Charged antiparticle to particle ratios near midrapidity in p+p   collisions at sqrt(s_NN)=200 GeV
  The ratios of the yields of primary charged antiparticles to particles have been obtained for pions, kaons, and protons near midrapidity for p+p collisions at sqrt(s_NN) = 200 GeV. Ratios of <pi-/pi+>=1.000 +/- 0.012 (stat.) +/- 0.019 (syst.), <K-/K+>=0.93 +/- 0.05 (stat.) +/- 0.03 (syst.), and <pbar/p>=0.85 +/- 0.04 (stat.) +/- 0.03 (syst.) have been measured. The reported values represent the ratio of the yields averaged over the rapidity range of 0.1<y_{pi}<1.3 and 0<y_{K,p}<0.8, and for transverse momenta of 0.1<p_T^{pi,K}<1.0 GeV/c and 0.3<p_T^{p}<1.0 GeV/c. Within the uncertainties, all three ratios are consistent with the values measured in d+Au collisions at the same energy. The data are compared to results from other collision systems and energies. 
the PHOBOS Collaboration: B.B. Back, et al