arXiv 1503.069072015-03-24hep-ph

用Bethe-Salpeter方程方法研究$Λ_b\rightarrow~ Λl^+l^-$和$Λ_b\rightarrow p l \barν$衰变

Study of $Λ_b\rightarrow~ Λl^+l^-$ and $Λ_b\rightarrow p l \barν$ decays in the Bethe-Salpeter equation approach

Y. Liu, L. -L. Liu, X. -H. Guo

摘要：

在我们以前的工作中，基于$SU(6)$自旋味波函数，我们把$Λ$和$p$看作是由不同的夸克-双夸克组态组成，建立了夸克和标量双夸克组态的Bethe-Salpeter（BS）方程。在我们目前的工作中，我们应用该模型来计算标准模型（SM）中半轻子跃迁$Λ_b\rightarrowΛl^+l^-$ $(l=μ,e,τ)$和$Λ_b\rightarrow p l\barν$的形状因子。衰变$Λ_b\rightarrowΛμ^+μ^-$是特别有趣的，因为它已经在CDF和LHCb合作中测量，这种罕见的衰变对新的物理效应非常敏感。$Λ_b\rightarrow p l\barν$衰变是在大型强子对撞机上测量Cabibbo-Kobayashi-Maskawa矩阵元$|V_{ub}|$的一种很有前途的模式。在我们的计算中，根据BS方程核中双夸克质量和夸克与双夸克相互作用强度等模型参数的取值范围，我们发现，在我们的模型中，$Λ_b\rightarrowΛμ^+μ^-$的分支比与实验数据是一致的，目前LHCb的实验结果与我们计算的$Λ_b\rightarrowΛμ^+μ^-$的微分分支比一致，只是在较大的范围内动量传递区这表明仍有可能产生新的物理效应的空间。我们也给出了$Λ_b\rightarrowΛl^+l^-$和$Λ_b\rightarrow p l\barν$的总分支比与其它唯象方法的结果的比较。

英文摘要：

In our previous work, based on the $SU(6)$ spin-flavor wave function, we regard $Λ$ and $p$ as composed of different quark-diquark configurations and established the Bethe-Salpeter (BS) equations of configurations for quark and scalar diquark. In our present work, we apply this model to calculate the form factors of the semileptonic transitions $Λ_b\rightarrowΛl^+l^-$ $(l=μ,e,τ)$ and $Λ_b\rightarrow p l\barν$ within the Standard Model (SM). The decay $Λ_b\rightarrowΛμ^+μ^-$ is especially interesting since it has been measured in CDF and LHCb Collaborations and this rare decay is very sensitive to new physics effects. The decay $Λ_b\rightarrow p l\barν$ is a promising mode for the measurement of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ at the Large Hadron Collider. In our calculations, depending on the ranges of the parameters in the model including the diquark mass and the interaction strength between the quark and the diquark in the kernel of the BS equation, we find that the branching ratio of $Λ_b\rightarrowΛμ^+μ^-$ in our model is consistent with the experimental data and the current experimental results from LHCb agree with the differential branching ratio of $Λ_b\rightarrowΛμ^+μ^-$ from our calculation except at the lager momentum transfer region. This indicates that there is still room for possible new physics effects. We also give comparisions of the total branching ratios of $Λ_b\rightarrowΛl^+l^-$ and $Λ_b\rightarrow p l\barν$ with those given by other phenomenological methods.

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。

摘要：

英文摘要：

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