  Emission of light fragments (LF) from nuclear reactions is an open question.
Different reaction mechanisms contribute to their production; the relative
roles of each, and how they change with incident energy, mass number of the
target, and the type and emission energy of the fragments is not completely
understood.
  None of the available models are able to accurately predict emission of LF
from arbitrary reactions. However, the ability to describe production of LF
(especially at energies $\gtrsim 30$ MeV) from many reactions is important for
different applications, such as cosmic-ray-induced Single Event Upsets (SEUs),
radiation protection, and cancer therapy with proton and heavy-ion beams, to
name just a few. The Cascade-Exciton Model (CEM) version 03.03 and the Los
Alamos version of the Quark-Gluon String Model (LAQGSM) version 03.03 event
generators in Monte Carlo N-Particle Transport Code version 6 (MCNP6) describe
quite well the spectra of fragments with sizes up to $^{4}$He across a broad
range of target masses and incident energies (up to $\sim 5$ GeV for CEM and up
to $\sim 1$ TeV/A for LAQGSM). However, they do not predict the high-energy
tails of LF spectra heavier than $^4$He well. Most LF with energies above
several tens of MeV are emitted during the precompound stage of a reaction. The
current versions of the CEM and LAQGSM event generators do not account for
precompound emission of LF larger than $^{4}$He.
  The aim of our work is to extend the precompound model in them to include
such processes, leading to an increase of predictive power of LF-production in
MCNP6. Extending our models to include emission of fragments heavier than
$^4$He at the precompound stage has already provided preliminary results that
have much better agreement with experimental data.
