Abstract
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 and spin transfer 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: =0 and =0. In particular, our measurement of 〈〉=-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 samples at both beam momenta and Λ¯’s at 18.5 GeV/c prompted a measurement of their analyzing powers, which yielded ()=-0.094±0.012 at 13.3 GeV/c beam momentum and -0.076±0.015 at 18.5 GeV/c, and (Λ¯)=0.03±0.10.
- Received 18 February 1988
DOI:https://doi.org/10.1103/PhysRevD.38.729
©1988 American Physical Society