费米子的反常电弱耦合在对撞机上的探测

发布时间：2018-03-21 12:07

本文选题：标准模型　切入点：有效场论　出处：《清华大学》2016年博士论文　论文类型：学位论文

【摘要】：基于有效场论思想的有效拉氏量方法是一种模型无关的探索超出标准模型的新物理的方法。通过有效拉氏量中高维有效算符的系数,也即所谓的反常耦合,可以将新物理在低能下的效应参数化。已有的关于反常耦合的研究,主要集中在Higgs和规范玻色子相关的部分,而很少涉及到费米子。本文主要研究费米子的反常电弱耦合,利用所有由费米子和电弱规范玻色子构建的、满足标准模型S U(3)c×S U(2)L×U(1)Y对称性的、CP守恒的6维算符,我们计算了费米子的反常电弱耦合对于不同过程、尤其是高能对撞机上的过程的影响。我们认为这项工作是对反常耦合研究的一个非常重要的补充和扩展。对于轻子的反常耦合,我们首先研究了已有的电弱精确测量相关的实验对反常耦合的约束,包括LEP上的e~+e~-→W~+W~-过程截面以及W和Z的轻子衰变的宽度等随反常耦合的变化,在假定反常耦合引起的偏差不会大于5%的条件下,现有的实验结果可以给出O(0.1-1)TeV-2量级的约束。我们还进一步研究了未来的高能正负电子对撞机,即√s=500 GeV和√s=1 TeV的ILC探测反常耦合的能力,通过分析e~+e~-→W~+W~-过程截面关于末态W的出射角度θ的分布,找到了能够提高探测反常耦合精度的cosθ截断,最终在同样假定5%偏差的条件下,得到了对反常耦合的O(0.01-0.1)TeV-2量级的约束。对于夸克的反常耦合,我们主要研究了8 TeV和14 TeV的LHC实验能够给出的约束。我们计算了8 TeV和14 TeV的LHC上的pp→W~+W~-过程、以及作为补充的pp→ZZ/Zγ/γγ过程的截面随反常耦合的变化,通过分析反常信号的运动学分布,找到了一系列能够提高探测精度的运动学截断,在假定偏差不超过20%的条件下最终得到了对反常耦合的O(0.1-1)TeV-2量级的约束。我们在计算中发现了反常顶角之间的相消效应,为了避免这一效应导致的探测精度的降低,我们进一步考虑了一类只包含反常三线顶角的过程,如pp→W*→lν和pp→Z*/γ*→l+l-,利用这一过程得到的约束比pp→W~+W~-这类过程提高了1到2个量级。我们还简单的讨论了如何区分不同反常耦合的效应,并引入χ2函数具体计算了不同反常耦合在运动学分布上的不同。
[Abstract]:The effective Lagrangian method based on the theory of effective field theory is a model-independent method for exploring new physics beyond the standard model. By means of the coefficients of the high-dimensional effective operators in the effective Lagrangian, that is, the so-called anomalous coupling, It is possible to parameterize the effects of the new physics at low energy. The existing studies on anomalous coupling are mainly focused on the parts of Higgs and gauge bosons, but seldom on fermions. In this paper, the anomalous weak coupling of fermions is studied. Using all the six dimensional operators of CP conservation constructed from fermions and electrically weak gauge bosons that satisfy the standard model S U ~ (3) C 脳 U ~ (2) U ~ (2 +) L 脳 U ~ (1) Y symmetry, we calculate the anomalous weak coupling processes of fermions for different processes. Especially the influence of the process on the high-energy collider. We think this work is a very important supplement and extension to the anomalous coupling research. We first study the constraints on anomalous coupling by existing experiments related to the measurement of electrical weakly precise measurements, including the ewe on LEP. 鈫扷nder the assumption that the deviations caused by anomalous coupling are not greater than 5%, the variation of the cross section and the width of the lepton decay of W and Z with anomalous coupling is assumed. The existing experimental results can give the constraints of the order of O _ (0.1) ~ (-1) TeV ~ (-2). We have also further studied the ability of the future high-energy positron collider, that is, the ILC of #number0# GeV and 1 TeV, to detect anomalous coupling. 鈫扵he distribution of the exit angle 胃 of the cross section of the WW ~ (-) process with respect to the final state W is found, and the cos 胃 truncation which can improve the detection accuracy of anomalous coupling is found. Finally, under the same assumption of 5% deviation, In this paper, we obtain the constraints of order of magnitude 0. 01-0. 1 of TeV-2 for anomalous coupling. For the anomalous coupling of quarks, we mainly study the constraints that can be given in the LHC experiments of 8 TeV and 14 TeV. We calculate the pp on LHC of 8 TeV and 14 TeV. 鈫扺 ~ WN-process, and the pp as a complement. 鈫扵he cross-section of ZZ/Z 纬 / 纬纬 process changes with anomalous coupling. By analyzing the kinematic distribution of anomalous signals, a series of kinematic truncations are found to improve the detection accuracy. Under the assumption that the deviation is no more than 20%, we finally obtain the constraint of the order of 0. 1-1 / 1 TeV-2 for anomalous coupling. In order to avoid the decrease of detection accuracy caused by this effect, we have found the elimination effect between abnormal vertices. We further consider a class of processes that contain only anomalous three-wire vertices, such as pp. 鈫扺 *. 鈫扸 and pp. 鈫抁ang / 纬 *. 鈫扡 l l, the constraints obtained by using this process are higher than pp. 鈫扺e also briefly discuss how to distinguish the effects of different anomalous coupling, and introduce 蠂 2 function to calculate the difference of kinematic distribution of different anomalous coupling.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O572.2

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