The pi pi Phase Shifts from psi' to J/psi pi^+ pi^- Decays

Abstract

The ${\psi }^{\prime }\to J/\psi {\pi }^{+}{\pi }^{-}$ decay process provides a new way to extract the $\pi \pi$ $S$ wave phase shifts up to $0.59GeV$. In this paper we derive the formulae for extracting the $\pi \pi$ $S$ wave phase shifts from the invariant mass spectrum of $\pi \pi$ in the ${\psi }^{\prime }\to J/\psi {\pi }^{+}{\pi }^{-}$ decay.

Comments: 7 pages, 1 figure. A misprint in Eq.(13) corrected