We present an effective field theory for doubly heavy baryons that goes beyond the compact heavy diquark approximation. The heavy-quark distance $r$ is only restricted to $m_Q\gg 1/r \gg E_{bin}$, where $m_Q$ is the mass of the heavy quark and $E_{bin}$ the typical binding energy. This means that the size of the heavy diquark can be as large as the typical size of a light hadron. We start from Non-Relativistic QCD, and build the effective field theory at next-to-leading in the $1/m_Q$ expansion. At leading order the effective field theory reduces to the Born-Oppenheimer approximation. The BO potentials are obtained from available lattice QCD data. The spectrum for double charm baryons below threshold is compatible with most of the lattice QCD results. We present for the first time the full spin averaged double bottom baryon spectrum below threshold based on QCD. We also present model-independent formulas for the spin splittings.

中文翻译：

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强耦合下双重重子的有效场论

我们提出了一个有效的双重重子场理论，它超越了紧凑的重迪夸克近似。重夸克距离 $r$ 仅限于 $m_Q\gg 1/r \gg E_{bin}$，其中 $m_Q$ 是重夸克的质量，$E_{bin}$ 是典型的结合能。这意味着重迪夸克的大小可以与轻强子的典型大小一样大。我们从非相对论 QCD 开始，并在 $1/m_Q$ 扩展中以次领先建立有效场论。在领先阶有效场论简化为 Born-Oppenheimer 近似。BO 电位是从可用的晶格 QCD 数据中获得的。低于阈值的双粲重子的光谱与大多数晶格 QCD 结果兼容。我们首次提出了基于 QCD 的低于阈值的全自旋平均双底重子谱。我们还提出了与模型无关的自旋分裂公式。