论文标题
注意稀有$ z $ -boson衰减要加倍夸克尼亚
Note on rare $Z$-boson decays to double heavy quarkonia
论文作者
论文摘要
在标准型号中，我们研究了稀有的$ z $ -boson腐烂，分别用$ v $，$ z \ to vv $和$ z \ to vp $，分别用$ v $表示矢量和$ p $表示伪斯卡利亚quarkonia。假定前阶QCD图将对这些过程提供主要贡献，例如，估计$ {\ cal b}（z \ to j/ψj/ψ）$估计约为$ 10^{-13} $。但是，这些衰减也可能通过电磁过渡到Vγ^*$和$ z \ toPγ^*$发生，而虚拟光子转换为$ V $。有趣的是，相对于QCD的贡献，矢量夸克质量的较小可能会引起巨大的因子$ m_z^2/m_v^2 $，因此可以抵消电磁耦合的抑制。我们系统地将这两种类型的贡献包括在计算中，以预测这些衰减的分支分数。特别是由于虚拟光子效应，发现$ {\ cal b}（z \ to j/ψj/ψ）$将得到显着增强，最高可达$ 10^{ - 10} $。
Within the standard model, we have investigated rare $Z$-boson decays into double heavy quarkonia, $Z\to VV$ and $Z\to VP$ with $V$ denoting vector and $P$ denoting pseudoscalar quarkonia, respectively. It is assumed that the leading-order QCD diagrams would give the dominant contributions to these processes, and the corresponding branching fractions, for instance, ${\cal B}(Z\to J/ΨJ/Ψ)$ has been estimated to be around $10^{-13}$ in the literature. However, these decays could also happen through the electromagnetic transition $Z\to Vγ^*$ and $Z\to Pγ^*$, with the virtual photon transforming into $V$. Interestingly, the smallness of the vector quarkonium mass can give rise to a large factor $m_Z^2/m_V^2$, relative to the QCD contributions, which thus counteracts the suppression from the electromagnetic coupling. We systematically include these two types of contributions in our calculation to predict branching fractions for these decays. Particularly, due to the virtual photon effects, it is found that ${\cal B}(Z\to J/ΨJ/Ψ)$ will be significantly enhanced, which could be up to $10^{-10}$.
