System-size and energy dependences of dielectron excess invariant mass spectra at STAR

We present the systematic study of dielectron production in U + U collisions at sNN=193 GeV by Solenoidal Tracker At RHIC (STAR) experiment. Invariant mass, transverse momentum, and centrality differential measurements of dielectron yields are compared to Monte-Carlo hadronic contributions excluding ρ-meson. In each comparison, there is an excess in the Low Mass Region (LMR) that can be described by a model calculation including a broadened ρ spectral function. With detector acceptance correction applied, the dielectron excess invariant mass spectra in U + U collisions at sNN=193 GeV and in Au + Au collisions at sNN=27,39, and 62.4 GeV are reported. System-size and energy dependences of low mass excess yield are discussed together with model comparisons.