With the help of the density operator, the angular differential cross-section for ionization of helium is calculated within the framework of the one-centre atomic-orbital close-coupling method. We consider a naked C6+ ion as projectile with an energy of 2.5 MeV/a.u. Our result agrees well with the experimental data and the other theoretical calculations such as the first Bo approximation, various Distorted Wave models and the classical trajectory Monte Carlo simulation.