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

TL;DR

This paper uses an effective field theory to analyze the unusual lineshape of the $e^+e^- o Dar D$ cross section near the $ ext{psi}(3770)$ resonance, accounting for final-state interactions and nonresonance background effects.

Contribution

It introduces a novel effective field theory approach to model low-energy $Dar D$ interactions and explains the anomalous lineshape observed experimentally.

Findings

The effective field theory successfully describes the observed lineshape.

Final-state interactions significantly influence the $Dar D$ cross section.

Nonresonance background from $ ext{psi}(2S)$ dominates near threshold.

Abstract

We study the anomalous cross-section lineshape of $e^+e^-\rightarrow D\bar D$ 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.