${\pi }^{+}$ Emission from Hypernuclei and the Weak $\Delta I=3/2$ Transitions

Abstract

Low energy ${\pi }^{+}$ emission in hypernuclear weak decays is studied in the soft pion limit. It is found that the ${\pi }^{+}$ decay amplitude is dominated by the $\Delta I=3/2$ part of nonmesonic weak decays according to the soft pion theorem. The ratios, $R({\pi }^{+}/soft{\pi }^{-})$, for light hypernuclei are estimated in the direct quark mechanism, which predicts violation of the $\Delta I=1/2$ rule, and found to be about 1/3 for ${}_{\Lambda }^{4}He$.

Comments: 13 Pages, 2 Figures