  Interaction cross sections and charged pion spectra in p+C interactions at 31
GeV/c were measured with the large acceptance NA61/SHINE spectrometer at the
CERN SPS. These data are required to improve predictions of the neutrino flux
for the T2K long baseline neutrino oscillation experiment in Japan. A set of
data collected during the first NA61/SHINE run in 2007 with an isotropic
graphite target with a thickness of 4% of a nuclear interaction length was used
for the analysis. The measured p+C inelastic and production cross sections are
257.2 +- 1.9 +- 8.9 mb and 229.3 +- 1.9 +- 9.0 mb, respectively. Inclusive
production cross sections for negatively and positively charged pions are
presented as a function of laboratory momentum in 10 intervals of the
laboratory polar angle covering the range from 0 up to 420 mrad. The spectra
are compared with predictions of several hadron production models.
