PION PAIR PRODUCTION FROM 77 COLLISIONS AT THE SLAC e + e - STORAGE RING PEP

We have studied several features of the production of charged hadron pairs by qy collisions. We have measured the j” partial width I”,,,(Q2) for & in the range 0 < Q2 < 1.4 Gep/c2, and obtained $.,rr = 2.52 f 0.13 f 0.38 keV at q2 = 0. The measured Q2 dependence is in agreement with the generalized vector dominance model. The cross section for 77 ---) (?r+n+ K+K-) in the mass region 1.6 GeV/c2 < M nn < 2.5 GeV/c2 has also been measured and the result compared with that expected from the QCD continuum. Submitted to Physical Review D * This work was supported in part by the Department of Energy, contracts DEAC0376SFOO515 (SLAC), DEAC0376SFOOO98 (LBL) and DEAC02-76ER03064 (Harvard). Support for individuals also is from U.C. Davis, and NSF.