【作者】 王晓燕；

【导师】 陈相君；

【作者基本信息】 哈尔滨工业大学 ， 物理学， 2021， 博士

【摘要】 中微子振荡现象的发现是近几十年来最伟大的粒子物理成果之一,因为它证实中微子具有质量和混合,这意味着标准模型需要修改或者扩大。本文在以前研究成果的基础上进一步研究中微子振荡现象的各个方面,并且试图解开中微子振荡的来源问题。本文首先研究了中微子振荡的统计规律。运用量子随机理论,我们给出了中微子味态概率分布随时间演化公式,该公式表明中微子振荡是一个近似的马尔科夫过程。运用CTRW(连续时间随机行走)方法,我们给出了齐次离散型马尔科夫随机模型。通过模型模拟,我们推断太阳中微子和宇宙射线中微子在地球表面的味态分布都是三重最大的平衡味态概率分布。本文还给出了 一个中微子混合模式,该模式通过对Democratic质量矩阵引入微扰得到。根据右手中微子的弱超荷为0即轻子数为0,我们认识到右手中微子无法识别味态,因此我们假设右手中微子可以无差别的耦合三种中微子味态ve,vμ,vτ。结合Dominance假说,我们给出了 Democratic质量矩阵。加入Koide微扰参数化质量矩阵,通过研究参数对中微子混合的影响,我们给出了符合实验数据的中微子混合。本文还给出了中微子振荡CP不对称来源的一种设想。我们假设中微子振荡的CP不对称来源于Majorana右手中微子混合的CP相位。我们以TBM矩阵作为中微子混合的0级近似,把包含CP相位的右手中微子混合矩阵作为干扰矩阵,通过跷跷板机制对TBM中微子混合做出轻微的修正,使得中微子混合具有非0反应堆混合角以及CP相位。通过研究右手中微子衰变引起的轻子生成,我们给出了 CP相位角的范围。最后,本文还给出了一个从全新的角度解释中微子振荡来源的理论,该理论的中微子质量态和味态是一致的,因此避开了额外的中微子质量态,后者至今未找到。这个理论假设中微子味态转换是由右手中微子部的横向相互作用通过跷跷板机制诱导产生的,而中微子振荡是所有中微子味态变换相互作用达到平衡(即中微子味态分布达到平衡分布)之前的宏观现象,从而导致表观的中微子混乱模式。类似Yanagida(柳田勉)横向对称模型,我们在标准模型中引进大质量右手中微子,但是只在右手中微子部施加一个额外的横向对称。这样,我们给出了一个可以实现理论的模型。更多还原

【Abstract】 The discovery of neutrino oscillations is one of the greatest achievements of particle physics in recent decades,for it confirms neutrino mass and mixing,which implies that the standard model should be modified or expanded.Based on the previous researches,this dissertation further studies various aspects of neutrino oscillation and attempts to reveal the origin of neutrino oscillation.In this dissertation,statistical law of neutrino oscillation is studied.Using quantum stochastic theory,we give time-evolution formula of neutrino flavor distribution,which shows that neutrino oscillation is approximate Markoffian process.Using the CTRW(continuous-time random walk)method,we give the homogeneous time-discrete Markoffian random model.By model simulation,we infer that the flavor distributions of solar neutrino and cosmic ray neutrino on the earth’s surface are both three-fold maximum equilibrium distributions.We also present a neutrino mixing pattern,which is obtained by introducing perturbation to Democratic mass matrix.For the hypercharge of right-handed neutrino is 0,which means lepton-number is 0,we realize that right-handed neutrino cannot recognize flavor state of neutrino,thus we assume that right-handed neutrino can indiscriminately couple three neutrino flavor states ve,vμ,vτ.Combined with the Dominance hypothesis,we give Democratic mass matrix.Adding Koide perturbations and parameterizing mass matrix,by studying the relation of parameters and neutrino mixing,we give a neutrino mixing which matching experimental data.A scenario about source of CP asymmetry of neutrino oscillation is also presented in this dissertation.We assume that CP asymmetry of neutrino oscillation is derived from CP phase of Majorana right-handed neutrino mixing.We take the TBM matrix as zeroorder neutrino mixing,and right-handed neutrino mixing matrix containing CP phase as perturbation matrix.Through seesaw mechanism,slight modifications are made to TBM matrix with non-zero reactor mixing angle and CP phase.By studying Leptogenesis due to right-handed neutrino decay,we give the range of CP phase angle.At the end,this dissertation presents a new theory to explain source of neutrino oscillation,in which neutrino mass state is consistent to flavor state and extra neutrino mass state is avoided which has not been found yet.This theory assumes that neutrino flavor transformation results from horizontal interaction between right-handed neutrinos by seesaw mechanism,and neutrino oscillation is macro phenomenon before all neutrino flavor interactions arriving at balance(which means that neutrino flavor distribution arrives at equilibrium distribution),resulting in apparent pattern of neutrino chaos.By analogy with Yanagida horizontal extension,we introduce right-handed neutrino of large mass into the standard model(SM),while exert horizontal symmetry only on right-handed neutrino sector.Thus we present a model which can implement the theory.更多还原