Information on the structure of the rho meson from the pion form-factor

Abstract

The electromagnetic pion form-factor is calculated in a Bethe-Salpeter approach which accounts for pion rescattering. In the scattering kernel the pion-pion contact interaction from lowest-order chiral perturbation theory is considered together with an optional vector meson in the s-channel. Correspondingly the virtual photon couples to a two-pion state and optionally to the vector meson. It is shown that for reasonable ranges of input parameters the experimentally observed pion form-factor cannot be described by the iterated pion-pion contact interaction alone, i.e. without an elementary vector meson. The inclusion of an elementary vector meson allows for an excellent description. This completes a recent study (``Information on the structure of the a_1 from tau decay'') where it has been shown that the a_1 meson can be well understood as a rescattering process of rho meson and pion. Here it is demonstrated that within the same formalism the rho meson cannot be understood as a pion-pion rescattering process. This suggests that the chiral partners a_1 and rho are not only different in mass, but also different in nature.

12 pages

References in corpus (6)

• Origin of resonances in the chiral unitary approach
• On the radiative decays of light vector and axial-vector mesons
• Quark mass dependence of the pion vector form factor
• Information on the structure of the a1 from tau decay
• Hadronic three-body decays of light vector mesons
• Tau decay and the structure of the a1

Cited by in corpus (5)

• Chiral QCD sum rules for open charm mesons
• Reactions with pions and vector mesons in the sector of odd intrinsic parity
• Vector form factor of the pion in chiral effective field theory
• Renormalisation of the low-energy constants of chiral perturbation theory from loops with dynamical vector mesons
• Towards an effective field theory for vector mesons