122 research outputs found
A Domino Theory of Flavor
We argue that the fermion masses and mixings are organized in a specific
pattern. The approximately equal hierarchies between successive generations,
the sizes of the mixing angles, the heaviness of just the top quark, and the
approximate down-lepton equality can all be accommodated by many flavor models
but can appear ad hoc. We present a simple, predictive mechanism to explain
these patterns. All generations are treated democratically and the flavor
symmetries are broken collectively by only two allowed couplings in
flavor-space, a vector and matrix, with arbitrary O(1) entries. Repeated use of
these flavor symmetry breaking spurions radiatively generates the Yukawa
couplings with a natural hierarchy. We demonstrate this idea with two models in
a split supersymmetric grand unified framework, with minimal additional
particle content at the unification scale. Although flavor is generated at the
GUT scale, there are several potentially testable predictions. In our minimal
model the usual prediction of exact b-tau unification is replaced by the SU(5)
breaking relation m_tau / m_b = 3 / 2, in better agreement with observations.
Other SU(5) breaking effects in the fermion masses can easily arise directly
from the flavor model itself. The symmetry breaking that triggers the
generation of flavor necessarily gives rise to an axion, solving the strong CP
problem. These theories contain long-lived particles whose decays could give
striking signatures at the LHC and may solve the primordial Lithium problems.
These models also give novel proton decay signatures which can be probed by the
next generation of experiments. Measurement of the various proton decay
channels directly probes the flavor symmetry breaking couplings. In this
scenario the Higgs mass is predicted to lie in a range near 150 GeV.Comment: 33 pages, 11 figures, 5 tables. v2: Refs added, version to appear in
PR
Axion Isocurvature and Magnetic Monopoles
We propose a simple mechanism to suppress axion isocurvature fluctuations
using hidden sector magnetic monopoles. This allows for the Peccei-Quinn scale
to be of order the unification scale consistently with high scale inflation.Comment: 13 page
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