Rho-omega mixing and the pion form factor in the timelike region

Abstract

We determine the magnitude, phase, and s-dependence of ρ-ω "mixing" in the pion form factor in the time-like region through fits to e + e − → π + π − data. The associated systematic errors in these quantities, arising from the functional form used to fit the ρ resonance, are small. The systematic errors in the ρ mass and width, however, are larger than previously estimated.

Vector meson dominance and ρ-ω mixing

“…It is the latter value which was shown in sections 2 and 3 to be consistent with the universality discussed there. The most recent extraction of a ρ • − ω mixing parameter from the data eschews such a separation into a contact ω → π + π − and mixing ω → ρ → 2π term on the grounds that it is model dependent [33,34]. As we have seen, a significant contact G-parity violating ω → 2π coupling would increase in magnitude the value of ρ • |H em |ω to such an extent that it would not be consistent with the off-diagonal ρ • − ω tadpole scales (6) and (7), nor with the diagonal tadpole scales in (9) and (10), nor with the diagonal tadpole scales obtained from the baryon mass differences [15].…”

The pion form factor within the hidden local symmetry model

“…The ρ mass, as defined by the real part of the propagator M ρ , is highly model dependent [35]. The complex pole, however, is a true invariant, as has been shown for several models [31].…”

Spacelike and timelike pion electromagnetic form factor and Fock state components within the light-front dynamics

“…It should be pointed out that current analyses of the experimental data in the TL region are carried on by using large sets of parameters (see e.g. [39,40]). …”