The branching ratio omega -> pi(+) pi(-) revisited

We analyze themost recent data for the pion vector form factor in the timelike region, employing a modelindependent approach based on dispersion theory. We confirm earlier observations about the inconsistency of different modern high-precision data sets. Excluding the BaBar data, we find an updated value for the isospin-violating branching ratio B(omega -> pi(+) pi(-)) = (1.46 +/- 0.08) x 10(-2). As a side result, we also extract an improved value for the pion vector or charge radius, root < r(V)(2)> = 0.6603(5)(4) fm, where the first uncertainty is statistical as derived from the fit, while the second estimates the possible size of nonuniversal radiative corrections. In addition, we demonstrate that modern high-quality data for the decay. eta'-> pi(+) pi(-) will allow for an even improved determination of the transition strength omega -> pi(+) pi(-).
Correction in: European Physical Journal C, vol. 78, issue 6, article Number: 450.DOI: 10.1140/epjc/s10052-018-5941-7