Electron capture to the continuum by proton and positron impact

We describe recent experimental triple-differential cross sections of ioniz ation by the impact of both protons and positrons by means of a single, kin ematically exact theory. This model incorporates all the interactions in th e final state on an equal footing and keeps an exact account of the three-b ody kinematics. We show that these provisions make it possible to evaluate any multiple-differential cross section for any given mass configuration, a nd analyse how it changes with the relative masses of the three particles i n the final state. We analyse the differences in the electron cusp formatio n by both heavy and light projectile impact at the double-differential cros s section level.