Electron pair creation in π+p capture reactions from rest

Abstract

Electromagnetic corrections are calculated for the processes π−+p→n+e++e− and π0→γ+e++e−. These corrections depend on the c.m. energy of the pair. For very low c.m. energy the corrections are relatively large, and due mainly to the electron-positron Coulomb attraction; they fall rapidly with increasing c.m. energy to a minimum of 0.5%, then rise slowly to a value of 1.7% at the highest c.m. energy. For both processes, the correction to the total rate amounts to about 1%. In terms of these total rates, the Panofsky ratio is found to be $$R_P = 0.594P[\pi ^ - + p \to n + \pi ^0 ,\pi ^0 \to \gamma + e^ + + e^ - ]/P[\pi ^ + + p \to n + e^ + + e^ - ].$$ . For the process π−+p→n+e++e−, the problem of empirically identifying the contributions arising from interaction via the longitudinal component of the electromagnetic field and from size effects is discussed. These contributions are expected to amount to only 2.0% and 0.8%, respectively, of the total rate. The process π−+p→n+2γ is also discussed briefly.