基于QCD光锥求和规则的Λ_b→N(1520)ℓ⁻ν̅_ℓ半轻子衰变
Semileptonic Decay of $Λ_b \rightarrow N(1520)\ell^-\barν_{\ell}$ from QCD Light-cone Sum Rules
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中文总结 AI 辅助
本研究用QCD光锥求和规则计算Λ_b→N(1520)半轻子衰变的形状因子，预测相关可观测量，结果可作为实验理论基准。
中文摘要 AI 辅助
我们利用QCD光锥求和规则（LCSRs）研究带电流跃迁Λ_b⁰→N(1520)⁺的整套矢量和轴矢量形状因子，该规则基于Λ_b重子的光锥分布振幅（LCDAs），硬散射核在树图阶计算。在关联函数的强子表示中，我们包含负宇称N(1520)（J^P=3/2⁻）和正宇称N(1720)（J^P=3/2⁺）的极点贡献。通过匹配选定的洛伦兹结构，我们在采用的双极点强子假设内推导求和规则，以分离N(1520)与N(1720)的贡献。在使用线性阶截断的极点改进z展开将大反冲LCSR结果外推至物理q²区域后，我们预测Λ_b⁰→N(1520)⁺ℓ⁻ν̅_ℓ（ℓ=e,μ,τ）的微分分支比、轻子前后不对称性、带电轻子极化以及N(1520)的极化。对应的总分支比为ℬ_{e,μ,τ}=(12.4±10.5,12.4±10.5,5.0±4.3)×10⁻⁵。在所述近似下，这些结果可作为该道未来实验研究的理论基准。
英文摘要
We investigate the complete set of vector and axial-vector form factors for the charged-current transition $Λ_b^0\to N(1520)^+$ using QCD light-cone sum rules (LCSRs) based on the light-cone distribution amplitudes (LCDAs) of the $Λ_b$ baryon, with the hard-scattering kernels evaluated at tree level. In the hadronic representation of the correlation function, we include the pole contributions of both the negative-parity $N(1520)$, with $J^P=3/2^-$, and the positive-parity $N(1720)$, with $J^P=3/2^+$. By matching a selected set of Lorentz structures, we derive sum rules that separate the $N(1520)$ contribution from the $N(1720)$ contribution within the adopted two-pole hadronic ansatz. After extrapolating the large-recoil LCSR results over the physical $q^2$ region using a pole-improved $z$ expansion truncated at linear order, we predict the differential branching fractions, the lepton forward-backward asymmetry, the charged-lepton polarization, and the $N(1520)$ polarization in $Λ_b^0\to N(1520)^+\ell^-\barν_{\ell}$ ($\ell=e,μ,τ$). The corresponding total branching fractions are $\mathcal{B}_{e,μ,τ} =(12.4\pm10.5,\,12.4\pm10.5,\,5.0\pm4.3)\times10^{-5}$. Within the stated approximations, these results may serve as theoretical benchmarks for future experimental studies of this channel.
