On the treatment of NN interaction effects in meson production in NN collisions

Abstract

We clarify under what circumstances the nucleon-nucleon final state interaction fixes the energy dependence of the total cross-section for the reaction N N → N N x close to production threshold, where x can be any meson whose interaction with the nucleon is not too strong. We strongly criticize the procedure used recently by several authors to include the final state interaction in the reactions under discussion. In addition, we give a formula that allows one to estimate the effect of the initial state interaction for the production of heavy mesons. In the above equation q ′ is the momentum of the outgoing meson and A(E, p ′ ) is the NN → NNx transition amplitude, which, for future convenience, is

Few-Body Aspects of the Near Threshold Pseudoscalar Meson Production

“…Close-to-threshold the production cross section of pseudoscalar mesons is reduced by the initial state interaction (ISI) of the colliding nucleons by a factor of about 4 [10,11] and it is enhanced by the final state interaction (FSI) by more than an order of magnitude [2]. The reduction of the cross section due to the ISI strongly depends on the meson mass and therefore as it was introduced in reference [12], the strength of the production dynamics is at best expressed as the total cross section normalized to the ISI factor.…”

Near-thresholdωandφmeson productions inppcollisions

“…As discussed in Ref. [40], this is a reasonable approximation to the full NN ISI. In this approximation the basic effect of the NN ISI is to reduce the magnitude of the meson production cross section [39,44].…”

“…In the present work we follow Ref. [40], and make the on-shell approximation to evaluate the ISI contribution, which was also applied in the study of the NN → NNη reaction [39]. This amounts to keeping only the δ−function part of the Green function G i in evaluating the loop integral involving iG…”

“…The ISI is implemented in the on-shell approximation [2,30,39,40], while the FSI is generated using the Bonn NN potential model [41]. The finite width of the ω, which is very important near threshold energies, is also included.…”

Reexamination of the role of theΔ*resonances in thepp→nK+Σ+reaction

“…In our model, the initial state interaction (ISI) is not considered because it is difficult to treat the ISI unambiguously due to the lack of the accurate NN interaction model at such high incident beam energies. Hanhart and Nakayama [43] claims that the ISI has practically little influence on the energy dependence of the meson production cross section of nucleon-nucleon collisions close to threshold, and the reduction factor to the cross section can be roughly estimated by the N N phase shifts and inelasticities. In our paper, we do not consider this reduction factor because this estimation is rough so it would cause uncertainty in the model.…”