Measurement of single top-quark production in the s-channel in proton$-$proton collisions at $\mathrm{\sqrt{s}=13}$ TeV with the ATLAS detector

A measurement of single top-quark production in the s-channel is performed in proton--proton collisions at a centre-of-mass energy of $13$ TeV with the ATLAS detector at the CERN Large Hadron Collider. The dataset corresponds to an integrated luminosity of 139 fb$^{-1}$. The analysis is performed on events with an electron or muon, missing transverse momentum and exactly two $b$-tagged jets in the final state. A discriminant based on matrix element calculations is used to separate single top-quark s-channel events from the main background contributions, which are top-quark pair production and $W$-boson production in association with jets. The observed (expected) signal significance over the background-only hypothesis is 3.3 (3.9) standard deviations, and the measured cross-section is $\sigma=8.2^{+3.5}_{-2.9}$ pb, consistent with the Standard Model prediction of $\sigma^{\mathrm{SM}}=10.32^{+0.40}_{-0.36}$ pb.

利用位于欧洲核子研究组织大型强子对撞机CERN的ATLAS探测器，在质子-质子碰撞中，于中心质心能量为13 TeV的条件下，对s通道产生的单顶夸克进行了测量。该数据集对应于139 fb$^{-1}$的积分亮度。分析基于具有电子或μ子、缺失的横动量和最终状态中恰好有两个b标签的喷注的事件。通过矩阵元素计算得到的判别准则，用于将单顶夸克s通道事件与主要背景贡献（顶夸克对产生和与喷注伴随产生的W玻色子）区分开来。在仅考虑背景的假设下，观察到的（预期的）信号显著性超过3.3（3.9）个标准差，测量的截面为$sigma=8.2^{+3.5}_{-2.9}$ pb，与标准模型预测的$sigma^{mathrm{SM}}=10.32^{+0.40}_{-0.36}$ pb相一致。