Field and phenomenological description of absorption of particles

The complicated processes in the medium (decays, reactions and $n\bar{n}$ conversion) involving final state absorption are considered. The calculations in the framework of field and phenomenological approaches are compared. The reasons for disagreement are studied. The field approach can tend to increase of total process probability as well as probability of channel corresponding to absorption, in comparison with phenomenological model.Comment: 5 pages, 1 fige

On the multistep processes in the nuclei

The intermediate-state interaction and structure of amplitudes of complicated processes in medium (decays, reactions and the $n\bar{n}$ transitions) are studied. It is proposed to use the branching ratio of channels of free-space hadron-nucleon interaction as a test in the construction and verification of the models. The corresponding formulas for the processes in the medium are obtained. The connection between particle self-energy and amplitudes of subprocesses are analyzed as well.Comment: 5 page

Absorption in the final state in reactions and decays in the medium

The role of strong absorption of particles in intermidiate and final states has been considered. The range of applicability of phenomenological model of absorption has been studied. This model is nonuniversal. Its applicability depends on the type of interaction Hamiltonian and matrix element used. We also demonstrate that the violation of the unitarity condition can produce a qualitative error in the results. The absorption (decay) in the final state does not tend to suppress the total process probability as well as the probability of the channel corresponding to absorption. This is true for the reactions, decays and $n\bar{n}$ conversion in the medium