| Abstract: | We report measurements of the charge-separated $W^{+(-)} o e^{+(-)} +
u_e(ar{
u}_e)$ and $Z/gamma^* o e^+e^-$ 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 $sigma(pp o W^+ X) cdot BR(W^+ o e^+
u_e)$ = 117.3
pm 5.9(stat) pm 6.2(syst) pm 15.2(lumi) pb, and $sigma(pp o W^- X) cdot
BR(W^- o e^- ar{
u}_e)$ = 43.3 pm 4.6(stat) pm 3.4(syst) pm 5.6(lumi)
pb. For $Z/gamma^*$ production, $sigma(pp o Z/gamma^* X) cdot
BR(Z/gamma^* o e^+ e^-)$ = 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, $sigma(pp o W^+
X) / sigma(pp o W^- X)$, 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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