高能对撞机上三规范玻色子产生的精确研究

发布时间：2018-05-28 21:46

本文选题：标准模型 + 大额外维模型　；参考：《中国科学技术大学》2016年博士论文

【摘要】：标准模型是迄今为止人类所构造的最成功的粒子物理理论,随着Higgs粒子的发现,接下来高能对撞机的主要任务为标准模型的精确检验以及新物理信号的寻找。电弱四规范耦合(QGCs)的测量对于标准模型规范结构的检验以及电弱对称性自发破缺机制的研究具有非常重要的意义,而三规范玻色子(TGB)产生过程与QGCs直接相关,因此本篇论文的研究重点为高能对撞机上TGB产生过程的精确研究。大型强子对撞机(LHC)上ZZW产生过程与四规范耦合W+W-ZZ直接相关,实验数据与标准模型预言的任何偏差都将意味着新物理的存在。而大额外维模型因为预言了TeV能标下的量子引力效应,所以在标准模型的诸多拓展中格外引入注目,因此我们研究了LHC上ZZW产生过程中可能的大额外维效应,并给出了精确到次领头阶QCD的结果。我们的结果表明该过程的NLO QCD修正非常明显,并且会显著压低领头阶的大额外维效应,因此我们认为领头阶结果高估了大额外维效应,为了给出可信的理论预言,NLO QCD修正是必须要考虑的。我们还发现NLO QCD修正和大额外维效应对末态粒子的相空间有很强的依赖,大额外维效应集中在高横动量(ZZ不变质量)和中心快度区域,因此采用合适的事例选择方案,大额外维效应可以被显著提高。与强子对撞机相比,正负电子对撞机背景非常干净,实验测量可以达到很高的精度,因此对相关可观测量给出尽可能精确的理论预言是十分必要的。e+e→W+W-γ过程对于四规范耦合顶点W+W-γγ和W+W-Zγ非常重要,我们计算了国际直线对撞机(ILC)上W+W-7产生截面的次领头阶电弱修正以及初态光子辐射(ISR)的重求和效应。通过分析ILC上W+W-γ产生截面随对撞机能量的变化,我们发现电弱修正明显压低了领头阶截面,并且高阶的ISR效应只在(?)处于阈值附近时比较明显,在对撞能量较高的区域几乎可以忽略不计。我们还给出了(?)=500 GeV时,产生截面对pTW-(r),yW-(r)和W玻色子对不变质量MWW的分布,发现电弱修正对末态粒子相空间有很强的依赖。最后我们采用传统的窄宽度近似法分析了W玻色子对的轻子衰变,结果表明末态光子和轻子在空间上可以很好地分开。本论文的成果总结如下：·本文首次在大额外维模型中研究了pp→ZZW±+X过程的NLO QCD修正,该过程的NLO QCD修正非常显著并且会大大压低领头阶大额外维效应。我们还发现ZZW产生过程的大额外维效应主要集中在末态粒子的高横动量和中心快度区域,选取合适的事例选择方案,大额外维效应可以被显著提高,这些结论为实验上寻找大额外维信号提供了一定的理论指导。·我们给出了ILC上e+e-→W+W-γ过程目前最精确的理论预言,计算了完整的NLO EW修正以及初态光子辐射(ISR)的重求和效应。结果表明该过程的EW修正对领头阶截面有明显的压低,而高阶ISR效应只在(?)处于闽值附近时非常显著,对撞能量较高时可以忽略不计。我们还研究了末态粒子的微分分布以及W玻色子的衰变,为实验上通过该过程测量四规范耦合提供了指导。·圈图计算中,我们遇到了小Gram矩阵行列式以及标量积分函数所导致的数值结果不稳定问题,为此我们进一步发展了计算圈图的程序LoopTools。其中小Gram矩阵行列式问题可以采用双精度和四精度混合计算的方案,在解决数值不稳定性的同时,保证计算效率,标量积分函数问题则需要对LoopTools的标量积分库做适当的修改。该问题的解决为实验室三体末态的精确计算奠定了基础。·实辐射计算中,相空间分割法不同部分之间的大数相消非常严重,为此我们采用误差收敛更快的双极点剪除方法来处理实辐射部分的红外发散,并且引入了参数α来控制剪除项的相空间大小,从而降低“missed-binning”问题发生的概率。
[Abstract]:The standard model is the most successful particle physics theory constructed so far. With the discovery of Higgs particles, the main tasks of the high energy collider are the accurate test of the standard model and the search for the new physical signals. The measurement of the electrical weak four gauge coupling (QGCs) for the standard model standard structure and the electrical weak symmetry The study of spontaneous breaking mechanism is of great significance, and the process of the three specification boson (TGB) generation is directly related to the QGCs. Therefore, the research of this paper is the precise study of the TGB production process on the high energy collider. The ZZW production process on the Large Hadron Collider (LHC) is directly related to the four specification coupling W+W-ZZ, the experimental data and the standard. Any deviation from the prediction of the quasi model will mean the existence of the new physics. The large external dimension model, which predicts the quantum gravitational effect of the TeV, makes a great deal of attention in the expansion of the standard model. Therefore, we have studied the possible large additional dimension effect in the process of ZZW production on LHC, and given the precision to the second leading order Q. CD results. Our results show that the NLO QCD correction of the process is very obvious and will significantly lower the large outer dimension effect of the leading order. Therefore, we think the leading order results overestimate the large external dimension effect. In order to give a credible theoretical prediction, the NLO QCD correction must be considered. We also found the NLO QCD correction and the large external dimension effect. There is a strong dependence on the phase space of the last state particles. The large external dimension effect is concentrated in the high transverse momentum (ZZ constant mass) and the center speed area. Therefore, the large external dimension effect can be greatly improved by using the appropriate case selection scheme. Compared with the Hadron Collider, the positive and negative electron collider has a very clean background and the experimental measurement can reach very high. High