Grand unified textures for neutrino and quark mixings

Nov, 1998
20 pages
Published in:
  • JHEP 03 (1999) 002
e-Print:
Report number:
  • DFAQ-98-TH-01,
  • FISIST-6-98-CFIF

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Abstract:
The atmospheric neutrino data imply large mixing between the νμ\nu_\mu and ντ\nu_\tau states, θ23=(45±12)\theta_{23} = (45\pm 12)^\circ, while the MSW solution to the solar neutrino problem needs very small mixing angle θ12=(2±1)\theta_{12} = (2\pm 1)^\circ. In the quark sector the situation is rather opposite -- the 23 mixing is tiny, θ232\theta_{23}\simeq 2^\circ, versus reasonable 12 mixing, θ1213\theta_{12}\simeq 13^\circ. We show that such complementary patterns of the quark and leptonic mixings could naturally emerge in the context of the SU(5) grand unification, assuming that the fermion mass matrices have the Fritzsch-like structures but their off-diagonal entries are not necessarily symmetric. Such a picture exhibits a `see-saw' like correspondence between the quark and leptonic mixing patterns so that the smaller the quark mixing angle is, the larger the corresponding leptonic mixing angle becomes. This fact simply follows from the fermion multiplet structure in SU(5). We also discuss a model with horizontal symmetry U(2) in which the discussed pattern of the mass matrices can arise rather naturally.
  • grand unified theory: SU(5)
  • neutrino: mixing angle
  • quark: mixing angle
  • fermion: mass
  • mass: texture
  • horizontal symmetry
  • numerical calculations: interpretation of experiments
  • bibliography