Undemocratic Dirac seesaw

The standard model left-handed neutrinos and several right-handed neutrinos can obtain a tiny Dirac mass matrix through their mixings with relatively heavy Dirac fermions. In this Dirac seesaw scenario, the mixings involving the left-handed neutrinos can be allowed much larger than those involving the right-handed neutrinos. This undemocratic parameter choice is attractive to phenomenology. We show that the small mixings between the heavy Dirac fermions and the right-handed neutrinos can have a common origin with the observed baryon asymmetry in the universe. We also connect the introduction of right-handed neutrinos to the existence and stability of dark matter by a new $U(1)$ gauge symmetry for dark photon or baryon-minus-lepton number. We then specify how to embed our scenario into a left-right symmetric theory or a grand unification theory.Comment: 6 pages, 2 figure

4-(1H-Tetra­zol-5-yl)-1H-indole

There are two mol­ecules with similar configurations in the asymmetric unit of the title compound, C9H7N5, which are linked by inter­molecular N—H⋯N hydrogen bonds into chains with graph-set motif C 2 2(8) along the b axis. The indole core has the expected planar geometry in the two mol­ecules, with a maximum deviation of 0.008 (8) Å from the least-squares plane defined by the nine constituent atoms, and the dihedral angles between the indole and tetra­zole rings are similar [42.4 (2) and 42.7 (2)°]