  The possibility of proton acceleration to very high energies in astrophysical
sources may have unique observational consequences. In particular, the decay of
secondary mesons created in the interaction of energetic protons with photons
or nucleons gives rise to high-energy gamma rays and neutrinos with potentially
observable fluxes. Recently, there has been considerable interest in the
parameterization of the energy spectra of these secondaries. Less attention has
been paid to the angular distributions, which may have an important effect on
observational quantities and are required to address collisions between protons
with different energies and an arbitrary scattering angle. In this work, we
study the complete particle distributions of secondary mesons created in
proton-proton collisions. We present parameterizations of the energy and
rapidity distributions of secondary pions and kaons that reproduce results
generated with the event generator PYTHIA to within ~10% in the bulk of the
parameter space. The parameterizations are based on incident proton energies
from 1 TeV to 1 PeV and are suited for extrapolation to higher energies. We
present several applications of these parameterizations. Energy spectra and
angular distributions of stable decay products (electrons, neutrinos and gamma
rays) follow readily. We give an example of the gamma-ray spectrum that results
from the decay of pi0 mesons created in a proton-proton collision. We show that
there is a strong correlation between the energy of secondary mesons and the
degree of collimation around the direction of the colliding protons. This
effect may have important implications for the detection possibility of
neutrinos created in the interaction of a developing GRB with its surroundings.
