715 research outputs found
On the hierarchy of neutrino masses
We present a model of neutrino masses combining the seesaw mechanism and
strong Dirac mass hierarchy and at the same time exhibiting a significantly
reduced hierarchy at the level of active neutrino masses. The heavy Majorana
masses are assumed to be degenerate. The suppression of the hierarchy is due to
a symmetric and unitary operator R whose role is discussed. The model gives
realistic mixing and mass spectrum. The mixing of atmospheric neutrinos is
attributed to the charged lepton sector whereas the mixing of solar neutrinos
is due to the neutrino sector. Small U_e3 is a consequence of the model. The
masses of the active neutrinos are given by
and .Comment: 12 pages; Talk presented by M. Jezabek at 'Supersymmetry and Brane
Worlds,' Fifth European Meeting Planck 02, Kazimierz, Poland, May 25-29,
2002, to appear in Acta Phys. Polon.
Scale Setting in Top Quark Decays
We compute the QCD corrections to the Standard Model
decay as well as the non standard decay . We then use our results to compute the BLM scale for these decays, and
study the dependence of the BLM scale on the mass of the boson in the decay. We
find that the BLM procedure gives extremely small scales when top decays into
heavy bosons. When we try to improve the BLM scale by reexpressing rates as a
functions of the top quark running mass, we find the BLM scale exhibits
unnatural dependence on the boson mass, casting doubts on the applicability of
the BLM procedure to these processes.Comment: Uses REVTEX, 9 pages, 4 EPS figures embedded with epsf.sty Some
references and 1 figure added, conclusions slightly modified, numerical
results unchanged. Version accepted for publication in Physics Letters
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