Anomalous Line-Shape of Cross Sections for $e^+e^- \to {\rm Hadrons}$ in the Center-of-Mass Energy Region between 3.650 and 3.872 GeV

TL;DR

The paper reports an anomalous line-shape in the cross sections for $e^+e^- o$ hadrons between 3.700 and 3.872 GeV, suggesting possible new structures or effects beyond the known $ ext{psi}(3770)$ resonance.

Contribution

It provides a detailed re-analysis of the cross-section data revealing inconsistencies with a single resonance model, indicating potential new physics or structures.

Findings

Anomalous line-shape observed in the energy region 3.700-3.872 GeV.

Inconsistency with a single $ ext{psi}(3770)$ resonance explanation.

Possible new structures near 3.764 GeV and 3.779 GeV.

Abstract

We observe an obvious anomalous line-shape of the $e^+e^- \to {\rm hadrons}$ total cross sections in the energy region between 3.700 and 3.872 GeV from the data samples taken with the BES-II detector at the BEPC Collider. Re-analysis of the data shows that it is inconsistent with the explanation for only one simple $\psi(3770)$ resonance with a statistical significance of $7\sigma$. The anomalous line-shape may be explained by two possible enhancements of the inclusive hadron production near the center-of-mass energies of 3.764 GeV and 3.779 GeV, indicating that either there is likely a new structure in addition to the $\psi(3770)$ resonance around 3.773 GeV, or there are some physics effects reflecting the $D\bar D$ production dynamics.