Abstract
The excitation curve of annihilation into four charged pions in the region is calculated using three existing models with mesons and pions in intermediate states supplemented by Feynman diagrams with the intermediate states. A two-term phenomenological Lagrangian of the interaction is used. The mixing angle is determined by fitting the cross section data of the Novosibirsk CMD-2 Collaboration and also its combination with the low-energy part of the BABAR Collaboration data. It is shown that the inclusion of the intermediate states succeeds in obtaining a good agreement with the data on both cross section and the decay width. When moving to energies above 1 GeV, the and resonances are taken into account to get excellent agreement with the BABAR data over the full energy range up to 4.5 GeV.
- Received 27 January 2006
DOI:https://doi.org/10.1103/PhysRevD.76.094030
©2007 American Physical Society