https://doi.org/10.1140/epjc/s10052-015-3642-z
Regular Article - Theoretical Physics
The 
transition form factor from space- and time-like experimental data
1
Departament de Física, Grup de Física Teòrica, and Institut de Física d’Altes Energies (IFAE), Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
2
PRISMA Cluster of Excellence, Institut für Kernphysik, Johannes Gutenberg-Universität, 55099, Mainz, Germany
* e-mail: masjuan@kph.uni-mainz.de
Received:
1
June
2015
Accepted:
17
August
2015
Published online:
9
September
2015
The transition form factor is analyzed for the first time in both space- and time-like regions at low and intermediate energies in a model-independent approach through the use of rational approximants. The 
experimental data provided by the A2 Collaboration in the very low-energy region of the dielectron invariant mass distribution allows for the extraction of the most precise up-to-date slope and curvature parameters of the form factors as well as their values at zero and infinity. The impact of these new results on the mixing parameters of the –
system, together with the role played by renormalization dependent effects, and on the determination of the 
couplings from 
and 
radiative decays is also discussed.
© SIF and Springer-Verlag Berlin Heidelberg, 2015
