THEORY OF DOUBLY RADIATIVE PI-CAPTURE IN NUCLEI

A detailed theory is developed for the nuclear (π-, 2γ) capture process assuming a normal nucleus with no anomaly due to the meson field. An effective hamiltonian is constructed from the individual gauge invariant nucleonic process. Branching ratio and angular correlations are calculated using the closure approximation and a realistic shape of the nuclear excitation spectrum. It is shown that the atomic 1s capture is particularly sensitive to pion effects, while the 2p atomic capture is dominated by the bremsstrahlung of single radiative capture. Explicit numerical results are given for 12C and compared with recent experimental work. While the branching ratio agrees, a qualitative discrepancy is found in backward angular shape. © 1979.