precision, therefore, it is very necessary for the.E+e to W+W- gamma process to predict the relevant observable measurements as accurately as possible. It is very important for the four standard coupling vertices W+W- gamma gamma and W+W-Z gamma. We calculated the second leading order electrical weak correction of the W+W-7 production cross section on the International Linear Collider (ILC) and the re seeking of the initial state photon radiation (ISR). And effect. By analyzing the changes in the energy of the W+W- gamma production section on the ILC, we find that the electrical weak correction significantly lowers the leading section, and the higher order ISR effect is obvious only when the threshold is near the threshold, and it is almost negligible in the region with high collision energy. We also give the (?) =500 GeV to produce a cross section. The distribution of pTW- (R), yW- (R) and W bosons for the invariant mass MWW is found to have strong dependence on the phase space of the final state particles. Finally, we use the traditional narrow width approximation method to analyze the lepton decay of the W boson pair. The results show that the final state of the photon and the lepton can be well separated in the space. The results of this paper are summarized as follows: In this paper, the NLO QCD correction of the PP to ZZW + +X process is studied for the first time in the large external dimension model. The NLO QCD correction of this process is very significant and will greatly reduce the large external dimension effect of the head order. We also find that the large outer dimensional effect of the ZZW production process is mainly concentrated in the high transverse momentum and central speed region of the final state particles, and the appropriate selection is selected. The case selection scheme, the large external dimension effect can be significantly improved, these conclusions provide some theoretical guidance for the large external dimension signal in the experiment. We give the most accurate theoretical predictions of the e+e- to W+W- gamma process on ILC, and calculate the complete NLO EW correction and the initial state photon radiation (ISR) re search and effect. It is clear that the EW correction of the process has an obvious low pressure on the leading section, while the high order ISR effect is very significant only when (?) near the min value. When the collision energy is high, the differential distribution of the final state particles and the decay of the W boson are also studied, which provides guidance for the measurement of the four gauge coupling in the experiment. In the calculation of loop graphs, we have encountered the problem of the numerical results instability caused by the determinant of small Gram matrix and the scalar integral function. Therefore, we further develop the program LoopTools. of the calculation circle graph, in which the problem of small Gram matrix determinant can be mixed with double precision and four precision, in solving the numerical instability. At the same time, the scalar integral function of scalar integral function should be modified properly to ensure the efficiency of the scalar integral function. The solution of the problem will lay the foundation for the accurate calculation of the final state of the laboratory. In the actual radiation calculation, the large number cancellation between the different parts of the phase space segmentation method is very serious, so we adopt the error convergence more. The fast double pole cutting method is used to deal with the infrared divergence of the real radiation part, and the parameter alpha is introduced to control the phase space of the cut item, thus reducing the probability of the "missed-binning" problem.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O572.214

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