We report measurements of the charge-separated $W^{+(-)} to e^{+(-)} + u_e(bar{ u}_e)$ and $Z/gamma^* to e^+e^-$ production cross sections at mid-rapidity in proton-proton collisions at $sqrt{s}$ = 500 GeV. These results are based on 13.2 pb$^{-1}$ of data recorded in 2009 by the STAR detector at RHIC. Production cross sections for W bosons that decay via the $e u$ channel were measured to be $sigma(pp to W^+ X) cdot BR(W^+ to e^+ u_e)$ = 117.3 pm 5.9(stat) pm 6.2(syst) pm 15.2(lumi) pb, and $sigma(pp to W^- X) cdot BR(W^- to e^- bar{ u}_e)$ = 43.3 pm 4.6(stat) pm 3.4(syst) pm 5.6(lumi) pb. For $Z/gamma^*$ production, $sigma(pp to Z/gamma^* X) cdot BR(Z/gamma^* to e^+ e^-)$ = 7.7 pm 2.1(stat) $^{+0.5}_{-0.9}$(syst) pm 1.0(lumi) pb for di-lepton invariant masses $m_{e^+e^-}$ between 70 and 110 GeV/$c^2$. First measurements of the W cross section ratio, $sigma(pp to W^+ X) / sigma(pp to W^- X)$, at $sqrt{s}$ = 500 GeV are also reported. Theoretical predictions, calculated using recent parton distribution functions, are found to agree with the measured cross sections.
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