Electron-positron annihilation into four charged pions and the a_1-rho-pi Lagrangian

Abstract

The excitation curve of e+e- annihilation into four charged pions in the rho(770) region is calculated using three existing models with rho mesons and pions in intermediate states supplemented by Feynman diagrams with the a_1(1260)pi intermediate states. A two-term phenomenological Lagrangian of the a_1-rho-pi interaction is used. The mixing angle is determined by fitting the e+e- --> pi+pi-pi+pi- 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 a_1-pi intermediate states succeeds in obtaining a good agreement with the data on both cross section and the rho^0 --> pi+pi-pi+pi- decay width. When moving to energies above 1 GeV, the rho(1450) and rho(1700) resonances are taken into account to get excellent agreement with the BaBar data over the full energy range up to 4.5 GeV.

15 pages, 6 figures. Largely extended. The title changed to reflect new content

References in corpus (7)

• The Cosmological Parameters 2006
• Big-Bang nucleosynthesis (Particle Data Group mini-review)
• First Measurement of the rho Spectral Function in High-Energy Nuclear Collisions
• The $\epem\toπ^+π^-π^+π^-$, $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}$, and $K^{+}{K}^{-}{K}^{+}{K}^{-}$ Cross Sections at Center-of-Mass Energies 0.5--4.5 \gev Measured with Initial-State Radiation
• Masses and couplings of vector mesons from the pion electromagnetic, weak, and πγtransition form factors
• Role of a_1(1260) resonance in multipion decays of light vector mesons
• Photon production in relativistic nuclear collisions at SPS and RHIC energies

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