In the heavy quark limit, properties of heavy mesons and doubly heavy baryons are related by heavy quark-diquark symmetry. This problem is reanalyzed in the framework of Non-Relativistic QCD (NRQCD). We introduce a novel method for deriving Potential NRQCD (pNRQCD) Lagrangians for composite fields from vNRQCD, which contains quarks and antiquarks as explicit degrees of freedom and maintains manifest power counting in the velocity via a label formalism. A Hubbard-Stratonovich transformation is used to eliminate four quark interactions in vNRQCD and then quarks and antiquarks are integrated out to get effective Lagrangians for composite fields. This method is used to rederive Lagrangians for the Q\bar Q and QQ sectors of pNRQCD and give a correct derivation of the O(1/m_Q) prediction for the hyperfine splitting of doubly heavy baryons.
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机译：在重夸克极限中，重介子和双重质重子的性质与重夸克-双夸克的对称性有关。在非相对论QCD（NRQCD）框架中重新分析了此问题。我们介绍了一种从vNRQCD导出复合域的潜在NRQCD（pNRQCD）拉格朗日算子的新方法，该方法包含夸克和反夸克作为明确的自由度，并通过标签形式主义保持速度中明显的幂计数。使用Hubbard-Stratonovich转换消除vNRQCD中的四个夸克相互作用，然后将夸克和反夸克集成在一起，以获得有效的拉格朗日算子用于复合场。此方法用于对pNRQCD的Q \ bar Q和QQ扇区重新分配拉格朗日数，并给出对双重质重子超精细分裂的O（1 / m_Q）预测的正确推导。
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