%0 Journal Article
%A Holz, Simon
%A Hanhart, Christoph
%A Hoferichter, Martin
%A Kubis, Bastian
%T A dispersive analysis of ${\eta '\rightarrow \pi ^+\pi ^-\gamma }$ and ${\eta '\rightarrow \ell ^+\ell ^-\gamma }$
%J The European physical journal / C
%V 82
%N 5
%@ 1434-6044
%C Heidelberg
%I Springer
%M FZJ-2022-02163
%P 434
%D 2022
%X We present a dispersive representation of the η′ transition form factor that allows one to account, in a consistent way, for the effects of ρ–ω mixing in both the isoscalar and the isovector contributions. Using this formalism, we analyze recent data on η′→π+π−γ to constrain the isovector part of the form factor, individually and in combination with data for the pion vector form factor, which suggests a tension in the ρ–ω mixing parameter. As a first application, we use our results, in combination with the most recent input for the isoscalar part of the form factor, to predict the corresponding spectrum of η′→ℓ+ℓ−γ, in particular we find the slope parameter bη′=1.455(24)GeV−2. With forthcoming data on the latter process, our results establish the necessary framework to improve the evaluation of the η′-pole contribution to the anomalous magnetic moment of the muon using experimental input from both η′ decay channels.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ 35578684
%U <Go to ISI:>//WOS:000794907700004
%R 10.1140/epjc/s10052-022-10247-7
%U https://juser.fz-juelich.de/record/907692