Measurement of the $W \to e ��$ and $Z/��^* \to e^+e^-$ Production Cross Sections at Mid-rapidity in Proton-Proton Collisions at $\sqrt{s}$ = 500 GeV

We report measurements of the charge-separated $W^{+(-)} \to e^{+(-)} + ��_e(\bar��_e)$ and $Z/��^* \to e^+e^-$ 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 $e ��$ channel were measured to be $��(pp \to W^+ X) \cdot BR(W^+ \to e^+ ��_e)$ = 117.3 \pm 5.9(stat) \pm 6.2(syst) \pm 15.2(lumi) pb, and $��(pp \to W^- X) \cdot BR(W^- \to e^- \bar��_e)$ = 43.3 \pm 4.6(stat) \pm 3.4(syst) \pm 5.6(lumi) pb. For $Z/��^*$ production, $��(pp \to Z/��^* X) \cdot BR(Z/��^* \to e^+ e^-)$ = 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, $��(pp \to W^+ X) / ��(pp \to W^- X)$, 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.
14 pages, 12 figures, submitted to Physical Review D