Q2-dependence of backward pion multiplicity in neutrino–nucleus interactions

The production of pions emitted backward in inelastic neutrino–nucleus interactions is analyzed within the impulse approximation in the framework of the dual parton model. We focus on the Q2-dependence of the multiplicity of negative pions, normalized to the total cross section of the reaction ν+A→μ+X. The inclusion of planar (one-Reggeon exchange) and cylindrical (one-Pomeron exchange) graphs leads to a multiplicity that decreases as Q2 increases, in agreement with recent measurements carried out at CERN by the NOMAD Collaboration. A realistic treatment of the high momentum tail of the nucleon distribution in a nucleus also allows for a satisfactory description of the semi-inclusive spectrum of backward pions.