The transition form factor from space- and time-like experimental data

R. Escribano; P. Masjuan; P. Sanchez-Puertas

doi:10.1140/epjc/s10052-015-3642-z

EPJ

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2023 Impact factor 4.2

Particles and Fields

Open Access

Eur. Phys. J. C (2015) 75: 414
https://doi.org/10.1140/epjc/s10052-015-3642-z

Regular Article - Theoretical Physics

The $\eta$ transition form factor from space- and time-like experimental data

R. Escribano¹, P. Masjuan²^* and P. Sanchez-Puertas²

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

Abstract

The $\eta$ 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 $\eta \rightarrow e^+e^-\gamma$ 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 $\eta$ – $\eta ^\prime$ system, together with the role played by renormalization dependent effects, and on the determination of the $VP\gamma$ couplings from $V\rightarrow P\gamma$ and $P\rightarrow V\gamma$ radiative decays is also discussed.