Dilepton anisotropy from p + Be and Ca + Ca collisions at BEVALAC energies

A full calculation of lepton-pair angular characteristics is carried out for e+e− pairs created in p + Be and Ca + Ca collisions from 1.0 to 2.1 GeV/A. It is demonstrated that the dilepton decay anisotropy depends sensitively on the different sources and may be used for disentangling them. Due to the dominance of the η- and Δ-Dalitz decays and only a small anisotropy coefficient for π+π− annihilation, the expected anisotropy coefficients show a decrease with invariant mass of the dilepton pair and change only moderately when comparing p + Be and Ca + Ca reactions at the same bombarding energy.