Dilepton as a probe of pion dynamics in heavy-ion collisions

Modeling heavy-ion collisions by an expanding fireball, we calculate the dilepton production cross section including contributions from both the nucleon-nucleon interactions and the pion-pion annihilations. For the pion, we take into account the medium polarization effect on its dispersion relation. We find that dilepton production at large invariant masses is dominated by the latter process and thus is a viable probe to the pion dynamics in heavy-ion collisions.