## Abstract

We study the neutrino mixing matrix (the MNS matrix) in the seesaw model. By assuming a large mass hierarchy for the heavy right-handed Majorana mass, we show that, in the diagonal Majorana base, the MNS matrix is determined by a unitary matrix, S, which transforms the neutrino Yukawa matrix, y_{ν}, into a triangular form, yΔ. The mixing matrix of light leptons is V_{KM}-S^{′}*, where V_{KM} ≡ V_{Le}^{†}V_{Lν} and S^{′}* ≡ V_{Lν}^{†}S*. Large mixing may occur without fine tuning of the matrix elements of yΔ even if the usual KM-like matrix V_{KM} is given by V_{KM} = 1. This large mixing naturally may satisfy the experimental lower bound of the mixing implied by the atmospheric neutrino oscillation.

Original language | English |
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Pages (from-to) | 379-391 |

Number of pages | 13 |

Journal | Progress of Theoretical Physics |

Volume | 103 |

Issue number | 2 |

DOIs | |

Publication status | Published - Feb 2000 |

Externally published | Yes |