The analyzing power AN in inclusive π0 production has been measured with use of the new 185-GeV/c Fermilab polarized proton beam. We obtain the value AN=0.10±0.03 for π0's in the kinematic region 0.2<xF<0.8 and 0.3<pT<1.2 GeV/c. In certain models of particle production this suggests that the spin of the proton is carried by its valence quarks.
A measurement of the single-spin asymmetry A N in p↑ + p→ π 0 + X at 200 GeV with x F = 0 shows a transition in the production process from a “ low -x T ” regime with A N = 0, through an intermediate region of negative asymmetry, to a “ high -x T ” regime with A N > 0.3. This transition occurs at x T ≈ 0.4 and is consistent with x T -scaling of A N in pion production using polarized beams or targets from √− s =5.2 to 19.4 GeV. Results for A N in η production by polarized protons and in π 0 production by polarized antiprotons are also presented.
The analyzing power in inclusive charged pion production has been measured using the 200 GeV Fermilab polarized proton beam. A striking dependence in x F is observed in which A N increases from 0 to 0.42 with increasing x F for the π + data and decreases from 0 to −0.38 with increasing x F for π − data. The kinematic range covered is 0.2⩽ x F ⩽0.9 and 0.2⩽ p T ⩽2.0 GeV / c . In a simple model our data indicate that at large x F the transverse spin of the proton is correlated with that of its quark constituents.
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The spin asymmetryAN for inclusive π0 production by 200-GeV transversely-polarized protons on a liquid hydrogen target has been measured at Fermilab over a wide range ofxF, with 0.5<pT<2 GeV/c. AtxF>0.3, the asymmetry rises with increasingxF and reaches a value ofAN=0.15±0.03 in the region 0.6<xF<0.8. This result provides new input regarding the question of the internal spin structure of transversely-polarized protons.