Why is the 3×3 Neutrino Mixing Matrix Almost Unitary in Realistic Seesaw Models?

  • A simple extension of the standard model is to introduce n heavy right-handed Majorana neutrinos and preserve its SU(2)L \times U(1)Y gauge symmetry. Diagonalizing the (3+n)×(3+n) neutrino mass matrix, we obtain an exact analytical expression for the effective mass matrix of νe, νμand ντ. It turns out that the 3×3 neutrino mixing matrix V, which appears in the leptonic charged-current weak interactions, must not be exactly unitary. The unitarity violation of V is negligibly tiny, however, if the canonical seesaw mechanism works to reproduce the correct mass scale of light Majorana neutrinos. A similar conclusion can be drawn in the realistic Type-Ⅱ seesaw models.
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XING Zhi-Zhong and ZHOU Shun. Why is the 3×3 Neutrino Mixing Matrix Almost Unitary in Realistic Seesaw Models?[J]. Chinese Physics C, 2006, 30(9): 828-832.
XING Zhi-Zhong and ZHOU Shun. Why is the 3×3 Neutrino Mixing Matrix Almost Unitary in Realistic Seesaw Models?[J]. Chinese Physics C, 2006, 30(9): 828-832. shu
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Received: 2006-03-23
Revised: 1900-01-01
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Why is the 3×3 Neutrino Mixing Matrix Almost Unitary in Realistic Seesaw Models?

    Corresponding author: ZHOU Shun,
  • Institute of High Energy Physics, CAS, Beijing 100049, China

Abstract: A simple extension of the standard model is to introduce n heavy right-handed Majorana neutrinos and preserve its SU(2)L \times U(1)Y gauge symmetry. Diagonalizing the (3+n)×(3+n) neutrino mass matrix, we obtain an exact analytical expression for the effective mass matrix of νe, νμand ντ. It turns out that the 3×3 neutrino mixing matrix V, which appears in the leptonic charged-current weak interactions, must not be exactly unitary. The unitarity violation of V is negligibly tiny, however, if the canonical seesaw mechanism works to reproduce the correct mass scale of light Majorana neutrinos. A similar conclusion can be drawn in the realistic Type-Ⅱ seesaw models.

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