Test of final state approximations using threshold pp→ppπ0

Abstract

The Watson-Migdal approximation scheme to take into account final state interactions is shown to give the actual threshold momentum dependence of the reaction pp → ppπ 0 . However, by an explicit plane wave replacement of the final state wave function it is stressed that not too much physical significance should be given to the proportionality coefficient extracted using this procedure. The plane wave approximation is not physically reliable even after introducing the Watson-Migdal or a more sophisticated final state interaction factor, since direct production (impulse term) is missed. Also with short range interactions there can be discrepancies of a factor two.

Baryon-baryon and baryon-antibaryon interaction amplitudes in the spin-momentum operator expansion method

“…The data provide stringent information on nucleon-nucleon-meson vertices and on the formation of baryon resonances. Selected papers can be found in [117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143].…”

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

“…Recently, some aspects of FSI effects in the reaction NN → NNx were investigated by Hanhart and Nakayama [7] and Niskanen [8]. In particular, these authors pointed out that the evaluation of the total reaction amplitude by just multiplying the production amplitude by the on-shell NN T -matrix is not acceptable for obtaining quantitative predictions.…”

EXPERIMENTAL STUDY OF THE Η-Meson INTERACTION WITH TWO NUCLEONS

“…The solid lines depict calculations where only the proton-proton FSI was taken into account, whereas the dashed lines present results where the overall enhancement was factorized into the corresponding pair interactions of the ppη system. In the left panel the enhancement factor accounting for the proton-proton FSI has been calculated as a square of the on-shell proton-proton scattering amplitude derived according to the modified Cini-Fubini-Stanghellini formula including Wong-Noyes Coulomb corrections [8,10,11], whereas in the right panel the inverse of the Jost function presented in references [9,12] was used. Though the simple phenomenological treatment -based on the factorization of the production amplitude into the constant primary production and the on-shell incoherent pairwise interaction among the exit particles -works astonishingly well in case of the total cross section energy dependence [8], it fails completely in the description of the differential cross section as can be inferred from figure 3(left).…”