The number of sufficient and necessary conditions for CP conservation with Majorana neutrinos: three or four?

Abstract

As is well-known, there exist totally three CP-violating phases in the leptonic sector if three ordinary neutrinos are massive Majorana particles. In this short note, we raise the question whether the number of sufficient and necessary conditions for CP conservation in the leptonic sector with massive Majorana neutrinos is three or four. An intuitive answer to this question would be three, which is also the total number of independent CP-violating phases. However, we give a counter example, in which three conditions are in general not sufficient for CP conservation. Only for all the lepton masses and mixing angles within their experimentally allowed ranges can we demonstrate that it is possible to find out three weak-basis invariants, which should be vanishing to guarantee leptonic CP conservation.

15 pages, 4 figures, expressions improved, numerical mistakes about $m_{\ast }$ corrected, main conclusions unchanged. $m_{\ast }$ still has the meaning of critical mass, different from the comments made in Physics Letters B 821 (2021) 136635

References in corpus (3)

• Neutrino Masses, Lepton Flavor Mixing and Leptogenesis in the Minimal Seesaw Model
• Supersymmetric Jarlskog Invariants: the Neutrino Sector
• Sufficient and Necessary Conditions for CP Conservation in the Case of Degenerate Majorana Neutrino Masses

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• CP violation and flavor invariants in the seesaw effective field theory
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