Dispersive analysis of the pion transition form factor

• 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 e(+) e(-) -> 3 pi cross section, generalizing previous studies on omega, phi -> 3 pi decays and gamma pi -> pi pi scattering, and verify our result by comparing to e(+) e(-) -> pi(0)gamma. data. We perform the analytic continuation to the space-like region, predicting the poorly-constrained space-like transition form factor below 1GeV, and extract the slope of the form factor at vanishing momentum transfer a(pi) = (30.7 +/- 0.6) x10(-3). 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.

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NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

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