On the production mechanism of Σ-hypernuclear systems in A(K −, π±) reactions

Abstract

It is shown that the new data on the excitation energy E exc spectrum of the residual nuclear system in the Σ-hypernuclear region in the reactions (K −, π±) on 9Be and in the reaction (K −, π+) on 4He and 12C can be described without assuming the existence of excited Σ-hypernuclear states. The basis is formed by a simultaneous consideration of the quasifree Σ production and Σ-nuclear rescattering (elastic and with Σ → Λ conversion) with allowance for the interference of the respective amplitudes. To answer completely the question on the nature of the irregularities in E exc spectrum, it is proposed to study the picture corresponding to the so-called moving complex singularity of the triangle graph with Σ rescattering: the position and the width of the peak in E exc distribution should be appreciably changed with momentum transferred from the initial kaon to the final pion.