X iv : n uc l - th / 9 90 10 05 v 1 4 J an 1 99 9 Study of correlation of production and decay planes in π → 3 π diffractive dissociation process on nuclei ∗

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 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

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

Low energy π emission in hypernuclear weak decays is studied in the soft pion limit. It is found that the π decay amplitude is dominated by the ∆I = 3/2 part of nonmesonic weak decays according to the soft pion theorem. The ratios, R(π/soft π−), for light hypernuclei are estimated in the direct quark mechanism, which predicts violation of the ∆I = 1/2 rule, and found to be about 1/3 for 4ΛHe. ∗...

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 50 70 01 v 1 3 J ul 1 99 5 Subthreshold K + Production on Nuclei by π + Mesons

The inclusive K + mesons production in π + –nucleus reactions in the subthreshold energy regime is analyzed with respect to the one–step (π + n → K + Λ) and the two– step (π + n → ηp 1 , ηp 2 → K + Λ) incoherent production processes on the basis of an appropriate folding model, which allows one to take into account the various forms of an internal nucleon momentum distribution as well as on– an...