Pair production in hydrogen and the Panofsky ratio

Abstract

Observations are reported of some 1600 pair and triplet production events in which the conversion occurs in the hydrogen filling of a 10-inch bubble chamber. The γ’s responsible for the events are all identified as originating from charge exchange and radiative capture reactions of π-mesons stopping in the same bubble chamber. The number of π− stops, the number of pairs and triplets separated as to source, along with a Monte Carlo calculation of geometrical factors, allows a determination of the Panofsky ratio and the constantAtrip in the assumed form of the triplet cross-section σtrip. The results areP=1.590±0.089 for the Panofsky ratio andAtrip=(109±5.4)/9. The best theoretical estimate forAtrip is 105/9 with an uncertainty of about 5/9.