Measurement of the $\eta$ transition form factor through ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}\eta$ decay

BESIII Collaboration, M. Ablikim, M. N. Achasov +678

Based on a sample of $(1.0087\pm 0.0044)\times 10^{10}$ $J/\psi$ events collected at BESIII, the transition form factor of the $\eta$ meson is extracted by analyzing $J/ψ\toγη',~η'\toπ^+π^…