The role of on-site correlation in the low-energy excitations of nickel is
studied by comparing the results of high-angular and high-energy resolution
photoemission spectroscopy with quasiparticle states calculated as a three
-body scattering solution of a multiorbital Hubbard model. It is found that
correlation effects modify the energy dispersion and spin polarization of
electron states and are essential in order to get a quantitative agreement
with experimental data.