论文标题
$ Z $ BOSON辐射效率衰减到NNLO和LL准确性
$Z$ boson radiative decays to a $P$-wave quarkonium at NNLO and LL accuracy
论文作者
论文摘要
在这项工作中，我们将$ z $玻色子的辐射衰减与光子相关的$ p $ - wave quarkonium $ h $，其中$ h $可以是$χ_{qj} $，$ h_q $，$ q = c = c，b $和$ j = 0,1,1,2 $。在非依赖性QCD（NRQCD）框架内，将螺旋幅度振幅和非极化衰减宽度评估为QCD近代到领先顺序（NNLO）。我们首次以双层订单检查$ H_Q $独家生产的NRQCD分解。 $ M_z^2/m_q^2 $的领先对数（LL）在领先的短途系数中可能会破坏扰动的融合，并通过采用轻度键入分解来重新定位到$α_S$的所有订单。我们发现，对于$χ_{Q2} $和$ H_Q $ Productions的辐射校正是相当大的，而对于其他频道来说是中等甚至次要的。我们还注意到，对于$χ_{c0,2} $和$ H_C $ PRODUCTIONS，LL重新召集可以将衰减宽度的前阶预测更改超过25 \％，而对于$χ_{C1} $生产。但是，LL重新召集对近级和NNLO预测的影响显着减轻。还进行了一些现象学探索。
In this work, we study the radiative decay of $Z$ boson to a $P$-wave quarkonium $H$ in association with a photon, where $H$ can be $χ_{QJ}$, $h_Q$ with $Q=c,b$ and $J=0,1,2$. The helicity amplitudes and the unpolarized decay widths are evaluated up to QCD next-to-next-to-leading order (NNLO) within the framework of nonrelativistic QCD (NRQCD). For the first time, we check the NRQCD factorization for $h_Q$ exclusive production at two-loop order. The leading logarithms (LL) of $m_Z^2/m_Q^2$ in the leading-twist short-distance coefficients, which may potentially ruin the perturbative convergence, are resummed to all orders of $α_s$ by employing the light-cone factorization. We find the radiative corrections are considerable for $χ_{Q2}$ and $h_Q$ productions, while are moderate or even minor for other channels. We also notice that the LL resummation can change the leading-order predictions for decay widths by more than 25\% for $χ_{c0,2}$ and $h_c$ productions, and by around 50\% for $χ_{c1}$ production. However, effects of the LL resummation on the next-to-leading-order and NNLO predictions are notably mitigated. Some phenomenological explorations are also performed.
