On the migdal-watson approach to FSI effects in meson production in NN collisions

Abstract

The influence of the nucleon-nucleon final state interaction (FSI) on properties of the meson production amplitude near threshold is discussed. For the nucleon-nucleon interaction a simple Yamaguchi potential as well as realistic potential models are considered. It is shown that FSI effects cannot be factorized from the production amplitude. The absolute magnitude of FSI effects depends on the momentum transfer (or on the mass of the produced meson) and hence is not universal. Only in the case of the production of rather heavy mesons like η ′ or φ FSI effects become universal. The Jost function approach to FSI effects is critically examined. : 13.75.-n, 25.10.+s, 25.40.-h 7 PACS

Near threshold enhancement of thepp¯mass spectrum inJ/Ψdecay

“…In case of the N N 1 S 0 partial wave |c| is indeed large, as has been demonstrated in Ref. [44]. In considering the S-wave interaction in the final pp system one should account for the centrifugal barrier between the photon and the pp state given by the factor…”

“…However, the prescription of Watson-Migdal is only valid for interactions that yield a rather large scattering length, like the 1 S 0 N N partial wave where the scattering length a is in the order of 20 fm, and even then only for a relatively small energy range, as was pointed out in several recent papers [42][43][44]. Therefore, in the present case, where the scattering lengths are in the order of 1 fm one should be cautious with the interpretation of results obtained from applying Eq.(5).…”

Reconciling theX(4630)with theY(4660)

“…[23], which was derived using SU(4) flavor-symmetry arguments, and compute the Jost function J (M ) for this interaction. Multiplying the reaction amplitude with the inverse of the latter quantity, also known as enhancement factor, is practically equivalent to a treatment within a distorted-wave Born approximation [24,25]. The width of Y (4660) → Λ + c Λ − c is then given by…”

Production of a0 mesons in pp and pn reactions

“…For this purpose we adopt the FSI model from Ref. [40] based on the (realistic) Paris potential. We use, however, the enhancement factor F N N (q N N ) -as given by this model -only in the region of small relative momenta of the final nucleons q N N ≤ q 0 , where it is larger than 1.…”