High Energy Physics Division semiannual report of research activities, January 1, 1999--June 30, 1999.

In the period January--June 1999 accomplishments for the ANL-HEP division medium energy physics project consisted of the completion of two papers on past Saclay experiments, the beginning of analysis of recent data from the Crystal Ball measurements at the Brookhaven AGS, and preparations for a RHIC polarimeter. Two papers on Saclay pp elastic scattering data were completed by an ANL physicist, submitted and accepted in Physical Review. Results for the spin observable P - A{sub oono} = A{sub ooon} = A{sub y} at over 30 beam kinetic energies between 800 and 2,800 MeV and C.M. angles from about 70{degree}--110{degree} are described. A total of 919 new data points are presented in these articles. The energy dependence at fixed c.m. angles appears smooth, with no evidence for rapid energy-dependent structure. Work has also begun on two additional papers at Argonne and on others at Saclay.