Meson-baryon dynamics in the nucleon-antinucleon system. I. The nucleon-antinucleon interaction

The electromagnetic form factors of the proton in the timelike region

“…At higher kinetic energies or, generally, over a larger energy region, the intrinsic energy-and momentum dependence of theNN production mechanism itself may become significant or even dominant and then our assumption that G 0 E and G 0 M are constant is no longer valid. Besides the EFT interaction we consider again the Jülich NN model A(OBE) [21], which has already been used in our earlier study [28].…”

“…Indeed, a few years ago we have studied the energy dependence of the e + e − ↔pp cross section close to threshold, within the Watson-Migdal approach [28]. We could show that the near-threshold enhancement in the e + e − →pp cross section can be explained qualitatively bypp FSI effects in the 3 S 1 partial wave as generated by the Jülich nucleon-antinucleon model [21]. Similar results were also reported by other authors based on somewhat different approaches and employing otherNN interactions [29,30,31,32,33,34,35].…”

“…For the potential V in Eq. (9) we utilize a recently published interaction derived within chiral EFT [37] and fitted to results of a new PWA ofpp scattering data [36], and one of the phenomenologicalNN models constructed by the Jülich group [21]. In the above equations…”

“…However, it was also shown that a conventional but plausible interpretation of the data can be given simply in terms of the final-state interaction (FSI) between the produced proton and antiproton [16,17,18,19,20]. Specifically, calculations of our group, utilizing the Jülich NN model [21,22,23] and performed within the Watson-Migdal approach [24,25], could reproduce the mass dependence of thepp spectrum close to the threshold by the S -wavepp FSI for various decays [16,26,27].…”

“…Based on that work anNN potential has been constructed by us [37], in the framework of chiral effective field theory (EFT), that reproduces the amplitudes determined in the PWA very well up to laboratory energies of T lab ≈ 200 − 250 MeV. This potential will be now employed for the final-state interaction, besides the phenomenologicalNN model of the Jülich group [21] used in our earlier work [28].…”