Study of the anomalous cross-section lineshape of e+e−→DD¯ at ψ(3770) with an effective field theory

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