Search for top quark decays t->Hq with 36 fb^{−1} of pp collision data at √s= 13 TeV with the ATLAS detector
Search for top quark decays t->Hq with 36 fb^{−1} of pp collision data at √s= 13 TeV with the ATLAS detector
复制标题
使用 ATLAS 探测器在 ≤s= 13 TeV 处使用 36 fb^{≤1} 的 pp 碰撞数据搜索顶夸克衰变 t->Hq
DOI：
10.1007/jhep05(2019)123
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
ATLAS Collaboration
中科院分区：
文献类型：
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作者：
ATLAS Collaboration
提出了对顶夸克到上型夸克 (q= u, c) 和标准模型希格斯玻色子 t→ Hq 的风味变化中性流衰变的搜索。该搜索基于 2015 年和 2016 年使用 CERN 大型强子对撞机的 ATLAS 探测器记录的 pp 碰撞数据集，对应于 36.1 fb−1 的积分光度。执行两个互补分析来搜索顶夸克对事件，其中一个顶夸克衰变为 Wb，另一个顶夸克衰变为 Hq，目标为 H→ τ+分别为 τ− 衰减模式。两项分析分别利用了 b 夸克喷流的高度多重性，或强子衰变 τ 轻子的存在。多变量技术用于将信号与背景分离，背景主要是顶夸克对的产生。没有发现明显超出背景预期的事件，并且推导出 t→ Hq 支化比的 95% CL 上限。这些搜索与双光子和多轻子最终状态中的 ATLAS 搜索的组合产生了观察到的（预期的）t→ Hc 和 t→ Hu 分支比 95% CL 上限，分别为 1.1× 10− 3 (8.3× 10− 4) 和 1.2× 10− 3 (8.3× 10− 4)。相应的观察到（预期）上限| λ tch|和| λ tuH|耦合系数分别为 0.064 (0.055) 和 0.066 (0.055)。
A search for flavour-changing neutral current decays of a top quark into an up-type quark (q= u, c) and the Standard Model Higgs boson, t→ Hq, is presented. The search is based on a dataset of pp collisions at= 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 36.1 fb− 1. Two complementary analyses are performed to search for top-quark pair events in which one top quark decays into Wb and the other top quark decays into Hq, and target theand H→ τ+ τ− decay modes, respectively. The high multiplicity of b-quark jets, or the presence of hadronically decaying τ-leptons, is exploited in the two analyses respectively. Multivariate techniques are used to separate the signal from the background, which is dominated by top-quark pair production. No significant excess of events above the background expectation is found, and 95% CL upper limits on the t→ Hq branching ratios are derived. The combination of these searches with ATLAS searches in diphoton and multilepton final states yields observed (expected) 95% CL upper limits on the t→ Hc and t→ Hu branching ratios of 1.1× 10− 3 (8.3× 10− 4) and 1.2× 10− 3 (8.3× 10− 4), respectively. The corresponding combined observed (expected) upper limits on the| λ tcH| and| λ tuH| couplings are 0.064 (0.055) and 0.066 (0.055), respectively.