Quark charge retention in final state hadrons from deep inelastic muon scattering

The net charge of final state hadrons in both the current and target fragmentation regions has been measured in 280 GeV/ c muon-proton scattering experiment. A clean kinematic separation of the two regions in the centre-of-mass rapidity is demonstrated. The dependence on x Bj of the mean net charges is found to be consistent with a large contribution of sea quarks at small x Bj and with the dominance of valence quarks at large x Bj thus giving clear confirmation of the quarck- parton model. It is also shown that the lending forward hadron has a high probability of containing the struck quark.