Measurement of Panofsky Ratio: Nuclear Absorption ofπ−fromKShell in Hydrogen

The ratio of charge exchange to radiative capture in hydrogen for stopped ${\pi }^{-}$ mesons has been determined by measuring the total photon spectrum in a lead glass Čerenkov counter. The ratio was found to be 1.87 ±0.10. Possible contribution from in-flight pions has been shown to be quite small. The error has been estimated including this effect, as well as errors related to total number of events observed, and errors arising in the data analysis. Evidence for high-energy photon production by capture of slow ${\pi }^{-}$ in elements other than hydrogen is discussed.