We have measured the analyzing power in π+, π−, and KS0 production by a polarized proton beam at 13.3 and 18.5 GeV/c. The data cover the central and the beam fragmentation region, in the transverse-momentum range up to 2 GeV/c. The results indicate that sizable effects are present at high xF and also persist into the hard-scattering region for KS0 and π+. A zero value of the analyzing power was observed for π− production.
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The Brookhaven Alternating Gradient Synchrotron polarized proton beam incident on a beryllium target was used for inclusive Λ production at beam momenta of 13.3 and 18.5 GeV/c. The beam polarization was transverse to the beam direction with magnitude 0.63 at 13.3 GeV/c and 0.40 at 18.5 GeV/c. The Λ polarization was measured and found to be in agreement with results from earlier experiments which used unpolarized proton beams. Analyzing power AN and spin transfer DNN of the Λ’s were both measured and compared with a hyperon-polarization model in which the polarization arises from a Thomas-precession effect. There is good agreement with its predictions: AN=0 and DNN=0. In particular, our measurement of 〈DNN〉=-0.009±0.015 supports the idea that the valence quarks carry all of the hadron spin, since this assumption is implicit in the model’s use of SU(6) wave functions to form final-state hadrons from beam fragments and sea quarks. The presence of substantial KS samples at both beam momenta and Λ¯’s at 18.5 GeV/c prompted a measurement of their analyzing powers, which yielded AN(KS)=-0.094±0.012 at 13.3 GeV/c beam momentum and -0.076±0.015 at 18.5 GeV/c, and AN(Λ¯)=0.03±0.10.
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We have measured the forward production spectra of various neutral particles produced by π−, K−, p¯, and p at 200 GeV/c, and by π− at 290 GeV/c incident on a Be target. The salient features of these measurements are (1) copious production of KSo at large Feynman xL for incident π− and K−, (2) production of roughly equal fluxes of Λ0 and Λ¯0 for incident π−, and (3) close similarity of the following spectra: π−→n and K−→Λ0; π−→Λ0, π−→Λ¯0, and p→KS0; π−→KS0 and p→Λ0. The overall features of the various distributions seem to agree with the ideas of dimensional counting presented in the constituent-interchange model of quark collisions. Results are presented in terms of the invariant cross section Ed3σ(xL, PT=0)dp3 per Be nucleus for each inclusive reaction.
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