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Michael A. Schmidt

Publications and source records attributed to Michael A. Schmidt.

74 records · Page 5Linked to original sources

Quark lepton complementarity and renormalization group effects

We consider a scenario for the Quark-Lepton Complementarity relations between mixing angles in which the bi-maximal mixing follows from the neutrino mass matrix. According to this scenario in the lowest order the angle θ_{12} is \sim 1σ(1.5 - 2^\circ) above the best fit point coinciding practically with the tri-bimaximal mixing prediction. Realization of this scenario in the context of the seesaw type-I mechanism with leptonic Dirac mass matrices approximately equal to the quark mass matrices is studied. We calculate the renormalization group corrections to θ_{12} as well as to θ_{13} in the standard model (SM) and minimal supersymmetric standard model (MSSM). We find that in large part of the parameter space corrections Δθ_{12} are small or negligible. In the MSSM version of the scenario the correction Δθ_{12} is in general positive. Small negative corrections appear in the case of an inverted mass hierarchy and opposite CP parities of ν_1 and ν_2 when leading contributions to θ_{12} running are strongly suppressed. The corrections are negative in the SM version in a large part of the parameter space for values of the relative CP phase of ν_1 and ν_2: ϕ> π/2.

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Screening of Dirac flavor structure in the seesaw and neutrino mixing

We consider the mechanism of screening of the Dirac flavor structure in the context of the double seesaw mechanism. As a consequence of screening, the structure of the light neutrino mass matrix, m_ν, is determined essentially by the structure of the (Majorana) mass matrix, M_S, of new super-heavy (Planck scale) neutral fermions S. We calculate effects of the renormalization group running in order to investigate the stability of the screening mechanism with respect to radiative corrections. We find that screening is stable in the supersymmetric case, whereas in the standard model it is unstable for certain structures of M_S. The screening mechanism allows us to reconcile the (approximate) quark-lepton symmetry and the strong difference of the mixing patterns in the quark and lepton sectors. It opens new possibilities to explain a quasi-degenerate neutrino mass spectrum, special ``neutrino'' symmetries and quark-lepton complementarity. Screening can emerge from certain flavor symmetries or Grand Unification.

hep-ph↗