Study of the anomalous cross-section lineshape of e^+e^-\to D\bar D at \psi(3770) with an effective field theory

Abstract

We study the anomalous cross-section lineshape of $e^{+}{e}^{-}\to D\bar{D}$ with an effective field theory. Near the threshold, most of the $D\bar{D}$ pairs are from the decay of $\psi (3770)$. Taking into account the fact that the nonresonance background is dominated by the $\psi (2S)$ transition, the produced $D\bar{D}$ pair can undergo final-state interactions before the pair is detected. We propose an effective field theory for the low-energy $D\bar{D}$ interactions to describe these final-state interactions and find that the anomalous lineshape of the $D\bar{D}$ cross section observed by the BESII collaboration can be well described.

Comments: 10 pages,6 figures, redo the calculation with PDS scheme and more discussions added, accepted by Phys.Lett.B