Theµ-τreflection symmetry of Majorana neutrinos.

The observed pattern of lepton flavor mixing and CP violation strongly indicates the possible existence of a simple flavor symmetry in the neutrino sector-the effective Majorana neutrino mass term keeps invariant when the three left-handed neutrino fields transform asνeL→(νeL)c,νµL→(ντL)candντL→(νµL)c. A direct application of such aµ-τreflection symmetry to the canonical seesaw mechanism can help a lot to constrain the flavor textures of active and sterile Majorana neutrinos. The present article is intended to summarize the latest progress made in exploring the properties of this minimal flavor symmetry, its translational and rotational extensions, its soft breaking effects via radiative corrections from a superhigh energy scale to the electroweak scale, and its various phenomenological implications.

The minimal seesaw and leptogenesis models.

Given its briefness and predictability, the minimal seesaw-a simplified version of the canonical seesaw mechanism with only two right-handed neutrino fields-has been studied in depth and from many perspectives, and now it is being pushed close to a position of directly facing experimental tests. This article is intended to provide an up-to-date review of various phenomenological aspects of the minimal seesaw and its associated leptogenesis mechanism in neutrino physics and cosmology. Our focus is on possible flavor structures of such benchmark seesaw and leptogenesis scenarios and confronting their predictions with current neutrino oscillation data and cosmological observations. In this connection particular attention will be paid to the topics of lepton number violation, lepton flavor violation, discrete flavor symmetries, CP violation and antimatter of the Universe.

A review of µ-τ flavor symmetry in neutrino physics.

Behind the observed pattern of lepton flavor mixing is a partial or approximate µ-τ flavor symmetry-a milestone on our road to the true origin of neutrino masses and flavor structures. In this review article we first describe the features of µ-τ permutation and reflection symmetries, and then explore their various consequences on model building and neutrino phenomenology. We pay particular attention to soft µ-τ symmetry breaking, which is crucial for our deeper understanding of the fine effects of flavor mixing and CP violation.