400 GeV proton-induced prompt neutrinos at 0 and 15 milliradian

The experiments in three neutrino detectors (heavy liquid bubble chambers BEBC and Gargamelle, CDHSB iron plate -scintillator calorimeter) made with the 400 GeV SPS proton beam dumped into a massive copper target and the 'skew beam dump' experiment (wrong-sign lepton events in the BEBC narrow-band antineutrino beam experiment) are reviewed. From the observations - more electron events than explainable by electron neutrinos from conventional sources (K, Λ, Σ) - prompt neutrino fluxes can be derived. If these are interpreted as due to production (approximately Asup(2/3)) and semi-leptonic decay (Kstar eν, 10% branching ratio) of charmed particles (D-mesons) which do not re-interact inside the nucleus, then cross sections for pp → D anti-D + anything of 100-200 μb (BEBC, Gargamelle) or about 40 μb (CDHSB) are required, the discrepancy not being understood. If linear A-dependence is assumed, the cross sections would be four times smaller; if (pion-like) re-scattering of D's is assumed, the cross sections could be up to two times larger. Other interpretations are briefly discussed. (author)