摘要
Proton-halo breakup behavior in theε0→0 limit(whereε0 is the ground-state binding energy)is stud-ied around the Coulomb barrier in the^(8)B+^(58)Ni reaction for the first time.For practical purposes,apart from the ex-perimental 8B binding energy of 137 keV,three more arbitrarily chosen values(1,0.1,0.01 keV)are considered.It is first shown that the Coulomb barrier between the core and the proton prevents the^(7)Be+p system from reaching the state of an open proton-halo system,w hich,among other factors,would require the ground-state wave function to extend to infinity in the asymptotic region,asε0→0.The elastic scattering cross section,which depends on the density of the ground-state wave function,is found to have a negligible dependence on the binding energy in this limit.The total,Coulomb and nuclear breakup cross sections are all reported to increase significantly fromε0=137 to 1.0 keV,and converge to their maximum values asε0→0.This increase is mainly understood as coming from a longer tail of the ground-state wave function forε0≤1.0 keV,compared to that forε0=137 keV.It is also found that the effect of the continuum-continuum couplings is to slightly delay the convergence of the breakup cross section.The analysis of the reaction cross section indicates a convergence of all the breakup observables asε0→0.These results provide a better sense of the dependence of the breakup process on the breakup threshold.
