Mean Lifetime of theπ0Meson

Abstract

An estimate of the ${\pi }^0$ mean lifetime has been obtained by a method first attempted by Harris, Orear, and Taylor in 1957. The decay distances of monoenergetic ${\pi }^0$ mesons, produced by the $K_{\pi 2}$ decay at rest ($K^{+}\to {\pi }^{+}+{\pi }^0$) and decaying via the Dalitz mode (${\pi }^0\to e^{+}+e^{-}+\gamma$), were measured. In two stacks of nuclear emulsion (Ilford K5), exposed to the 700-MeV/c $K^{+}$ beam at the Berkeley Bevatron, 45 events of this type were found. For the ${\pi }^0$ mean lifetime a value of $\tau =\left({{2.3}_{-1.0\mathrm{}}}^{+1.1\mathrm{}}\right)\times {10}^{-16\mathrm{}}$ sec has been obtained.