Role of tensor meson pole and Δ exchange diagrams in pp̄→π⁺π^-

The N̄N→ππ annihilation reaction is investigated in a model with both baryon-exchange diagrams and meson-pole diagrams. The main features of the observed differential cross sections for p̄p→π+π- from 360 to 1190 MeV/c are well understood in this model. The backward enhancement of the differential cross section is mainly due to the NΔπ tensor coupling while the process p̄p→f2→π+π- contributes to the bump structure around 100° developing for Plab>680 MeV/c. This hints at nontrivial quark spin contributions beyond the 3P0 model (which favored S and P waves) and hints at a large gluonic component in tensor mesons with masses between 1.27 and 2.2 GeV.