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Register a new user$mu-tau$ Reflection Symmetry in in Lepton Mixing and Radiatively Generated Leptogenesis
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We study a $mu - tau$ reflection symmetry in neutrino sector realized at the GUT scale in the context of the seesaw model. In our scenario, the exact $mu - tau$ reflection symmetry realized in the basis where the charged lepton and heavy Majorana mass matrices are diagonal, leads to vanishing lepton asymmetries. We find that, in the minimal supersymmetry extension of the seesaw model with appropriate values of $tanbeta$, the renormalization group (RG) evolution from the GUT scale to seesaw scale can induce a successful leptogenesis. It is shown that the right amount of the baryon asymmetries $eta_B$ can be achieved via so-called resonant leptogenesis, which can be realized at rather low seesaw scale in our scenario, so that the well-known gravitino problem is safely avoided. In this work, we consider both flavor dependent and flavor independent leptogenesis, and demonstrate how they lead to different amounts of baryon asymmetries in detail.
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We study the consequences of the $Z_2$-symmetry behind the $mu$--$tau$ universality in neutrino mass matrix. We then implement this symmetry in the type-I seesaw mechanism and show how it can accommodate all sorts of lepton mass hierarchies and generate enough lepton asymmetry to interpret the observed baryon asymmetry in the universe. We also show how a specific form of a high-scale perturbation is kept when translated via the seesaw into the low scale domain, where it can accommodate the neutrino mixing data. We finally present a realization of the high scale perturbed texture through addition of matter and extra exact symmetries.
We consider an exact mu-tau reflection symmetry in neutrino sectorrealized at the GUT scale in the context of the seesaw model with and without supersymmetry. Assuming the two lighter heavy Majorana neutrinos are degenerate at the GUT scale, it is shown that the renormalization group (RG) evolution from the GUT scale to the seesaw scale gives rise to breaking of the mu-tau symmetry and a tiny splitting between two degenerate heavy Majorana neutrino masses as well as small variations of the CP phases in Y_nu, which are essential to achieve a successful leptogenesis. Such small RG effects lead to tiny deviations of theta_{23} from the maximal value and the CP phase delta_{CP} from pi/2 imposed at the GUT scale due to mu-tau reflection symmetry. In our scenario, the required amount of the baryon asymmetry eta_B can be generated via so-called resonant e-leptogenesis, in which the wash-out factor concerned with electron flavor plays a crucial role in reproducing a successful leptogenesis. We show that CP violation responsible for the generation of baryon asymmetry of our universe can be directly linked with CP violation measurable through neutrino oscillation as well as neutrino mixing angles theta_{12} and theta_{13}. We expect that, in addition to the reactor and long baseline neutrino experiments, the measurements for the supersymmetric parameter tan{beta} at future collider experiments would serve as an indirect test of our scenario of baryogenesis based on the mu-tau reflection symmetry.
We investigate the consequences of $mu-tau$ reflection symmetry in presence of a light sterile neutrino for the $3+1$ neutrino mixing scheme. We discuss the implications of total $mu-tau$ reflection symmetry as well partial $mu-tau$ reflection symmetry. For the total $mu-tau$ reflection symmetry we find values of $theta_{23}$ and $delta$ remains confined near $pi/4$ and $pm pi/2$ respectively. The current allowed region for $theta_{23}$ and $delta$ in case of inverted hierarchy lies outside the area preferred by the total $mu-tau$ reflection symmetry. However, interesting predictions on the neutrino mixing angles and Dirac CP violating phases are obtained considering partial $mu-tau$ reflection symmetry. We obtain predictive correlations between the neutrino mixing angle $theta_{23}$ and Dirac CP phase $delta$ and study the testability of these correlations at the future long baseline experiment DUNE. We find that while the imposition of $mu-tau$ reflection symmetry in the first column admit both normal and inverted neutrino mass hierarchy, demanding $mu-tau$ reflection symmetry for the second column excludes the inverted hierarchy. Interestingly, the sterile mixing angle $theta_{34}$ gets tightly constrained considering the $mu-tau$ reflection symmetry in the fourth column. We also study consequences of $mu-tau$ reflection symmetry for the Majorana phases and neutrinoless double beta decay.
We embed $mu-tau$ reflection symmetry into the minimal seesaw formalism, where two right-handed neutrinos are added to the Standard Model of particle physics. Assuming that both the left- and right-handed neutrino fields transform under $mu-tau$ reflection symmetry, we obtain the required forms of the neutrino Dirac mass matrix and the Majorana mass matrix for the right-handed neutrinos. To investigate the neutrino phenomenology at low energies, we first consider the breaking of $mu-tau$ reflection symmetry due to the renormalization group running, and then systematically study various breaking schemes by introducing explicit breaking terms at high energies.
Nonstandard interactions (NSIs), possible subleading effects originating from new physics beyond the Standard Model, may affect the propagation of neutrinos and eventually contribute to measurements of neutrino oscillations. Besides this, $ mu-tau $ reflection symmetry, naturally predicted by non-Abelian discrete flavor symmetries, has been very successful in explaining the observed leptonic mixing patterns. In this work, we study the combined effect of both. We present an $S_4$ flavor model with $mu-tau$ reflection symmetry realized in both neutrino masses and NSIs. Under this formalism, we perform a detailed study for the upcoming neutrino experiments DUNE and T2HK. Our simulation results show that under the $mu-tau $ reflection symmetry, NSI parameters are further constrained and the mass ordering sensitivity is less affected by the presence of NSIs.
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