Angular differential and elemental fragmentation cross sections of a 400 MeV/nucleon O16 beam on a graphite target with the FOOT experiment

This paper presents the measurements of the angular differential cross sections for the forward production of He, Li, Be, B, C, and N nuclei in the fragmentation process of a 400 MeV/nucleon 16O beam interacting with a graphite target. Due to the limited data available in this energy regime, these measurements of nuclear fragmentation cross sections are relevant to improve nuclear interaction models for particle therapy and space radioprotection applications. The data analyzed in this paper were collected during a measurement campaign carried out at the GSI Helmholtz Center for Heavy Ion Research facility in Darmstadt (Germany) by the FOOT Collaboration. The results are compared with similar results found in the literature and with a previous FOOT measurement of the same process, using the same setup, from a previous pilot run performed at GSI. The pilot run data, however, had limited statistics and only allowed for the measurement of elemental fragmentation cross sections integrated in the setup acceptance. This data set, with statistics more than 100 times larger compared to the data collected in the previous run, enabled the measurement of angular differential cross sections, fully exploiting the granularity of the FOOT AE-TOF (time-of-flight) system. Furthermore, a better comprehension of the FOOT apparatus allowed to improve the analysis techniques, leading to a reduction in the final systematic uncertainties. The cross section results have been compared with some of the prominent Monte Carlo models of FLUKA and Geant4 dedicated to the energy range of interest for light ion fragmentation physics.