The ${\pi }^{+}$--emission puzzle in ${}_{\Lambda }^4$He decay

Abstract

We re-examine the puzzling ${\pi }^{+}$ emission from the weak decay of ${}_{\Lambda }^4$He and propose an explanation in terms of a three-body decay of the virtual ${\Sigma }^{+}$. Such a resolution of the ${\pi }^{+}$ decay puzzle is consistent with the calculated ${\Sigma }^{+}$ probability in light $\Lambda$ hypernuclei as well as the experimentally observed ${\pi }^{+}$ energy spectrum and $s$--wave angular distribution.

Comments: 16 pages, Revtex, 2 figures, amstex and amssymb style files