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We report first measurements of $e^{+}e^{-}$ pair production in the massregion 0.4 $<M_{ee}<$ 2.6 GeV/$c^{2}$ at low transverse momentum ($p_T<$ 0.15GeV/$c$) in non-central Au$+$Au collisions at $\sqrt{s_{NN}}$ = 200 GeV andU$+$U collisions at $\sqrt{s_{NN}}$ = 193 GeV. Significant enhancement factors,expressed as ratios of data over known hadronic contributions, are observed inthe 40-80% centrality of these collisions. The excess yields peak distinctly atlow-$p_T$ with a width ($\sqrt{\langle p^2_T\rangle}$) between 40 to 60MeV/$c$. The absolute cross section of the excess depends weakly on centralitywhile those from a theoretical model calculation incorporating an in-mediumbroadened $\rho$ spectral function and radiation from a Quark Gluon Plasma orhadronic cocktail contributions increase dramatically with increasing number ofparticipant nucleons. Model calculations of photon-photon interactionsgenerated by the initial projectile and target nuclei describe the observedexcess yields but fail to reproduce the $p^{2}_{T}$ distributions.

Low-$p_T$ $e^{+}e^{-}$ pair production in Au$+$Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U$+$U collisions at $\sqrt{s_{NN}}$ = 193 GeV at STAR