$D\bar{D}$ production and their interactions

TL;DR

This paper investigates D and D̄ meson pair interactions and production in electron-positron collisions, using a meson exchange model to analyze scattering phases and explore the possibility of bound states, but finds difficulty explaining certain experimental anomalies.

Contribution

It introduces a meson exchange model with heavy quark effective theory couplings to study D̄D interactions and estimates bounds on potential molecular bound states from experimental data.

Findings

P wave phase shifts extracted from data

Upper limit of the cutoff parameter estimated as 1.7 GeV

Upper bounds on S wave D̄D and B̄B bound state energies

Abstract

S and P wave $D\bar{D}$ scatterings are studied in a meson exchange model with the coupling constants obtained in the heavy quark effective theory. With the extracted P wave phase shifts and the separable potential approximation, we include the $D\bar{D}$ rescattering effect and investigate the production process $e^+e^-\to D\bar{D}$. We find that it is difficult to explain the anomalous line shape observed by the BES collaboration with this mechanism. Combining our model calculation and the experimental measurement, we estimate the upper limit of the nearly universal cutoff parameter to be 1.7 GeV. With this number, the upper limits of the binding energies of the S wave $D\bar{D}$ and $B\bar{B}$ bound states are obtained. Assuming that the S wave and P wave interactions rely on the same cutoff, our study provides a way of extracting the information about S wave molecular bound states from the P wave meson pair production.