We have measured the ratios of antiparticles to particles for charged pions
, kaons, and protons near mid-rapidity in central Au + Au collisions at roo
ts(NN) = 130 GeV. We observe (pi (-))/(pi (+)) = 1.00 +/- 0.01(stat) +/- 0.
02(syst), (K-)/(K+) = 0.91 +/- 0.07(stat) +/- 0.06(syst), and [(p) over bar
)/(p) = 0.60 +/- 0.04(stat) +/- 0.06(syst). The (K-)/(K+) and ((p) over bar
)/(p) ratios give a consistent estimate of the baryo-chemical potential mu
(B) of 45 MeV, a factor of 5-6 smaller than in central Pb + Pb collisions a
t roots(NN) = 17.2 GeV.