Search for pair production of up-type vector-like quarks and for four-top-quark events in final states with multiple b-jets with the ATLAS detector
Search for pair production of up-type vector-like quarks and for four-top-quark events in final states with multiple b-jets with the ATLAS detector
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DOI：
10.1007/jhep07(2018)089
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发表时间：
2018-03
影响因子：
5.4
通讯作者：
M. Aaboud;G. Aad;B. Abbott;O. Abdinov;Baptiste Abeloos;S. Abidi;O. AbouZeid;N. Abraham
中科院分区：
文献类型：
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作者：
M. Aaboud;G. Aad;B. Abbott;O. Abdinov;Baptiste Abeloos;S. Abidi;O. AbouZeid;N. Abraham
本文研究了上型矢量类夸克（T）的对产生，它具有一个顶夸克和一个标准模型希格斯玻色子或一个Z玻色子的显著分支比。同样的分析也被用于在几个新的物理场景中寻找四顶夸克的产生。该搜索基于2015年和2016年在欧洲核子研究中心大型强子对撞机上使用ATLAS探测器记录的TeV pp碰撞数据集，对应的积分光度为36.1 fb− 1。数据分析轻子+射流的最终状态，其特征在于由一个孤立的电子或μ子与高的横向动量，大失踪的横向动量和多个射流，以及射流+ E小姐T的最终状态，其特征在于由多个射流和大失踪的横向动量。该搜索利用了被确定为源自b夸克的喷流的高度多样性，以及被重建为大半径喷流的强子衰变顶夸克和希格斯玻色子的存在，这是信号事件的特征。未观察到显著超出标准模型预期的情况，并在考虑的不同信号过程的生产横截面上设定了95% CL上限。在几种分支比假设下，利用这些截面极限导出了T→ W B，Zt，Ht衰变贡献下类矢量T夸克质量的下限。95%CL观察到T夸克质量范围的下限为0。99 TeV和1. 43 TeV的分支比的所有可能的值到三个衰变模式考虑，显着扩展超出以前的搜索范围。此外，反常四顶夸克产生的上限是在有效场论模型的背景下设定的，以及在一个普遍的额外维度模型。
A search for pair production of up-type vector-like quarks (T) with a significant branching ratio into a top quark and either a Standard Model Higgs boson or a Z boson is presented. The same analysis is also used to search for four-top-quark production in several new physics scenarios. The search is based on a dataset of pp collisions atTeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb− 1. Data are analysed in the lepton+ jets final state, characterised by an isolated electron or muon with high transverse momentum, large missing transverse momentum and multiple jets, as well as the jets+ E miss T final state, characterised by multiple jets and large missing transverse momentum. The search exploits the high multiplicity of jets identified as originating from b-quarks, and the presence of boosted, hadronically decaying top quarks and Higgs bosons reconstructed as large-radius jets, characteristic of signal events. No significant excess above the Standard Model expectation is observed, and 95% CL upper limits are set on the production cross sections for the different signal processes considered. These cross-section limits are used to derive lower limits on the mass of a vector-like T quark under several branching ratio hypotheses assuming contributions from T→ W b, Zt, Ht decays. The 95% CL observed lower limits on the T quark mass range between 0. 99 TeV and 1. 43 TeV for all possible values of the branching ratios into the three decay modes considered, significantly extending the reach beyond that of previous searches. Additionally, upper limits on anomalous four-top-quark production are set in the context of an effective field theory model, as well as in an universal extra dimensions model.