Di-electron spectrum at mid-rapidity in p+p collisions at s=200 GeV

We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e⁺e^- decays, from s=200 GeV p+p collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted ω→e⁺e^- invariant yields are consistent with previous measurements. The mid-rapidity yields (dN/dy) of φ and J/ψ are extracted through their di-electron decay channels and are consistent with the previous measurements of φ→K⁺K^- and J/ψ→e⁺e^-. Our results suggest a new upper limit of the branching ratio of the η→e⁺e^- of 1.7×10^-5 at the 90% confidence level.