Matter-antimatter Asymmetry In Left-right Symmetric Model

The origin of matter-antimatter asymmetry is one of the most challenging prob-lems in elementary particle physics and cosmology. To produce baryon number from aB = 0 universe, we need a dynamical mechanism to produce baryon asymmetry in theevolvement of the universe. Baryogenesis via Leptogenesis is such a dynamical mech-anism of producing baryon asymmetry and has gained significant attention since thediscovery of non-zero neutrino masses. In this thesis, we study the lepton mixing an-gles and leptogenesis in the left-right symmetric model. By considering quark and lep-ton symmetry mD～mu and quark-lepton complementarity relations:θ₁₂ +θ₁₂^q≈45°andθ₂₃ +θ₂₃^q≈45°, we assume the bi-maximal mixing matrix existing charged lep-ton sector and UCKM existing in neutrino sector. With this assumption, lepton mixingmatrix with 2-3 near maximal, 1-2 large and 1-3 small mixing is obtained. Then, wediscuss several sources of CP-asymmetry in right-handed neutrino decay, thereinto, anew radiative correction diagram involving right-handed triplet Higgs are introduced,which can make large contribution to the total CP-asymmetry.We also propose S4 flavor symmetry based on the supersymmetric SU(5) grandunified model. In this model, fermions are assigned to S4 anti-symmetric representation32. The fermion masses are from the Yukawa couplings involving Higgs multipletsbelonging to SU(5) representations 1, 5, 5 and 45, and the structures of mass matricesare determined by the S4 flavor symmetry. We introduce right-handed neutrinos, andthen light neutrino masses purely come from the type-I seesaw mechanism. Aftersymmetry broken, we obtained the fermion mass matrices containing parameters whichare less than the input values. The numerical results of fermion masses and mixingmatrices are in accord with the experimental results.At last, we discuss the baryogenesis in a new extended left-right symmetric grandunified model with SO(3) flavor symmetry. In this model, new isospin SU(2) groupand new superheavy fermions as mirrors of low energy fermions are introduced. TheDirac-type Yukawa couplings of neutrinos are too small, so that the CP-asymmetry produced by the decay of right-handed neutrinos are not large enough to produce suf-ficient baryon-asymmetry. Then, decays of superheavy gauge boson are introduced toproduce B - L and CP violation. At the electroweak scale, B - L violation is trans-ferred to baryon violation through Sphaleron process, and we get the baryon asymme-try which is in accord with present universe observation.