Experimental study of differential cross-sections dsigma/dy in neutral current neutrino and antineutrino interactions

The authors present differential cross sections d sigma /dy corrected for resolution and acceptance, for events induced by both the neutral- and charged-current interactions of neutrinos and antineutrinos. They are based on 8553 neutrino and 3578 antineutrino events obtained using the CHARM fine-grain calorimeter in the CERN 200 GeV narrow-band beam. From these differential cross sections they demonstrate that the coupling strength of the weak neutral current to the strange quark is compatible with being equal to that of the down quark. Assuming this equality they then describe the weak neutral current in terms of one parameter, sin/sup 2/ theta , which they find to be 0.222+or-0.016. The charged-current differential cross sections yield values of the fractional momentum-weighted content of the nucleon for non-strange (0.12+or-0.04) and strange (0.06+or-0.04) sea quarks. Furthermore, from the strength of the allowed y/sup 2/ term in the neutral-current differential cross sections they put a limit of 3% on the presence of scalar or pseudoscalar contributions to the weak neutral current. This can alternatively be expressed in terms of the Callan-Gross violation parameter R, where they find R=0.10+or-0.10. (18 refs).