  We have measured the ratios of antiparticles to particles for charged pions,
kaons and protons near mid-rapidity in central Au+Au collisions at sqrt(s_NN) =
130 GeV. For protons, we observe pbar/p = 0.60 +/- 0.04 (stat.) +/- 0.06
(syst.) in the transverse momentum range 0.15 < p_T < 1.0 GeV/c. This leads to
an estimate of the baryo-chemical potential mu_B of 45 MeV, a factor of 5-6
smaller than in central Pb+Pb collisions at sqrt(s_NN) = 17.2 GeV.
