Proposal to observe the strong Van der Waals force in e+\bar{e} -> 2 \pi

Abstract

Large discrepancy of the p-wave phase shift data $\delta_{1}(\nu)$ of the $\pi$-$\pi$ scattering from those of the dispersion calculation is pointed out. In order to determine which is correct, the pion form factor $F_{\pi}(\nu)$, which is the second source of information of the phase shift $\delta_{1}(\nu)$, is used. It is found that the phase shift obtained from the dispersion is not compatible with the data of the pion form factor. What is wrong with the dispersion calculation, is considered.