Does $J/\psi \rightarrow \pi^{+} \pi^{-}$ fix the Electromagnetic Form Factor $F_{\pi}(t)$ at $t=M_{J/\psi}^2$?

Abstract

We show that the $J/\psi \rightarrow \pi^{+} \pi^{-}$ decay is a reliable source of information for the electromagnetic form factor of the pion at $t=M_{J/\psi}^2=9.6 {\rm GeV}^2$ by using general arguments to estimate, or rather, put upper bounds on, the background processes that could spoil this extraction. We briefly comment on the significance of the resulting $F_{\pi}(M_{J/\psi}^2)$.