Abstract
AbstractWe present a dispersive representation of the $$\eta '$$
η
′
transition form factor that allows one to account, in a consistent way, for the effects of $$\rho $$
ρ
–$$\omega $$
ω
mixing in both the isoscalar and the isovector contributions. Using this formalism, we analyze recent data on $$\eta '\rightarrow \pi ^+\pi ^-\gamma $$
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 $$\rho $$
ρ
–$$\omega $$
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 $$\eta '\rightarrow \ell ^+\ell ^-\gamma $$
η
′
→
ℓ
+
ℓ
-
γ
, in particular we find the slope parameter $$b_{\eta '}=1.455(24)\,\text {GeV}^{-2}$$
b
η
′
=
1.455
(
24
)
GeV
-
2
. With forthcoming data on the latter process, our results establish the necessary framework to improve the evaluation of the $$\eta '$$
η
′
-pole contribution to the anomalous magnetic moment of the muon using experimental input from both $$\eta '$$
η
′
decay channels.
Funder
Deutsche Forschungsgemeinschaft
U.S. Department of Energy
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Publisher
Springer Science and Business Media LLC
Subject
Physics and Astronomy (miscellaneous),Engineering (miscellaneous)
Cited by
11 articles.
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