Can transport peak explain the low-mass enhancement of dileptons at   RHIC?
  We propose a novel relation between the low-mass enhancement of dielectrons observed at PHENIX and transport coefficients of QGP such as the charge diffusion constant $D$ and the relaxation time $\tau_{\rm J}$. We parameterize the transport peak in the spectral function using the second-order relativistic dissipative hydrodynamics by Israel and Stewart. Combining the spectral function and the full (3+1)-dimensional hydrodynamical evolution with the lattice EoS, theoretical dielectron spectra and the experimental data are compared. Detailed analysis suggests that the low-mass dilepton enhancement originates mainly from the high-temperature QGP phase where there is a large electric charge fluctuation as obtained from lattice QCD simulations. 
Yukinao Akamatsu, Hideki Hamagaki, Tetsuo Hatsuda, Tetsufumi Hirano
nucl-th hep-ph nucl-ex