(eng)
Measurements of double-differential charged pion production cross-sections in
interactions of 12 GeV/c protons on O_2 and N_2 thin targets are presented in
the kinematic range 0.5 GeV/c < p_{\pi} < 8 GeV/c and 50 mrad < \theta_{\pi} <
250 mrad (in the laboratory frame) and are compared with p--C results. For
p--N_2 (p--O_2) interactions the analysis is performed using 38576 (7522)
reconstructed secondary pions. The analysis uses the beam instrumentation and
the forward spectrometer of the HARP experiment at CERN PS. The measured
cross-sections have a direct impact on the precise calculation of atmospheric
neutrino fluxes and on the improved reliability of extensive air shower
simulations by reducing the uncertainties of hadronic interaction models in the
low energy range. In particular, the present results allow the common
hypothesis that p--C data can be used to predict the p--N_2 and p--O_2 pion
production cross-sections to be tested.
