https://doi.org/10.1140/epjc/s10052-014-3180-0
Regular Article - Theoretical Physics
Dispersive analysis of the pion transition form factor
1
Institut für Kernphysik, Technische Universität Darmstadt, 64289, Darmstadt, Germany
2
ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291, Darmstadt, Germany
3
Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
4
Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, 53115, Bonn, Germany
5
Institutionen för fysik och astronomi, Uppsala Universitet, Box 516, 75120, Uppsala, Sweden
* e-mail: hoferichter@theorie.ikp.physik.tu-darmstadt.de
Received:
19
October
2014
Accepted:
11
November
2014
Published online:
27
November
2014
We analyze the pion transition form factor using dispersion theory. We calculate the singly-virtual form factor in the time-like region based on data for the 
cross section, generalizing previous studies on 
decays and 
scattering, and verify our result by comparing to 
data. We perform the analytic continuation to the space-like region, predicting the poorly-constrained space-like transition form factor below 
, and extract the slope of the form factor at vanishing momentum transfer 
. We derive the dispersive formalism necessary for the extension of these results to the doubly-virtual case, as required for the pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon.
© SIF and Springer-Verlag Berlin Heidelberg, 2014
