On August 21, 2024, the BESIII collaboration has published an article entitled “Precise Measurement of Born Cross Sections for e-e+→ DDbar at √s=3.80-4.95 GeV” in Physical Review Letters [Phys. Rev. Lett. 133 (2024) 081901], reporting groundbreaking measurements of Born cross sections for the e+e-→ D0D0bar and D+D-bar reactions at 150 center-of-mass energies between 3.80 and 4.95 GeV with unprecedented precision.

The study of hadron structure has always been a frontier and hot field in particle physics. The search for new potential hadron structures is crucial for validating the accuracy of QCD theory and promoting the development of strong interaction theory. Charm quarkonium is located in the transition region between non-pQCD and pQCD. Investigating the decay of charmonium(-like) or searching for new candidates of charmonium(-like) states is a significant way to deepen our understanding of QCD. In recent years, with the improvement of experimental research capabilities, a series of vector charmonium-like states such as Y(4230), Y(4360), Y(4660), etc. have been discovered in experimental studies on electron-positron pairs annihilating into hidden-charm final states. Despite various theoretical models have been proposed, including hadron molecular states, hybrid states, tetraquark states, etc., attempting to solve the nature of these states, there is still no universally theory that can fully account for experimental measurements. Particularly, the experimental measurement on electron-positron pairs annihilating into open-charm final states which remains scarce would provide an important input to probe the nature of vector charmonium(-like) states.

The BESIII experiment, which is a spectrometer operating in the tau-charm physical region, has accumulated the world's largest data sample in this energy region. Using a total of 20/fb e+e- scan data sample between 3.80 and 4.95 GeV collected by BESIII detector, the Born cross sections of e+e-→ D0D0bar and D+D-bar have been measured with unprecedented precision at 150 center-of-masses energies. Many clear peaks in the line shape of the cross sections of e+e- → D0D0bar and D+D-bar around the mass range of ψ(4040), ψ(4160), Y(4230), and ψ(4415), etc. are seen. These results offer essential experimental insights into the nature of the vector-charmonium(-like) states above open charm region and have a significant impact on future research.

PRL: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.133.081901
arXiv: https://arxiv.org/abs/2402.03829