AI 中文总结
利用ATLAS探测器13 TeV数据搜索顶夸克产生和衰变中的带电轻子味破坏，未发现超出标准模型的信号，并给出Wilson系数和分支比的上限。
AI 中文摘要
本文报道了对顶夸克产生和衰变中带电轻子味破坏（cLFV）的搜索。所分析的数据对应于大型强子对撞机上ATLAS探测器记录的质心能量为$\sqrt{s}=13$ TeV的质子-质子碰撞，积分亮度为140 fb$^{-1}$。可能的cLFV贡献通过两种机制进行研究。第一种机制是产生一个轻子衰变的单顶夸克，并伴随一对带相反电荷、不同味道的轻子。第二种机制是产生顶夸克对，其中一个顶夸克衰变为一对带相反电荷、不同味道的轻子和一个$u$-或$c$-夸克，而另一个顶夸克根据标准模型衰变为一个轻子衰变的$W$玻色子和一个$b$-夸克。信号过程包含三个带电轻子，取为电子或缪子。未观察到与标准模型预测的显著偏差，这些结果在有效场论框架内进行解释。在95%置信水平上对六个Wilson系数设置了上限，范围从张量$u$-夸克耦合的$|C^{\mathrm{tensor}}_{e\mu tu}|/\Lambda^2 < 0.018$ TeV$^{-2}$到标量$c$-夸克耦合的$|C^{\mathrm{scalar}}_{e\mu tc}|/\Lambda^2 < 0.32$ TeV$^{-2}$。这些Wilson系数限制被转换为95%置信水平上cLFV顶夸克衰变分支比的上限，范围从标量$u$-夸克耦合的$B(t \to e\mu u) < 6 \cdot 10^{-9}$到张量$c$-夸克耦合的$B(t \to e\mu c) < 2.7 \cdot 10^{-7}$。
英文摘要
A search for charged-lepton-flavour violation (cLFV) in top-quark production and decay is presented. The data analysed correspond to 140 fb$^{-1}$ of proton-proton collisions recorded at a centre-of-mass energy of $\sqrt{s}= 13$ TeV by the ATLAS detector at the Large Hadron Collider. The possible cLFV contribution is studied via two mechanisms. The first is via the production of a leptonically-decaying single-top quark in association with a pair of oppositely-charged different-flavour leptons. The second is the production of top-quark pairs, where one top quark decays into a pair of oppositely-charged different-flavour leptons and a $u$- or $c$-quark, while the other decays into a leptonically-decaying $W$ boson and a $b$-quark, according to the Standard Model. The signal processes contain three charged leptons, taken to be electrons or muons. No significant deviation from the Standard Model prediction is observed, and these results are interpreted within an Effective Field Theory framework. Upper limits are placed at 95% confidence level on six Wilson coefficients, ranging from $|C^{\mathrm{tensor}}_{eμtu}|/Λ^2 < 0.018$ TeV$^{-2}$ to $|C^{\mathrm{scalar}}_{eμtc}|/Λ^2 < 0.32$ TeV$^{-2}$ for the tensor $u$-quark and scalar $c$-quark couplings, respectively. These Wilson coefficient limits are translated into 95% confidence level upper limits on cLFV top-quark decay branching ratios, ranging from $B(t \to eμu) < 6 \cdot 10^{-9}$ to $B(t \to eμc) < 2.7 \cdot 10^{-7}$ for the scalar $u$-quark and tensor $c$-quark couplings, respectively.
Comments51 pages in total, author list starting page 34, 5 figures, 10 tables, submitted to JHEP. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2023-35
