ηandη′transition form factors from rational approximants

Abstract

The η and η 0 transition form factors in the spacelike region are analyzed at low and intermediate energies in a model-independent way through the use of rational approximants. The slope and curvature parameters of the form factors as well as their values at zero and infinity are extracted from experimental data. The impact of these results on the mixing parameters of the η-η 0 system and the pseudoscalar-exchange contributions to the hadronic light-by-light scattering part of the anomalous magnetic moment a μ are also discussed.

ηandη′Physics at MAMI

“…The model- independent method using Padé-approximants that was developed for the π 0 TFF in ref. [37] uses spacelike data to provide a model-independent prediction for the timelike TFF [38]. This calculation almost perfectly agrees with the fit.…”

“…Data are compared in (a) to the first A2 determination [30] (open circles) and in (b) to the result from the NA60 collaboration [32] (open squares). Theoretical calculations are in (a) from Terschlüsen and Leupold (TL) [33] (dashed-dotted line) and the model independent method based on Padé-approximants [38] (dashed line with error band). In (b) a calculation based on dispersion theory (DT) is shown [39] (dotted line with error band).…”

π0−η−η′mixing in a generalized multiquark interaction scheme

“…Set (a) corresponds to an octet-singlet mixing angle in the scalar sector of θ S ¼ 27.5°, set (b) to θ S ¼ 25°. [62], and compared with the results of other approaches [22] and references therein, [54,80,81], and of Padé approximant method to pseudoscalar transition form factors [82,83], where in the Table IV, ðηÞ and ðη 0 Þ refer to the asymptotes taken for the fits, and the results obtained from BABAR data [84] by the same authors (see discussion in [82] concerning the BABAR "puzzle"). This comparison shows that set (a) yields results quite close to the chiral perturbation analysis of [80] and follows the general trend of the other references in the table, with exception of the sum rules approach of [81], and the fits from [84].…”

Hadron form factors and large-Ncphenomenology

“…Applications to the hadronic density of states, the anomalous magnetic moment of the muon, and the analysis of MiniBooNE data are discussed in Ref. [7][8][9]. …”