HARP: a hadron production experiment for the neutrino factory and for the atmospheric neutrino flux

The HARP experiment will carry out, at the CERN PS, a large programme of measurements of secondary hadron production, over the full solid angle, produced on thin and thick nuclear targets by beams of protons and pions with momenta in the range 2 to 15 GeV/c. The first aim of the experiment is to acquire adequate knowledge of pion yields for an optimal design of the recently proposed neutrino factory. The second aim is to reduce substantially the existing ~30% uncertainty in the calculation of absolute atmospheric neutrino fluxes and the ~7% uncertainty in the ratio of neutrino flavours. (15 refs).