NA61/SHINE is a unique spectrometer for the measurement of hadronic
interactions at fixed-target energies that are of particular interest
for cosmic ray physics.
In this talk we will present the final results from our 2009
data-taking campaign on particle production in pi^- + C interactions
at 158 and 350 GeV/c. These interactions are relevant to understand
the final stages of ultrahigh-energy cosmic-ray air showers. Our
measurements include the production of pions, kaons, (anti-)protons
and rho mesons. We will discuss the impact of these results on the
interpretation of cosmic-ray data.
Furthermore we will report on new data on the fragmentation of carbon
nuclei. A one week pilot run with data taking of carbon on
polyethylene and carbon at a beam energy of 13 GeV/nucleon took place
at the end of of 2018. The aim of this run was to demonstrate
capabilities of the experiment to perform high-precision measurements
of nuclear fragmentation cross sections needed for the understanding of
secondary-to-primary cosmic-ray flux ratios, such as the
boron-to-carbon ratio. Preliminary results on the data quality and
identification of beam nuclei and fragmented nuclei will be presented.