Thermal dilepton production from droppingρbased on the vector manifestation

Abstract

We study the pion electromagnetic form factor and the dilepton production rate in hot matter using the hidden local symmetry theory as an effective field theory for pions and $\ensuremath{\rho}$ mesons. In this framework, the chiral symmetry restoration is realized as the vector manifestation (VM) in which the massless vector meson becomes the chiral partner of the pion, giving a theoretical support to the dropping $\ensuremath{\rho}$ \`a la Brown-Rho scaling. In the VM, the vector dominance (VD) is strongly violated near the phase transition point associated with the dropping $\ensuremath{\rho}$. We show that the effect of the violation of the VD substantially suppresses the dilepton production rate compared with the one predicted by assuming the VD together with the dropping $\ensuremath{\rho}$.