ar X iv : n uc l - th / 9 71 10 49 v 2 5 J an 1 99 9 π + Emission from Hypernuclei and the Weak ∆ I = 3 / 2 Transitions

ar X iv : n uc l - th / 9 71 10 49 v 1 2 5 N ov 1 99 7 π + Emission from Hypernuclei and the Weak ∆

Low energy π emission in hypernuclear weak decays is related to ∆I = 3/2 part of nonmesonic weak decays according to the soft pion theorem. We show that neither meson exchange pictures nor virtual Σ excitation can solve the π emission puzzle. On the other hand, the direct quark mechanism gives the ratio R(π/π : S-wave, soft pion) ≈ 1/4 for 4ΛHe and 5ΛHe. ∗email: [email protected]

ar X iv : n uc l - th / 9 71 10 54 v 1 2 6 N ov 1 99 7 The π + – emission puzzle in 4 Λ He decay

We re-examine the puzzling π emission from the weak decay of 4ΛHe and propose an explanation in terms of a three–body decay of the virtual Σ. Such a resolution of the π decay puzzle is consistent with the calculated Σ probability in light Λ hypernuclei as well as the experimentally observed π energy spectrum and s–wave angular distribution. Typeset using REVTEX

X iv : n uc l - th / 9 41 10 19 v 3 2 J an 1 99 5 DOUBLE ∆ PRODUCTION IN THE γd → pnπ + π − REACTION

ar X iv : n uc l - th / 9 90 50 49 v 2 2 6 M ay 1 99 9 η - and η ′ - meson production in the reaction pn → dM near threshold

ar X iv : n uc l - th / 9 90 50 49 v 1 2 1 M ay 1 99 9 η - and η ′ - meson production in the reaction pn → dM near threshold