Charm production by weak neutral currents

Abstract

We discuss quantitatively the production of charm in v N and v N neutral current interactions, and the anomalous lepton events that follow from semi-leptonic charm decay. Diagonal neutral currents, in the Weinberg-Salam model and similar models, predict associated charm production with small cross sections: e.g. σ(v N → vcc − X)/σ(v N → μ − X) ≃ 10 −2 at high energy. The meagre data on vN → ve +X are consistent with a rate of this order. Non-diagonal neutral currents, if present, could give larger cross sections via valence p → c transitions. It should be possible to distinguish diagonal from non-diagonal contributions by their x- or u-dependences, where u = x(1 − y). We calculate the expected energy distributions of the leptons in characteristic vN → vℓ +X and vN → vℓ +ℓ −X charm decay events using simple models, and discuss some practical problems in neutral current measurements.