Study of heavy-flavor quarks produced in association with top-quark pairs at s = 7 TeV using the ATLAS detector
Study of heavy-flavor quarks produced in association with top-quark pairs at s = 7 TeV using the ATLAS detector
复制标题
使用 ATLAS 探测器研究与 s = 7 TeV 的顶夸克对相关的重味夸克
DOI：
10.1103/physrevd.89.072012
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发表时间：
2014
影响因子：
5
通讯作者：
Aad G
中科院分区：
文献类型：
--
作者：
Aad G
利用双轻子顶夸克对（ttbar）候选事例，研究了顶夸克对与重味夸克（HF）的产生，ttbar+B+X或ttbar+c+X，统称为ttbar+HF.所使用的数据集对应于在欧洲核子研究中心大型强子对撞机的ATLAS探测器记录的质量中心能量为7 TeV的质子-质子碰撞的积分光度为4.7 fb-1。通过寻找至少有三个b-标记喷流的事件来推断ttbar样本中存在额外的HF夸克，其中两个归因于ttbar衰变的b-夸克，第三个归因于额外的HF产生。该样本中ttbar+HF的主要背景是ttbar+喷流事件，其中将淡味喷流错误识别为重味喷流。为了确定额外的b-标记射流的重口味和轻口味含量，对样品中b-标记射流的顶点质量分布进行拟合。拟合结果显示，79 +/- 14（统计）+/- 22（系统）在105个选定的额外的b-标记喷流中，有一个来自HF夸克，与零ttbar+HF产生的假设相差三个标准差。额外HF产生的结果被引用为ttbar+HF产生的横截面与具有至少一个附加射流的ttbar产生的横截面的比率（R_HF）。在ATLAS验收范围内的基准运动区域中测量两个横截面。R_HF测得为[6.2 +/- 1.1（stat.）+/- 1.8（系统）]%对于pT>25 GeV的喷流，|eta| <2.5，与Monte Carlo生成器的预期一致。
Using a sample of dilepton top-quark pair (ttbar) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, ttbar+b+X or ttbar+c+X, collectively referred to as ttbar+HF. The dataset used corresponds to an integrated luminosity of 4.7 fb-1 of proton--proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF quarks in the ttbar sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b-quarks from the ttbar decays and the third to additional HF production. The dominant background to ttbar+HF in this sample is ttbar+jet events in which a light-flavor jet is misidentified as a heavy-flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79 +/- 14 (stat.) +/- 22 (syst.) of the 105 selected extra b-tagged jets originate from HF quarks, three standard deviations away from the hypothesis of zero ttbar+HF production. The result for extra HF production is quoted as a ratio (R_HF) of the cross section for ttbar+HF production to the cross section for ttbar production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. R_HF is measured to be [6.2 +/- 1.1 (stat.) +/- 1.8 (syst.)]% for jets with pT>25 GeV and |eta|<2.5, in agreement with the expectations from Monte Carlo generators.