论文标题
$λ_b^0 \toλ_c^+（\toλ^0π^+）τ^ - （\至π^ - ν_τ）\barν_τ$ decay的可测量角分布
The measurable angular distribution of $Λ_b^0 \to Λ_c^+ (\to Λ^0 π^+)τ^- (\to π^- ν_τ)\barν_τ$ decay
论文作者
论文摘要
在$λ_b^0 \toλ_c^+（\toλ^0π^+）τ^ - \barν_τ$衰减，无法精确确定最终状态粒子$τ^ - $的实体角度，因为$τ^ - $的衰减产物包括未发现的$ν_τ$。因此，无法测量该衰减的角度分布。在这项工作中，我们通过考虑随后的衰减$τ^ - \toπ^ - ν_τ$来构建一个{\ IT可测量}角分布。完整的级联衰变为$λ_b^0 \toλ_c^+（\toλ^0π^+）τ^ - （\toπ^ - ν_τ）\barν_τ$。可以测量最终状态粒子$λ^0 $，$π^+$和$π^ - $的三摩托马。考虑到新物理学（NP）有效算子的所有Lorentz结构和一个未偏光的初始$λ_b$状态，可以用十个Angular可观测值$ {\ Cal K} _i（q^2，e_π）$表示五倍的差分分布。通过整合五个运动学参数中的某些，我们定义了许多可观察的物品，例如$λ_c$ spin偏光$ k} _i（q^2）$。我们为整个Angular Observables $ \ wideHat {\ cal k} _i（q^2）$和$ \ wideHat {\ cal k} _i $提供了数值结果。我们发现，可以在$ \ bar {b} \到d^{（*）}τ^ - \barν_τ$衰减中解决异常的NP对Angular observables $ \ wideHat {\ cal K} _i（q^2）$，$ \ k k} $ \ wideHat {\ cal k} _ {1cc}（q^2）$。
In $Λ_b^0 \to Λ_c^+ (\to Λ^0 π^+) τ^- \barν_τ$ decay, the solid angle of the final-state particle $τ^-$ cannot be determined precisely since the decay products of the $τ^-$ include an undetected $ν_τ$. Therefore, the angular distribution of this decay cannot be measured. In this work, we construct a {\it measurable} angular distribution by considering the subsequent decay $τ^- \to π^- ν_τ$. The full cascade decay is $Λ_b^0 \to Λ_c^+ (\to Λ^0 π^+)τ^- (\to π^- ν_τ)\barν_τ$. The three-momenta of the final-state particles $Λ^0$, $π^+$, and $π^-$ can be measured. Considering all Lorentz structures of the new physics (NP) effective operators and an unpolarized initial $Λ_b$ state, the five-fold differential angular distribution can be expressed in terms of ten angular observables ${\cal K}_i (q^2, E_π)$. By integrating over some of the five kinematic parameters, we define a number of observables, such as the $Λ_c$ spin polarization $P_{Λ_c}(q^2)$ and the forward-backward asymmetry of $π^-$ meson $A_{FB}(q^2)$, both of which can be represented by the angular observables $\widehat{\cal K}_i (q^2)$. We provide numerical results for the entire set of the angular observables $\widehat{\cal K}_i (q^2)$ and $\widehat{\cal K}_i$ both within the Standard Model and in some NP scenarios, which are a variety of best-fit solutions in seven different NP hypotheses. We find that the NP which can resolve the anomalies in $\bar{B} \to D^{(*)} τ^- \barν_τ$ decays has obvious effects on the angular observables $\widehat{\cal K}_i (q^2)$, except $\widehat{\cal K}_{1ss} (q^2)$ and $\widehat{\cal K}_{1cc} (q^2)$.
