Research On Models Of Neutrino Oscillation

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,v?,v?.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.