论文标题
调查颜色抑制的衰减$λ_b\rightarrowλψ$在扰动QCD方法中
Investigating the color-suppressed decays $Λ_b\rightarrow Λψ$ in the perturbative QCD approach
论文作者
论文摘要
根据扰动QCD方法研究了非律师两体$λ_b\rightArrowλψ$用$ψ= j/ψ$或$ψ$或$ψ（2s）$衰减。这些是色彩抑制的过程，在这些过程中，不可侵略的贡献被确认为主导。角动量保护使我们能够描述相关的衰变，并通过四个独立的复杂螺旋幅度幅度来描述。据观察，$λ$ baryon的负疗法状态是预期的，这是带电 - 电流相互作用的左手性质。获得的螺旋性幅度的结果用于计算分支比率和各种可观察的参数，然后将其与现有的理论预测和实验数据进行比较。特别是，我们预测比率$ \ MATHCAL {r} = \ frac {\ Mathcal {b}（λ_b\rightarrowλψ（2s））}} {\ Mathcal {b}（λ_b\ rightArrow lowarowλj/ψ）} = 0.47^= 0.47^= 0.47^= 0.02} $ 0.508 \ pm 0.023 $从粒子数据组处于1个标准偏差的水平。我们还简要探讨了对半衰减的$λ_b\rightarrowλl^+l^ - $ $ $衰减的长距离贡献，在该区域，DiLepton不变的群众约为$ j/ψ$和$ψ$和$ψ（2s）$ resonances $。
The nonleptonic two-body $Λ_b\rightarrow Λψ$ decays with $ψ=J/ψ$ or $ψ(2S)$ are investigated based on the perturbative QCD approach. These are color-suppressed processes in which the nonfactorizable contributions are confirmed to be dominant. Angular momentum conservation allows us to describe the concerned decays by four independent complex helicity amplitudes. It is observed that the negative-helicity states for the $Λ$ baryon are preferred as expected in the left-handed nature of the charged-current interaction. The obtained results for the helicity amplitudes are used to compute the branching ratios and various observable parameters, which are then compared to the existing theoretical predictions and experimental data. In particular, we predict the ratio $\mathcal{R}=\frac{\mathcal{B}(Λ_b\rightarrowΛψ(2S))}{\mathcal{B}(Λ_b\rightarrowΛJ/ψ)}=0.47^{+0.02}_{-0.00}$ in comparison with $0.508\pm 0.023$ from the Particle Data Group at the level of 1 standard deviation. We also briefly explore the long-distance contributions to the semileptonic $Λ_b \rightarrow Λl^+l^-$ decays in the kinematic regions where the dilepton invariant masses are around the $J/ψ$ and $ψ(2S)$ resonances.
