Abnormal dilepton yield from local parity breaking in heavy-ion collisions

Abstract

We propose a novel explanation for the dilepton excess observed in heavy ion collisions at invariant masses below 1 GeV. We argue that the presence of local parity breaking due to a time-dependent isosinglet and/or isotriplet pseudoscalar condensate substantially modifies the dispersion relation of photons and vector mesons propagating in such a medium, changing the \rho~ spectral function and resulting in a potentially large excess of e+e- and \mu+\mu- with respect to the theoretical predictions based in a 'cocktail' of known hadronic processes. Possible signatures to prove or disprove this effect are discussed.