for each nucleon Why an optical model ? A 1 nucleons A 2 nucleons N=A1+A2 equations to solve.... N body problem one body problem a particle with a mass  is in a potential well V(r) which replaces all the interactions between the different nucleons.  :reduced mass of the system all the interactions between the nucleons are replaced by an average and central interaction V(r) between the projectile and the target Optical model References: P. E. Hodgson, The nucleon optical potential, Clarendon Press, 1994 G. R. Satchler, Direct nuclear reactions, Oxford University Press, New York, 1983

Optical potential V(r) = U(r) + i W(r) The optical model used to describe the interaction between two nuclei is inspired by the optical phenomena. represents the elastic scattering reflexion of the incident wave imaginary real partimaginary part absorption of the incident wave simulates the loss of flux due to no elastic collisions to take into account the others reactions which can occured V(r) = U(r) + iW(r) + V so (r) + V c (r) spin-orbite Coulomb

Phenomenogical optical potential 6 He(p,p) 6 He 150 MeV  cm (deg) d  /d  (mb/sr) U(r) = U v f(r) W(r) = W s g(r) + W v f(r) Woods- Saxon R: potential radius a: potential diffusness elastic scattering data: parametrization of U v, W s, W v, a v, a Ws, a Wv, R, V so p-nucleus, n-nucleus interaction: parametrization CH89 from Varner et al. nucleus-nucleus interaction: not general parametrization a projectile on a reduced number of target or limitation in energy. parameters adjusted case by case nuclei in their ground sates !!!!

Microscopic optical potential OpOp OtOt Projectile Target r pt rtrt rprp r pp pp Folding effective nucleon-nucleon force densities  : microscopic or macroscopic densities

Link with ABLA Now: a real potential is used to describe the transmission probability of particles The decay width  for evaporation: another possibility to calculate  capture : optical potentials Kildir et al., PRC 51, 1873 (1995) Aleksandra (nuclei not in their groundstates) E = E imf + E partner + Q +  - B