【作者】 张瑞；

【导师】 王天鸿；

【作者基本信息】 哈尔滨工业大学 ， 物理学， 2023， 硕士

【摘要】 粒子物理标准模型是目前最成功的物理理论之一。该模型在二十世纪后期被建立后迅速发展,至2012年Higgs粒子被大型强子对撞机(Large Hadron Col-lider)发现,粒子物理标准模型完成了最后一块拼图。对Higgs粒子的各种性质的进一步研究,特别是其与费米子的耦合强度的精确检测成为当前粒子物理领域的重要任务。本文基于粒子物理标准模型研究了Higgs粒子衰变到双轻子以及重夸克偶素的过程。特别是对Higgs粒子与cc以及bb耦合的费曼图的贡献,以及该费曼图与其他费曼图的交叉项贡献进行了有效的分析。本文所研究衰变道的末态介子为J/ψ,ψ(2S),Υ(1S),Υ(2S),Υ(3S),基于Bethe-Salpeter方法计算了不同末态介子的衰变常数。对于Higgs粒子与夸克耦合的费曼图,基于Bethe-Salpeter方法计算了强子跃迁矩阵元,给出了形状因子。H→V+l+l-衰变道有8种不同的费曼图,本文计算了这8种不同费曼图独立贡献的分支比,分析了其关于不变轻子质量S的微分分布。最后完成8种费曼图的交叉项计算之后,得到H→V+l+l-衰变道的衰变分支比,分支比的数量级在10-8到10-6之间。本文发现,当末态轻子为e且S截断值取较小值时,Higgs粒子与夸克耦合的费曼图所贡献的分支比将会大大提高。当S截断值取0.01GeV时,对于末态介子分别为J/ψ,ψ(2S),Υ(1S),Υ(2S),Υ(3S)约占整体的:41.2%,27.3%,32.9%,22.1%,42.1%。同时本文发现对于末态介子为J/ψ,ψ(2S),末态轻子为e,μ时,衰变道的主要贡献来源于三个方面:Higgs粒子与两个Z0玻色子的耦合,Higgs粒子与Zγ(该Z0玻色子可以在壳)的耦合以及Higgs粒子与夸克的耦合。但当末态轻子为τ时,Higgs粒子与轻子的耦合所贡献的分支比将极大的提高,约占据整体的:94.8%、91.9%,衰变道分支比的量级也上升到10-6。而这种现象并未在末态介子Υ及其激发态上,无论是末态轻子为e,μ还是τ,其衰变道分支比的主要贡献都来自Higgs粒子与两个Z0玻色子耦合的费曼图,都占整体的80%左右。更多还原

【Abstract】 The Standard Model of particle physics is currently one of the most successful physical theories.Since the model was established in the late 20th century,it has developed rapidly.By 2012,the Higgs particle was discovered by the Large Hadron Collider(Large Hadron Collider),and the standard model of particle physics completed the last piece of the puzzle.Further research on various properties of Higgs particle,especially the precise detection of its coupling strength with fermions has become an important task in the field of particle physics.In this paper,based on the standard model of particle physics,the process of Higgs particles decaying into dileptons and heavy quarkonium is studied.In particular,the contribution of the Feynman diagram coupled with cc by bb and the contribution of the cross term between the Feynman diagram and other Feynman diagrams are effectively analyzed.The final mesons of the decay channel studied in this paper are J/ψ,ψ(2S),Υ(1S),Y(2S),Y(3S),based on The Bethe-Salpeter method calculates the decay constants of different final state mesons.For the Feynman diagram of the coupling of Higgs particles and quarks,the hadron transition matrix elements are calculated based on the BetheSalpeter method,and the shape factors are given.H→V+l+l-There are eight different Feynman diagrams in the decay channel.This paper calculates the branch ratios of the independent contributions of these eight different Feynman diagrams,and analyzes its relationship with the invariant Differential distribution of lepton mass S.Finally,after completing the calculation of the intersection items of the eight Feynman diagrams,the decay branching ratio of the H→V+l+l-decay channel is obtained.In this paper,we found that when the final state lepton is e and the S cut-off value is small,the contribution branching ratio of the Feynman diagram coupled with Higgs particles and quarks will be greatly increased.When the cut-off value of S is 0.01GeV,the final mesons are J/ψ,ψ(2S),Υ(1S),Υ(2S),Υ(3S)accounts for about the whole:41.2%,27.3%,32.9%,22.1%,42.1%.At the same time,this paper finds that when the final state meson is J/ψ,ψ(2S),and the final state lepton is τ,the branching ratio contributed by the coupling of Higgs particles and leptons will be extremely large Increase,occupying the whole:94.8%,91.9%,and the magnitude of the branching ratio of the decay channel also rises to 10-6.But this phenomenon is not on the final state meson Υ and its excited state,whether the final state lepton is μ or τ,the main contribution of the branch ratio of the decay path comes from the Higgs particle and The Feynman diagrams of two Z0 boson couplings account for about 80%of the whole.更多还原