We use a three-body Continuum Discretized Coupled Channel (CDCC) model to
investigate Coulomb and nuclear effects in breakup and reaction cross sections.
The breakup of the projectile is simulated by a finite number of square
integrable wave functions. First we show that the scattering matrices can be
split in a nuclear term, and in a Coulomb term. This decomposition is based on
the Lippmann-Schwinger equation, and requires the scattering wave functions. We
present two different methods to separate both effects. Then, we apply this
separation to breakup and reaction cross sections of 7Li + 208Pb. For breakup,
we investigate various aspects, such as the role of the alpha + t continuum,
the angular-momentum distribution, and the balance between Coulomb and nuclear
effects. We show that there is a large ambiguity in defining the 'Coulomb' and
'nuclear' breakup cross sections, since both techniques, although providing the
same total breakup cross sections, strongly differ for the individual
components. We suggest a third method which could be efficiently used to
address convergence problems at large angular momentum. For reaction cross
sections, interference effects are smaller, and the nuclear contribution is
dominant above the Coulomb barrier. We also draw attention on different
definitions of the reaction cross section which exist in the literature, and
which may induce small, but significant, differences in the numerical values.Comment: 12 pages, 11 figure
