Flavor-changing axions and Dirac neutrino masses

Implementing the axion concept in the context of 3-3-1 extensions of the Standard Model leads to richer properties than in the simpler axion setups, and they are related to the Dirac neutrino seesaw mechanism. In this way, the smallness of neutrino masses, the strong <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>C</a:mi><a:mi>P</a:mi></a:mrow></a:math> problem, the nature of dark matter, and the number of families all have a common origin. Besides having an enhanced coupling to photons, our revamped axion can also be distinguished from both Dine-Fischler-Srednicki-Zhitnisky and Kim-Shifman-Vainshtein-Zakharov axions through its couplings to fermions. The latter lead to interesting phenomenological consequences, including flavor-changing axion-emitting two-body <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>K</c:mi></c:math>, <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>B</e:mi></e:math>, and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>D</g:mi></g:math> meson decays.