  Fragmentation reactions induced on light target nuclei by protons and light
nuclei of energies around 1 GeV/nucleon and below are studied with the latest
Los Alamos Monte Carlo transport code MCNP6 and with its cascade-exciton model
(CEM) and Los Alamos version of the quark-gluon string model (LAQGSM) event
generators, version 03.03, used as stand-alone codes. Such reactions are
involved in different applications, like cosmic-ray-induced single event upsets
(SEU's), radiation protection, and cancer therapy with proton and ion beams,
among others; therefore, it is important that MCNP6 simulates them as well as
possible. CEM and LAQGSM assume that intermediate-energy fragmentation
reactions on light nuclei occur generally in two stages. The first stage is the
intranuclear cascade (INC), followed by the second, Fermi breakup
disintegration of light excited residual nuclei produced after INC. Both CEM
and LAQGSM account also for coalescence of light fragments (complex particles)
up to He4 from energetic nucleons emitted during INC. We investigate the
validity and performance of MCNP6, CEM, and LAQGSM in simulating fragmentation
reactions at intermediate energies and discuss possible ways of further
improving these codes.
