Low-lying Lambda Baryons with spin 1/2 in Two-flavor Lattice QCD
Low-lying Lambda Baryons with spin 1/2 in Two-flavor Lattice QCD
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DOI：
10.1103/physrevd.81.034505
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发表时间：
2009-10
影响因子：
5
通讯作者：
Toru T. Takahashi;M. Oka
中科院分区：
文献类型：
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作者：
Toru T. Takahashi;M. Oka
在全(非猝灭)晶格QCD中分析了自旋为1/2的低位{Lambda}重子。我们从味SU(3)八重子算符和单重子算符构造了2x2交叉相关器，并将它们对角化，以提取每个宇称的两个低能态的信息。采用重整化群改进规范作用和O(A)-改进夸克作用产生的双味CP-PACS规范组态。采用了三种不同的{β}‘S，{β}=1.80，1.95和2.10，其对应的晶格间距分别为a=0.2150，0.1555和0.1076 fm。对于每个截止点，我们使用四个跳跃参数({kappa}{subVal}，{kappa}{subSEA})，它们对应于从500 MeV到1.1GeV的介子质量。结果表明，在1.6GeV附近有两个近乎简并的负宇称{Lambda}态，而没有观察到低至{Lambda}(1405)的态。通过对每个态的风味成分的分解，我们发现最低的(第一激发)负宇称态是由风味单态(风味八重态)组成的。我们还讨论了每个态的介子-重子分量，这在{Lambda}(1405)的多夸克照片中引起了相当大的关注。
Low-lying {Lambda} baryons with spin 1/2 are analyzed in full (unquenched) lattice QCD. We construct 2x2 cross correlators from flavor SU(3) octet and singlet baryon operators, and diagonalize them so as to extract information of two low-lying states for each parity. The two-flavor CP-PACS gauge configurations are used, which are generated in the renormalization-group improved gauge action and the O(a)-improved quark action. Three different {beta}'s, {beta}=1.80, 1.95, and 2.10, are employed, whose corresponding lattice spacings are a=0.2150, 0.1555, and 0.1076 fm. For each cutoff, we use four hopping parameters, ({kappa}{sub val},{kappa}{sub sea}), which correspond to the pion masses ranging about from 500 MeV to 1.1 GeV. Results indicate that there are two negative-parity {Lambda} states nearly degenerate at around 1.6 GeV, while no state as low as {Lambda}(1405) is observed. By decomposing the flavor components of each state, we find that the lowest (1st-excited) negative-parity state is dominated by flavor-singlet (flavor-octet) component. We also discuss meson-baryon components of each state, which has drawn considerable attention in the context of multiquark pictures of {Lambda}(1405).