title: Dispersive analysis of the pion transition form factor.
abstract: 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 [Formula: see text] cross section, generalizing previous studies on [Formula: see text] decays and [Formula: see text] scattering, and verify our result by comparing to [Formula: see text] data. We perform the analytic continuation to the space-like region, predicting the poorly-constrained space-like transition form factor below [Formula: see text], and extract the slope of the form factor at vanishing momentum transfer [Formula: see text]. 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.
authors.affiliation: Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany ; ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany ; Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Hoferichter
authors.affiliation: Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, 53115 Bonn, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Kubis
authors.affiliation: Institutionen för fysik och astronomi, Uppsala Universitet, Box 516, 75120 Uppsala, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Leupold
authors.affiliation: Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, 53115 Bonn, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Niecknig
authors.affiliation: Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, 53115 Bonn, Germany.
authors.forename: S P
authors.initials: SP
authors.lastname: Schneider