论文标题
核核碰撞核中最高夸克的证据
Evidence for top quark production in nucleus-nucleus collisions
论文作者
论文摘要
超级型重离子碰撞在实验室中重现了早期宇宙中盛行的热力学条件，最高可达10 $^{ - 6} $秒，从而允许研究夸克 - 格鲁隆plasma（QGP），Quark-gluon plasma（QGP），量子铬动力学（QCD）的状态（QCD）与折磨的小组群有关。在CERN LHC的核核碰撞中可以访问最重的基本粒子，最重的基本粒子可访问，并且构成了QGP的新型探针。在这里，我们使用铅核碰撞数据在CMS实验记录的5.02 TEV TEV的核子核中心能量上使用Lead-Lead碰撞数据报告了有史以来第一个在核核碰撞中产生顶级夸克的证据。两种方法用于测量顶部夸克对生产的横截面（$σ_\ mathrm {t \ bar {t}} $），通过衰减到带电的leptons（电子或muons）和底部夸克中。一种方法仅依赖于松性信息，而第二种方法还利用了底部夸克的存在。测量的横截面，$σ_\ Mathrm {t \ bar {t}} = $ 2.54 $^{+0.84} _ { - 0.74} $和2.03 $^{+0.71} _ { - 0.71} _ { - 0.64} $ $ $ $ b，分别与预期的数据相结合。
Ultrarelativistic heavy ion collisions recreate in the laboratory the thermodynamical conditions prevailing in the early universe up to 10$^{-6}$ seconds, thereby allowing the study of the quark-gluon plasma (QGP), a state of quantum chromodynamics (QCD) matter with deconfined partons. The top quark, the heaviest elementary particle known, is accessible in nucleus-nucleus collisions at the CERN LHC, and constitutes a novel probe of the QGP. Here, we report the first-ever evidence for the production of top quarks in nucleus-nucleus collisions, using lead-lead collision data at a nucleon-nucleon centre-of-mass energy of 5.02 TeV recorded by the CMS experiment. Two methods are used to measure the cross section for top quark pair production ($σ_\mathrm{t\bar{t}}$) via the decay into charged leptons (electrons or muons) and bottom quarks. One method relies on the leptonic information alone, and the second one exploits, in addition, the presence of bottom quarks. The measured cross sections, $σ_\mathrm{t\bar{t}} = $ 2.54 $^{+0.84}_{-0.74}$ and 2.03 $^{+0.71}_{-0.64}$ $μ$b, respectively, are compatible with expectations from scaled proton-proton data and QCD predictions.
