The Internal Pair Production ofγ-Rays of Mesonic Origin; Alternate Modes ofπ0Decay

The internal pair creation of the $\gamma$-rays in the processes (1) ${\pi }^0\to \gamma +\gamma ,$ (2) ${\pi }^{-}+P\to \gamma +N$ has been observed. The experimental conversion coefficient $\beta =0.0080\mathrm{}\pm 0.0016$ is to be compared to the theoretical prediction, 0.0063. In addition, we have obtained an upper limit on the fraction of neutral pions which decay directly into a pair: ${\pi }^0\to e^{+}+e^{-}$. The limit is one in 2000.