Weakly bound halo breakup of neutron- Li 7 and nucleon- Be 7 on a lead target

A comparative analysis of the breakup cross-sections, using continuum discretized coupled-channel approach, is presented for the weakly bound $p\text{\ensuremath{-}}$wave neutron-$^{7}\mathrm{Li}$ and nucleon-$^{7}\mathrm{Be}$ projectiles on the $^{208}\mathrm{Pb}$ target, by investigating the role of interaction effects between the core $(^{7}\mathrm{Li},$ $^{7}\mathrm{Be})$ with the target. The extra charge in the $^{8}\mathrm{B}$ has the effect to increase the Coulomb contribution in the breakup reaction channel. By fixing both projectile ground-state binding energies at 0.137 MeV ($^{8}\mathrm{B}$ experimental one), with incident energies at the Coulomb barrier and above, we found that the charge difference accounts for over 30% of the neutron$\text{\ensuremath{-}}^{7}\mathrm{Be}$ breakup cross sections, substantially larger than the corresponding one for proton$\text{\ensuremath{-}}^{7}\mathrm{Be}$. The large enhancement of the neutron-halo breakup cross-section with respect to the proton-halo case shown in this work is associated to dynamical effects coming from the excitation of the projectile internal continuum due to the nucleon-target and core-target interactions, together with the widely accepted static effects coming from the long wave-function tail of the weakly bound neutron. The interplay between these dynamical and static effects in the energy spectrum of the $^{8}\mathrm{B}$ fragments is visible, revealed by the peak of the energy distribution pushed to higher relative energies. This follows from the two-body final state interactions between the charged fragments distorted by the three-body reaction environment.