Implications of the Quark Mass Hierarchy on Flavor Mixings

We stress that the observed pattern of flavor mixings can be partly interpreted by the quark mass hierarchy without the assumption of specific quark mass matrices. The quantitatively proper relations between the Kobayashi-Maskawa matrix elements and quark mass ratios, such as $$|V_{cb}| \approx |V_{ts}| \approx \sqrt{2} (\frac{m_s}{m_b} -\frac{m_c}{m_t}) [1 + 3 (\frac{m_s}{m_b} + \frac{m_c}{m_t} ) ],$$ are obtainable from a simple {\it Ansatz} of flavor permutation symmetry breaking at the weak scale. We prescribe the same {\it Ansatz} at the supersymmetric grand unified theory scale, and find that its all low-energy consequences on flavor mixings and $CP$ violation are in good agreement with current experimental data.Comment: Latex 19 pages including 5 PS figure

A Natural Supersymmetric Model with MeV Dark Matter

It has previously been proposed that annihilating dark matter particles with MeV-scale masses could be responsible for the flux of 511 keV photons observed from the region of the Galactic Bulge. The conventional wisdom, however, is that it is very challenging to construct a viable particle physics model containing MeV dark matter. In this letter, we challenge this conclusion by describing a simple and natural supersymmetric model in which the lightest supersymmetric particle naturally has a MeV-scale mass and the other phenomenological properties required to generate the 511 keV emission. In particular, the small ($\sim$ $10^{-5}$) effective couplings between dark matter and the Standard Model fermions required in this scenario naturally lead to radiative corrections that generate MeV-scale masses for both the dark matter candidate and the mediator particle.Comment: 4 pages, 1 figure. v2: Small modification to discussion of spectru