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arXiv 0908.1758hep-ph
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光锥下全QCD的半轻子$Λ_{b,c}$到核子跃迁

Semileptonic $Λ_{b,c}$ to Nucleon Transitions in Full QCD at Light Cone

K. Azizi, M. Bayar, Y. Sarac, H. Sundu

摘要:

利用光锥QCD求和定则方法,在全理论下研究了树能级半轻子$Λ_{b}\to plν$和$Λ_{c}\to nlν$跃迁。自旋为1/2的$Λ_{Q}$重子具有$Q=b$或$c$,我们用它的内插流的最一般形式来考虑.初始流和跃迁流的时间序积被展开成不同扭曲度的核子分布振幅。考虑到核子波函数的两组相互独立的输入参数,即QCD求和规则和格点QCD参数,计算了相应的形状因子及其重夸克有效理论极限,并与已有的其他方法的预言进行了比较.结果表明,对于格点输入参数和b情形,我们的结果完全满足重夸克对称性关系,而对于粲情形和QCD求和规则输入参数,我们的结果满足最大的破坏.利用得到的形状因子计算了全理论和重夸克有效理论下的跃迁率。在不同的内插电流和$Λ_{b}$分布振幅下,将$Λ_{b}\to plν$的衰变率结果与其它唯象方法或重夸克有效理论中相同方法的结果进行了比较。

英文摘要:

The tree level semileptonic $Λ_{b}\to plν$ and $Λ_{c}\to nlν$ transitions are investigated using the light cone QCD sum rules approach in full theory. The spin--1/2, $Λ_{Q}$ baryon with $Q=b$ or $c$, is considered by the most general form of its interpolating current. The time ordering product of the initial and transition currents is expanded in terms of the nucleon distribution amplitudes with different twists. Considering two sets of independent input parameters entering to the nucleon wave functions, namely, QCD sum rules and Lattice QCD parameters, the related form factors and their heavy quark effective theory limits are calculated and compared with the existing predictions of other approaches. It is shown that our results satisfy the heavy quark symmetry relations for lattice input parameters and b case exactly and the maximum violation is for charm case and QCD sum rules input parameters. The obtained form factors are used to compute the transition rates both in full theory and heavy quark effective theory. A comparison of the results on decay rate of $Λ_{b}\to plν$ with those predicted by other phenomenological methods or the same method in heavy quark effective theory with different interpolating current and distribution amplitudes of the $Λ_{b}$ is also presented.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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