论文标题
大型$ t \至cz $作为$ w $质量的矢量状夸克的标志
Large $t\to cZ$ as a Sign of Vector-Like Quarks in Light of the $W$ Mass
论文作者
论文摘要
稀有风味变化的顶级夸克衰减$ t \ to cz $是新物理学的明显迹象，并且由于LHC生产的顶级夸克数量大量，因此在实验上非常有趣。但是，很少有（可行的）模型可以生成$ t \ to cz $的较高的分支比率 - 实际上，类似矢量的夸克似乎是唯一的现实选择。在本文中，我们调查了类似矢量的夸克（$ u $，$ q_1 $和$ q_7 $）的所有三个表示（根据标准模型量规组），这些夸克（$ u $，$ q_1 $ and $ q_7 $）都可以生成$ t \ to cz $的可观分支比率，而不会违反$ b $物理学的界限。重要的是，这些正是三个矢量般的夸克，可以通过耦合到$ w $质量的预测进行相当大的积极转变，这也可以通过耦合到最高的Quark（$ t \ to cz $）所需的顶级夸克。在标准模型有效的现场理论上计算并使用类似向量的夸克的单循环匹配，我们发现Br（$ t \ to Cz $）的顺序可能为$ 10^{ - 6} $，$ 10^{ - 5} $，$ 10^{ - 5} $和$ 10^{ - 4}^{ - 4} $ $ $ $ $ u $，$ q_1 $和$ q_ $ q_ $ q_ $ q_ $ qu_ $ y，以及三个$ q_7 $ y，以及your thr thr thr thr thr thr thr thr thtry是y的，并且相应地atter an容纳。
The rare flavour changing top quark decay $t\to cZ$ is a clear sign of new physics and experimentally very interesting due to the huge number of top quarks produced at the LHC. However, there are few (viable) models which can generate a sizable branching ratio for $t\to cZ$ -- in fact vector-like quarks seem to be the only realistic option. In this paper, we investigate all three representations (under the Standard Model gauge group) of vector-like quarks ($U$, $Q_1$ and $Q_7$) that can generate a sizable branching ratio for $t\to cZ$ without violating bounds from $B$ physics. Importantly, these are exactly the three vector-like quarks which can lead to a sizable positive shift in the prediction for $W$ mass, via the couplings to the top quark also needed for a sizable Br($t\to cZ$). Calculating and using the one-loop matching of vector-like quarks on the Standard Model Effective Field Theory, we find that Br($t\to cZ$) can be of the order of $10^{-6}$, $10^{-5}$ and $10^{-4}$ for $U$, $Q_1$ and $Q_7$, respectively and that in all three cases the large $W$ mass measurement can be accommodated.
