mass energy with respect to the Coulomb barrier height scales as the cubic root of the mass number of the target. Surprisingly we find that the Coulomb component of the breakup cross section at these low energies also obeys scaling, but with a linear dependence on the target charge. Our findings are important when planning for experiments involving these exotic nuclei.The effect of the coupling to the breakup channel on the complete fusion of weakly bound, and especially, halo nuclei, has been under great scrutiny both experimentally and theoretically [1]. It seems that this coupling hinders the fusion at energies above the barrier, and enhances the tunneling-dominated fusion below the barrier [2]. Owing to the importance of the breakup channel at these low energies, we make an effort to understand its cross section, and the relative importance of its Coulomb and the nuclear components. In particular, we investigate the dependence of these components on the mass number of the target nucleus. To be more specific we mention that in analyzing data on elastic breakup, the cross section is written as the sum of the Coulomb breakup piece, plus the nuclear breakup piece, plus the interference term.The interest lies in σ bu C , as through it one can extract information about the collective response of halo and other weakly (bound) nuclei. What is first done (wrongly) is to ignore σ bu inter f erence , and consider σ bu N to scale linearly with the mass number of the target nucleus. We rely on a recent study of this topic, especially with regards to the dependence on the target mass, made at higher energies, [3,4]. According to this study, the nuclear breakup cross section behaves at a given value of the bombarding energy, E Lab as,a