Summary of the PhD thesis: Construction and investigation of a neutrino mass model with A4 flavour symmetry by pertubation method

The thesis is devoted to constructing and evaluating versions of the SM extended with an A4 symmetry to explain some of the problems of neutrino physics. Within these extended models, the results on neutrino masses and mixing, derived by the perturbation method, are very closed to the global fit. In two models, a relation between the Dirac CPV phase and the mixing angles is established. In particular, the models predict Dirac CPV phase δCP and effective mass of neutrinoless double beta decay jhmeeij in good agreement with the current experimental data.
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Summary of the PhD thesis: Construction and investigation of a neutrino mass model with A4 flavour symmetry by pertubation method MINISTRY OF EDUCATION VIETNAM ACADEMY AND TRAINING OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY ……..….***………… PHI QUANG VAN CONSTRUCTION AND INVESTIGATION OF ANEUTRINO MASS MODEL WITH A4 FLAVOUR SYMMETRY BY PERTUBATION METHOD Speciality: Theoretical and mathematical physics Code: 62 44 01 03 SUMMARY OF THE PHD THESIS Hanoi – 2017 This thesis was compled at the Graduate University Science and Technology, Viet Nam Academy of Science and Technology.Supervisors: Assoc. Prof. Dr. Nguyen Anh KyInstitute of Physics, Viet Nam Academy of S cience and Technology.Referee 1: Prof. Dr. Dang Van SoaReferee 2: Assoc. Prof. Dr. Nguyen Ai VietReferee 3: Dr. Tran Minh HieuThis dissertation will be defended in front of the evaluating assemblyat academy level, Place of defending: meeting room, GraduateUniversity Science and Technology, Viet Nam Academy of Scienceand Technology.This thesis can be studied at:- The Vietnam National Library- Library of the National Academy of Public AdministrationIntroductionMotivation of thesis topicNeutrino masses and oscillations are always a challenge in elementary particle physics.We have seen in the standard model (SM) that neutrinos do not have mass, but theexperiment has shown that neutrinos have mass. The problem of neutrino massesand mixings is among the problems beyond the SM. This problem is important for notonly particle physics but also nuclear physics, astrophysics and cosmology, therefore,it has attracted much interest. At present, there are many standard model extensionsto studying neutrino masses and oscillations: the supersymmetry model, the grandunified theory, the left-right symmetry model, the 3-3-1 model, the mirror symmetrymodel, Zee model, Zee-Babu model, the flavour symmetry model, etc. One of the standard model extentions to explain neutrino mass is to add a flavorsymmetry to the SM symmetry, such as SU (3)C × SU (2)L × U (1)Y × GF , in whichGF is a flavour symmetry group, for example S3 , S4 , A4 , A5 , T 7, ∆(27) [1],... A popularflavour symmetry intensively investigated in the literature is that described by thegroup A4 (see, for instance, [2, 3]) allowing obtaining a tribi-maximal (TBM) neutrinomixing corresponding to the mixing angles θ12 ≈ 35.26◦ (sin2 θ12 = 1/3), θ13 = 0◦ andθ23 = 45◦ . The recent experimental data that showing a non-zero mixing angle θ13and a possible non-zero Dirac CP-violation (CPV) phase δCP , rejects, however, theTBM scheme [4, 5]. There have been many attempts to explain these experimentalphenomena. In particular, for this purpose, various models with a discrete flavoursymmetry [1], including an A4 flavor symmetry, have been suggested [1–3].The objectives of the thesisThe thesis is devoted to constructing and evaluating versions of the SM extendedwith an A4 symmetry to explain some of the problems of neutrino physics. Withinthese extended models, the results on neutrino masses and mixing, derived by theperturbation method, are very closed to the global fit [4, 5]. In two models, a relationbetween the Dirac CPV phase and the mixing angles is established. In particular, themodels predict Dirac CPV phase δCP and effective mass of neutrinoless double betadecay |hmee i| in good agreement with the current experimental data. 1 IntroductionThe main contents of the thesisIn general, the models, based on A4 flavour symmetry, have extended lepton and scalarsectors containing new fields in additions to the SM ones which now may have an A4symmetry structure. Therefore, base on an A4 flavour symmetry, these fields may alsotransform under A4 . At the beginning, the A4 based models were build to describe aTBM neutrino mixing (see, for example, [2]) but later many attempts, such as thosein [1, 3, 6], to find a model fitting the non-TBM phenomenology, have been made. Onthese models, however, are often imposed some assumptions, for example, the vacuumexpectation values (VEV’s) of some of the fields, especially those generating neutrinomasses, have a particular alignment. These assumptions may lead to a simpler diag-onalization of a mass matrix but restrict the generality of the model. Since, accordingto the current experimental data, the discrepancy of a p ...