arXiv 0907.40082009-07-23hep-ph

从QCD光锥求和规则得到的$Λ_b \to p, Λ$跃迁形状因子

$Λ_b \to p, Λ$ transition form factors from QCD light-cone sum rules

Yu-Ming Wang, Yue-Long Shen, Cai-Dian Lu

备注：: 18 pages, 5 figures
发表信息：: Phys.Rev.D80:074012,2009
DOI：: 10.1103/PhysRevD.80.074012

摘要：

从$Λ_b$重子分布振幅扭曲展开的关联函数出发，导出了$Λ_b \to p, Λ$跃迁形状因子的光锥求和规则.在QCD理论约束下的$Λ_b$三夸克分布振幅模型中，计算了小动量转移时的形状因子，并与传统的光锥求和规则（LCSR）和微扰QCD方法的计算结果进行了比较.我们的结果表明，两种不同版本的求和规则可以导致负责$Λ_b \to p$转变的形状因子的数量一致。从具有渐近$Λ$重子分布振幅的LCSR得到的$Λ_b \to Λ$跃迁形状因子比在$Λ_b$ -重子LCSR中得到的大近一个数量级，这意味着对重子分布振幅的预渐近修正是非常重要的.此外，在$Λ_b$ -重子LCSR框架下，计算了形状因子$f_1^{Λ_b \to p}$和$f_1^{Λ_b \to Λ}$之间的SU（3）对称性破缺效应为$28^{+14}_{-8} %$.

英文摘要：

Light-cone sum rules for the $Λ_b \to p, Λ$ transition form factors are derived from the correlation functions expanded by the twist of the distribution amplitudes of $Λ_b$ baryon. In terms of the $Λ_b$ three-quark distribution amplitudes models constrained by the QCD theory, we calculate the form factors at small momentum transfers and compare the results with that estimated in the conventional light-cone sum rules (LCSR) and perturbative QCD approaches. Our results indicate that the two different version of sum rules can lead to the consistent numbers of form factors responsible for $Λ_b \to p$ transition. The $Λ_b \to Λ$ transition form factors from LCSR with the asymptotic $Λ$ baryon distribution amplitudes are found to be almost one order larger than that obtained in the $Λ_b$-baryon LCSR, implying that the pre-asymptotic corrections to the baryonic distribution amplitudes are of great importance. Moreover, SU(3) symmetry breaking effect between the form factors $f_1^{Λ_b \to p}$ and $f_1^{Λ_b \to Λ}$ are computed as $28^{+14}_{-8} %$ in the framework of $Λ_b$-baryon LCSR.

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