HIGH-PRECISION MEASUREMENT OF THE ANALYZING POWER IN LARGE-P-PERPENDICULAR-TO-2 SPIN-POLARIZED 24-GEV/C PROTON-PROTON ELASTIC-SCATTERING

We measured the analyzing power A out to P perpendicular-to 2 = 7.1 (GeV/c)2 with high precision by scattering a 24-GeV/c unpolarized proton beam from the new University of Michigan polarized proton target; the target's 1-W cooling power allowed a beam intensity of more than 2 x 10(11) protons per pulse. This high beam intensity together with the unexpectedly high average target polarization of about 85% allowed unusually accurate measurements of A at large P perpendicular-to 2. These precise data confirmed that the one-spin parameter A is nonzero and indeed quite large at high P perpendicular-to 2; most theoretical models predict that A should go to zero.