Comparing antithetic trends of data for the pion-photon transition form factor

Abstract

We perform a comparative theoretical study of the data at spacelike momentum transfer for the ${\gamma }^{\ast }\gamma \to {\pi }^0$ transition form factor, just reported by the Belle Collaboration, vs. those published before by BaBar, also including the older CLEO and CELLO data. Various implications for the structure of the ${\pi }^0$ distribution amplitude vis-à-vis those data are discussed and the existing theoretical predictions are classified into three distinct categories. We argue that the actual bifurcation of the data with antithetic trends is artificial and reason that the Belle data are the better option.

Comments: v1: 5 pages, 1 table, 2 figures. v2: 1 figure added and discussed in text; references regrouped, added and/or updated. v3: matches version to be published in PRD