PT Journal
AU Holz, S
   Plenter, J
   Xiao, CW
   Dato, T
   Hanhart, C
   Kubis, B
   Meissner, UG
   Wirzba, A
TI Towards an improved understanding of eta -> gamma*gamma *
SO European Physical Journal C
JI Eur. Phys. J. C
PY 2021
BP 1002
EP 15pp
VL 81
IS 11
DI 10.1140/epjc/s10052-021-09661-0
LA English
AB We argue that high-quality data on the reaction e(+)e(-) -> pi(+) pi(-) eta will allow one to determine the doubly-virtual form factor eta -> gamma*gamma* in a model-independent way with controlled accuracy. This is an important step towards a reliable evaluation of the hadronic light-by-light scattering contribution to the anomalous magnetic moment of themuon. When analyzing the existing data for e(+) e(-) -> pi(+) pi(-) eta for total energies squared k(2) > 1GeV(2), we demonstrate that the effect of the a(2) meson provides a natural breaking mechanism for the commonly employed factorization ansatz in the doubly-virtual form factor F-eta gamma*gamma* (q(2), k(2)). However, better data are needed to draw firm conclusions.
ER