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

Abstract

We show that the $J/ψ\rightarrow π^{+} π^{-}$ decay is a reliable source of information for the electromagnetic form factor of the pion at $t=M_{J/ψ}^2=9.6 {\rm GeV}^2$ 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 $F_π(M_{J/ψ}^2)$.