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

Le résumé fourni par la source

We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via ${e}^{+}{e}^{\ensuremath{-}}$ decays, from $\sqrt{s}=200$ 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 $\ensuremath{\omega}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ invariant yields are consistent with previous measurements. The mid-rapidity yields ($d\phantom{\rule{-0.16em}{0ex}}N/dy$) of $\ensuremath{\varphi}$ and $J/\ensuremath{\psi}$ are extracted through their di-electron decay channels and are consistent with the previous measurements of $\ensuremath{\varphi}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$ and $J/\ensuremath{\psi}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$. Our results suggest a new upper limit of the branching ratio of the $\ensuremath{\eta}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ of $1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at the 90$%$ confidence level.

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