On the production mechanism of Sigma-hypernuclear systems in A(K-, pi(+/-)) reactions

It is shown that the new data on the excitation energy E-exc spectrum of th e residual nuclear system in the Sigma-hypernuclear region in the reactions (K-, pi(+/-)) on Be-9 and in the reaction (K-, n(+)) on He-4 and C-12 can be described without assuming the existence of excited Sigma-hypernuclear s tates. The basis is formed by a simultaneous consideration of the quasifree Sigma production and Sigma-nuclear rescattering (elastic and with Sigma -- > Lambda conversion) with allowance for the interference of the respective amplitudes. To answer completely the question on the nature of the irregula rities in E-exc spectrum, it is proposed to study the picture corresponding to the so-called moving complex singularity of the triangle graph with Sig ma rescattering: the position and the width of the peak in E-exc distributi on should be appreciably changed with momentum transferred from the initial kaon to the final pion. (C) 2000 MAIK "Nauka/lnterperiodica".