Accession Number : AD0618661

Title :   PION-PAIR PHOTOPRODUCTION BELOW 1 BEV,

Corporate Author : STANFORD UNIV CALIF HIGH ENERGY PHYSICS LAB

Personal Author(s) : Allaby,J. V. ; Lynch,H. L. ; Ritson,D. M.

Report Date : MAY 1965

Pagination or Media Count : 17

Abstract : Measurements of the differential cross-section for the reaction gamma + p to pion (-) + pion (+) + p have been made at several angles for photon energies in the range 550-1000 MeV, using the Stanford Mark III linear accelerator. The pion(-) were detected and momentum analyzed using a 90 degree magnetic spectrometer. It was found that the reaction was dominated by the pseudo-2-body photoproduction gamma + p to pion (-) + N* (1238) especially near the threshold for this process. At low momenta, the pion(-) were identified by range. At high momenta (>250 MeV/c), the contaminating electrons were eliminated by using a lead and scintillation-counter sandwich system. The yields of both pion (-) and pion (+) off hydrogen were measured and the normalization was obtained by comparing with the known cross-sections for gamma + p to pion (+) + n. Computer calculations of the shapes of the yield curves expected from 2-body and 3-body production enabled the data to be separated into the two possible states gamma + p to pion (-) + N* (1238) and gamma + p to pion (-) + pion (+) + p. Angular distributions and total cross-sections are presented. (Author)

Descriptors :   (*GAMMA PROTON REACTIONS, PAIR PRODUCTION), (*PAIR PRODUCTION, PIONS), MESON CROSS SECTIONS, DIFFERENTIAL CROSS SECTIONS

Distribution Statement : APPROVED FOR PUBLIC RELEASE