This Letter presents evidence for single top-quark production in the
$s$-channel using proton-proton collisions at a centre-of-mass energy of 8 TeV
with the ATLAS detector at the CERN Large Hadron Collider. The analysis is
performed on events containing one isolated electron or muon, large missing
transverse momentum and exactly two $b$-tagged jets in the final state. The
analysed data set corresponds to an integrated luminosity of 20.3 fb$^{-1}$.
The signal is extracted using a maximum-likelihood fit of a discriminant which
is based on the matrix element method and optimized in order 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 heavy-flavour jets. The measurement leads to an observed signal
significance of 3.2 standard deviations and a measured cross-section of
$\sigma_s=4.8\pm0.8$(stat.)$^{+1.6}_{-1.3}$(syst.) pb, which is consistent with
the Standard Model expectation. The expected significance for the analysis is
3.9 standard deviations.

本文提出了用 ATLAS 探测器在 CERN LHC 上，以 8 TeV 质心能量的质子 - 质子碰撞中，采用一个孤立的电子或轻子，一个大的失踪横动量和恰好两个 $b$ 标记喷流的事件，获得了单顶夸克 $s$- 通道的单粒子产生的证据，并得到了测量出的截面，证实了标准模型的预期。

利用矩阵元方法在 ATLAS 探测器中证实 8 TeV 质心能量的质子 - 质子碰撞中存在单顶夸克产生的 s 通道

Evidence for single top-quark production in the $s$-channel in  proton-proton collisions at $\sqrt{s}=$8 TeV with the ATLAS detector using  the Matrix Element Method