  The theoretical Monte Carlo calculations of the production of neutrinos via
cosmic rays incident upon the earth's atmosphere are examined. The calculations
are sensitive to the assumed ratio of pi+ / pi- production cross sections; this
ratio appears to be underestimated in the theory relative to the experimentally
measured ratio. Since the neutrino detection cross section is three times
larger than that for the antineutrino, the theoretical predicted detection
ratio (nu_mu / nu_e) is correspondingly too large.
