A three-dimensional calculation of atmospheric neutrino fluxes

We present a three-dimensional (3-D) calculation of atmospheric neutrino fluxes using accurate models of the geomagnetic field, hadronic interactions, tracking and decays. Results are presented for the Super-Kamiokande and Sudbury Neutrino Observatory sites using the GEANT-FLUKA hadronic code. We make a comparison with previous one-dimensional calculations and other 3-D results. The recently reported geometrical enhancement of low energy, horizontal neutrinos is confirmed. The effect on observed leptons is however, restricted to a small overall increase in flux. We report east–west asymmetries for each of the neutrino species.