论文标题
QCD在接下来的领先顺序上改善了顶级衰减
QCD improved top-quark decay at next-to-next-to-leading order
论文作者
论文摘要
我们通过使用最大保征原理（PMC）在QCD中的近临界序列（NNLO）处分析了最高的衰减，该原理提供了一种系统的方法来消除扰动QCD预测中的重新归一化方案和规模歧义。耦合常数$α_s$的PMC重归其化量表是通过使用使用重量化组方程（RGE）来控制运行耦合行为的非统一$β$项来确定的。我们获得PMC量表$ q_ \ star = 15.5 $ GEV的顶级衰减，这比传统选择$μ_r= m_t $小的数量级，反映了顶级衰减过程的QCD动力学的微小虚拟性。此外，由于PQCD系列中的非符号$β$项消失，因此没有肾上腺差异，并且与在$μ_r= m_t $中获得的常规结果相比，NNLO QCD校正项被抑制了NNLO QCD校正项，而NLO QCD校正项被大大增加。通过进一步包括临近领先（NLO）的电动校正，有限的$ w $玻色子宽度和有限的底部夸克质量，我们获得了顶级的总衰减宽度$γ^{\ rm tot} _t = 1.3112^{+0.0190} $Δm_t= \ pm0.7 $ gev，耦合常数$Δα_s（m_z）= \ pm0.0009 $以及使用[n/m] = [1/1]的PAA方法对未知高阶项的估计。 PMC改进了顶级衰减的预测，与先前的PMC计算互补，用于Quark对生产，有助于对顶级Quark的性质的详细研究。
We analyse the top-quark decay at the next-to-next-to-leading order (NNLO) in QCD by using the Principle of Maximum Conformality (PMC) which provides a systematic way to eliminate renormalization scheme and scale ambiguities in perturbative QCD predictions. The PMC renormalization scales of the coupling constant $α_s$ are determined by absorbing the non-conformal $β$ terms that govern the behavior of the running coupling by using the Renormalization Group Equation (RGE). We obtain the PMC scale $Q_\star=15.5$ GeV for the top-quark decay, which is an order of magnitude smaller than the conventional choice $μ_r=m_t$, reflecting the small virtuality of the QCD dynamics of the top-quark decay process. Moreover, due to the non-conformal $β$ terms disappear in the pQCD series, there is no renormalon divergence and the NLO QCD correction term is greatly increased while the NNLO QCD correction term is suppressed compared to the conventional results obtained at $μ_r=m_t$. By further including the next-to-leading (NLO) electroweak corrections, the finite $W$ boson width and the finite bottom quark mass, we obtain the top-quark total decay width $Γ^{\rm tot}_t=1.3112^{+0.0190}_{-0.0189}$ GeV, where the error is the squared averages of the top-quark mass $Δm_t=\pm0.7$ GeV, the coupling constant $Δα_s(M_Z)=\pm0.0009$ and the estimation of unknown higher-order terms using the PAA method with [N/M]=[1/1]. The PMC improved predictions for the top-quark decay are complementary to the previous PMC calculations for top-quark pair production and helpful for detailed studies of properties of the top-quark.
