LHC上top夸克及Higgs玻色子衰变到粲夸克偶素的研究

发布时间：2018-06-26 19:59

本文选题：重夸克偶素 + NRQCD　；参考：《安徽大学》2017年硕士论文

【摘要】：重夸克偶素物理一直都是高能物理中最富有意义的研究课题之一,它为理解微扰和非微扰量子色动力学(QCD)提供了一个丰富而理想的平台。目前,重夸克偶素的产生和衰变过程的理论描述方法——非相对论QCD(NRQCD)依然是该领域中的首要选择,其实验验证是重夸克偶素物理最紧迫的任务之一。自提出以来,NRQCD成功解释了重夸克偶素的大部分实验结果,对研究重夸克偶素相关过程取得了举世瞩目的成就。与此同时,自运行以来,大型强子对撞机(LHC)一直是研究粒子内部结构,发现新粒子以及检验理论模型的最为重要的理想工具。因此,LHC作为我们研究重夸克偶素物理的理想场所,本文以NRQCD因子化方法为基础,在LHC上做了两项工作:top夸克衰变到χcJW+b伴随产生的研究,和Higgs玻色子衰变到J/ψ(r)γ伴随产生的研究。工作一,我们计算了 top夸克衰变到χcJW+b伴随产生的次领头阶(NLO)QCD修正。在此过程中,尽管领头阶(LO)的色八重态(CO)贡献占主要地位,但是由于3PJ(1)(J=0,1,2)Fock态给出重要的负值贡献,经NLOQCD修正后,总的NLO结果不太大。我们的结果表明在LHC上探测top夸克衰变产生χc0是非常困难的,但是χc1和χc2的产生有可能被探测到的。倘若,在LHC上顶夸克衰变到χcJ能被探测到,这不仅对研究top夸克衰变产生J/ψ有帮助,而且对了解重夸克偶素的产生机制有重要的意义。工作二,我们研究了 Higgs玻色子衰变到J/ψ(r)γ伴随产生。对于直接过程,H→J/ψ(r)+γ过程的LO衰变宽度通过NLO QCD修正受到明显压低。至于间接过程,H→γ*γ 通过虚光子γ衰变到J/ψ(r)γ,我们的计算包含了所有标准模型(SM)的费曼图。我们的计算结果表明,间接产生的衰变宽度远远大于直接产生的衰变宽度。由于在实验上非常干净,H→J/ψ(r)+γ衰变过程在14TeV LHC上有可能被观测到,它提供了一种新的方式去探测LHC上的Yukawa耦合和新物理。本文的创新之处在于,我们在LHC上研究了 top夸克及Higgs玻色子衰变到粲夸克偶素过程,并首次进行NLO QCD修正。我们的结果表明,经过NLO QCD修正后,在LHC上很有可能探测到χc1和χc2的产生,及Higgs玻色子与底夸克的Yukawa耦合。如果将来在LHC上能探测到这些性过程,这将为检验理论模型和探索新物理提供重要的参考。
[Abstract]:Heavy quark physics has always been one of the most significant research topics in high energy physics. It provides a rich and ideal platform for understanding perturbation and non-perturbation quantum chromodynamics (QCD). At present, non-relativistic QCD (NRQCD), a theoretical description method for the production and decay process of heavy quarklides, is still the first choice in this field, and its experimental verification is one of the most urgent tasks in the physics of heavy quarks. Since its introduction, NRQCD has successfully explained most of the experimental results of heavy quarks, and has made great achievements in the study of heavy quark related processes. At the same time, since its operation, the large Hadron Collider (LHC) has been the most important ideal tool to study the internal structure of particles, find new particles and test theoretical models. Therefore, LHC is an ideal place for us to study heavy quark physics. Based on the NRQCD factorization method, two studies have been done on the LHC in which: top quark decays to 蠂 cJW b and Higgs boson decays to J / 蠄 (r) 纬. In the first work, we calculate the subleader order (NLO) QCD correction of top quark decay to 蠂 c JW b. In this process, although the leading order (Lo) chromatic octave (CO) contribution is dominant, the total NLO result is not very large due to the important negative contribution of the 3PJ (1) (JOO 1 / 2) Fock state. After NLOQCD correction, the total NLO results are not very large. Our results show that it is very difficult to detect the top quark decay generation 蠂 _ c _ 0, but the production of 蠂 _ c _ 1 and 蠂 _ c _ 2 is likely to be detected. If the top quark decay over top can be detected to 蠂 cJ, it will not only be helpful to study the generation of J / 蠄 in top quark decay, but also be of great significance in understanding the production mechanism of heavy quark quarks. In the second work, we study the decay of the Higgs boson to J / 蠄 (r) 纬 accompanied production. For the direct process, the Lo decay width of the J / 蠄 (r) 纬 process is significantly depressed by the NLO QCD correction. As for the indirect process, H ~ + 纬 ~ * 纬 decays to J / 蠄 (r) 纬 via virtual photon 纬, our calculation includes all the Ferman graphs of the standard model (SM). Our results show that the indirectly generated decay width is much larger than the directly generated decay width. Due to the fact that the J / 蠄 (r) 纬 decay process may be observed at 14TeV LHC experimentally, it provides a new way to detect Yukawa coupling and new physics on the LHC. The innovation of this paper is that we have studied the decay of top quarks and Higgs bosons to charmed quarks on the LHC, and have carried out the NLO QCD correction for the first time. Our results show that it is possible to detect the production of 蠂 c 1 and 蠂 c 2 and the coupling of Higgs boson with Yukawa of bottom quark in LHC after NLO QCD correction. If these processes can be detected on the LHC in the future, this will provide an important reference for the examination of theoretical models and the exploration of new physics.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O572.33

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