  Positron and electron cosmic rays provide a complementary way to study the
galactic environment. The actual cosmic rays experiments, for instance PAMELA
and HEAT, have presented very exciting results in this field. The observed
positron fraction appears larger than the actual theoretical predictions for
energies larger than 10 GeV. The indirect evidences of Dark Matter in
connection with Beyond the Standard Model theories would suggest the existence
of an extra contribution present in the cosmic ray signal. We study and
calculate the positron signal produced by the annihilation of a generic Dark
Matter candidate. Especially, We analyze typical annihilation signatures and
the impact of CR propagation physics on the positron signal. In addition, we
study the positron signal related to spallation processes between nuclei
cosmic--rays and the interstellar gas. We analyze the effects of uncertainties
present in nuclear cross section, nuclei cosmic--ray and CR propagation
physics. The propagation of positrons is modeled according to the Two--Zone
Propagation Model which has been successfully tested in the study of nuclei
cosmic--ray and present an analytical approach to study the cosmic--ray
physics.
