发表机构
Institute of Nuclear Physics Polish Academy of Sciences; Institute of Physics, Faculty of Exact and Technical Sciences, University of Rzeszów（波兰科学院核物理研究所; 热舒夫大学精确与技术科学学院物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文研究e+e-碰撞中D Dbar对产生机制，发现D0 Dbar0道连续谱贡献大，Belle和BaBar观测到的3.8 GeV宽峰源于连续谱而非chi_c0(3860)共振，并给出chi_c2(3930)衰变分支比及Belle II和LHC预言。
AI 中文摘要
我们讨论了在 $e^+ e^-$ 碰撞中 $D \bar{D}$ 对产生的机制。我们考虑了具有 $t/u$ 道 $D^*$ 矢量介子交换的 $D^0 {\bar D}^0$ 连续谱机制，其中 $D^* D \gamma$ 耦合常数由 $D^* \to D \gamma$ 衰变导出。对于 $D^+ D^-$ 道，我们主要考虑 $D^{\pm}$ 交换。我们发现 $D^0 {\bar D}^0$ 道具有相对较大的连续谱贡献，而 $D^+ D^-$ 道的贡献显著较小，由此得出结论：Belle 和 BaBar 合作组观测到的 $M_{D^0 {\bar D}^0} = 3.8$ GeV 处的宽峰源于连续谱，而非对应于宽的 $\chi_{c0}(3860)$ 共振。我们还研究了 $D \bar{D}$ 对的共振产生，包括 $\chi_{c0}(3860)$ 和 $\chi_{c2}(3930)$。$\chi_{c2}(3930)$ 介子是第一激发 $P$ 波粲偶素态 $\chi_{c2}(2P)$ 的良好候选者。该共振可以衰变到两个 $D \bar{D}$ 道；然而，其分支比目前尚不十分清楚。将我们的模型结果与 $\Gamma(\chi_{c2}(2P) \to \gamma \gamma) = 0.544$ keV（对应于 Buchmüller-Tye 势）和 BaBar 数据进行比较，我们得到 $B(\chi_{c2}(3930) \to D \bar{D}) = 0.58 \pm 0.13$。我们给出了 Belle II 运动学下几个变量的微分分布结果。最后，我们简要提及了在 LHC 上低不变质量（$M_{D \bar{D}} < 4.3$ GeV）的超外围重离子反应 $Pb Pb \to Pb Pb D \bar{D}$ 的预言。
英文摘要
We discuss mechanisms of $D \bar{D}$ pair production in $e^+ e^-$ collisions. We consider the $D^0 {\bar D}^0$-continuum mechanism with the $t/u$-channel $D^*$ vector-meson exchanges, where the $D^* D γ$ coupling constants are derived from the $D^* \to D γ$ decays. For the $D^+ D^-$ channel, we consider mainly the $D^{\pm}$ exchanges. We find a relatively large continuum contribution for the $D^0 {\bar D}^0$ channel and a significantly smaller one for $D^+ D^-$, concluding that the broad bump at $M_{D^0 {\bar D}^0} = 3.8$ GeV observed by the Belle and BaBar Collaborations has a continuum origin rather than corresponding to the broad $χ_{c0}(3860)$ resonance. We also investigate the resonant production of $D \bar{D}$ pairs, including $χ_{c0}(3860)$ and $χ_{c2}(3930)$. The $χ_{c2}(3930)$ meson is a good candidate for the first excited $P$-wave charmonium $χ_{c2}(2P)$ state. This resonance can decay into both $D \bar{D}$ channels; however, its branching fractions are not well known at present. Comparing our model result with $Γ(χ_{c2}(2P) \to γγ) = 0.544$ keV (corresponding to the Buchmüller-Tye potential) to the BaBar data, we find $B(χ_{c2}(3930) \to D \bar{D}) = 0.58 \pm 0.13$. We present results for differential distributions in several variables for Belle II kinematics. Finally, we shortly mention predictions for the ultraperipheral heavy-ion reaction $Pb Pb \to Pb Pb D \bar{D}$ for low invariant mass ($M_{D \bar{D}} < 4.3$ GeV) at the LHC.
Comments9 pages, 5 figures. Proceedings of the 18th International Workshop on Meson Physics (MESON2026), Kraków, Poland, 2026 June 25-30
