Analyzing power in inclusive π0 production at high xF with 185 GeV/c polarized proton and antiproton beams

We present first results for the analyzing power AN in inclusive π0 production obtained using the new 185 GeV/c Fermilab polarized proton and antiproton beams. We obtain a value AN(p→π0)=0.10±0.03 in the kinematic region 0.2<xF<0.8 and 0.3<pT<1.2 GeV/c. An interpretation of this result using a simple parton recombination model suggests that the spin of the proton is carried by its valence quarks