  As neutrino long baseline experiments enter a new domain of precision,
important systematic errors due to poor knowledge of production cross-sections
for pions and kaons require more dedicated measurements for precise neutrino
flux predictions. The cosmic ray experiments require dedicated hadron
production measurements to tune simulation models used to describe air shower
profiles. Among other goals, the NA61-SHINE (SPS Heavy Ion and Neutrino
Experiment) experiment at the CERN SPS aims at precision measurements (5% and
below) for both neutrino and cosmic ray experiments: those will improve the
prediction of the neutrino flux for the T2K experiment at J-PARC and the
prediction of muon production in the propagation of air showers for the Auger
and KASCADE experiments. Motivations for new hadron production measurements are
briefly discussed. NA61-SHINE took data during a pilot run in 2007 and in 2009
with different Carbon targets. The NA61-SHINE setup and preliminary spectra for
positive and negative pions obtained with the 2007 thin (4% interaction length)
Carbon target data are presented. The use of the NA61 data for the T2K neutrino
flux predictions is finally discussed in further details.
