Total cross sections of charged-current neutrino and anti-neutrino interactions on isoscalar nuclei

New measurements of the total crosssections of charged-current interactions of muonneutrinos and antineutrinos on isoscalar nuclei have been performed. Data were recorded in an exposure of the CHARM detector in an 160 GeV narrow-band beam. The antineutrino flux was determined from the measurements of the pion and kaon flux, and independently from the muon flux measured in the shield; the two methods are found to agree. The neutrino flux was determined from the muon flux ratio forv v runs which was normalized to the antineutrino flux. The cross-section slopes thus are determined. The momentum sum of the quarks in the nucleon and the ratio of sea quark to total quark momentum are derived from the measurements