Single ionization of helium by impact of 3.6 MeV u−1 Au53+ ions is investigated by means of quantum-mechanical and classical methods. Calculations of fully differential cross sections are compared with recently published data for ionization of low-energy electrons as a function of the momentum transferred by the projectile to the target system. A description of initial and final states of the He atom in terms of a Hartree-Fock potential provides an improvement over previous hydrogen-like models. The present results show that inclusion of the resolution and uncertainties present in the experiment has a major influence on both the shape and magnitude of the cross sections. The effect of four bodies and electron-electron correlation is also investigated. However, after including the experimental conditions into the calculations, the three- and four-body results present similar behaviour.