83 research outputs found
Factoring the Strong CP Problem
We present a new mechanism to solve the strong CP problem using
axions, each dynamically relaxing part of the parameter. At high
energies the group becomes the diagonal
subgroup of an gauge group, and the non-perturbative effects in
each individual factor generate a potential for the corresponding
axion. The vacuum is naturally aligned to ensure at low
energies, and the masses of these axions can be much larger than for the
standard QCD axion. This mechanism avoids the introduction of a discrete
symmetry and associated 'mirror' copies of the SM fermions, and also avoids the
introduction and stabilization of new light colored states to modify the
running of the QCD gauge coupling found in other heavy axion models. This
strengthens the motivation for axion-like particles solving the strong CP
problem at points beyond the standard QCD axion curve in the
plane.Comment: 14 pages, 5 figure
Clockwork Axions in Cosmology: Is Chromonatural Inflation Chrononatural?
Many cosmological models rely on large couplings of axions to gauge fields.
Examples include theories of magnetogenesis, inflation on a steep potential,
chiral gravitational waves, and chromonatural inflation. Such theories require
a mismatch between the axion field range and the mass scale appearing in the coupling. This mismatch suggests an underlying monodromy, with
the axion winding around its fundamental period a large number of times. We
investigate the extent to which this integer can be explained as a product of
smaller integers in a UV completion: in the parlance of our times, can the
theory be "clockworked"? We argue that a clockwork construction producing a
potential for an axion of fundamental period
will obey the constraint . For some applications, including
chromonatural inflation with sub-Planckian field range, this constraint
obstructs a clockwork UV completion. Alternative routes to a large coupling
include fields of large charge (an approach limited by strong coupling) or
kinetic mixing (requiring a lighter axion). Our results suggest that
completions of axion cosmologies that explain the large parameter in the theory
potentially alter the phenomenological predictions of the model
Flavored dark matter beyond Minimal Flavor Violation
We study the interplay of flavor and dark matter phenomenology for models of
flavored dark matter interacting with quarks. We allow an arbitrary flavor
structure in the coupling of dark matter with quarks. This coupling is assumed
to be the only new source of violation of the Standard Model flavor symmetry
extended by a associated with the dark matter. We call this ansatz
Dark Minimal Flavor Violation (DMFV) and highlight its various implications,
including an unbroken discrete symmetry that can stabilize the dark matter. As
an illustration we study a Dirac fermionic dark matter which transforms
as triplet under , and is a singlet under the Standard Model. The
dark matter couples to right-handed down-type quarks via a colored scalar
mediator with a coupling . We identify a number of
"flavor-safe" scenarios for the structure of which are beyond Minimal
Flavor Violation. For dark matter and collider phenomenology we focus on the
well-motivated case of -flavored dark matter. The combined flavor and dark
matter constraints on the parameter space of turn out to be
interesting intersections of the individual ones. LHC constraints on simplified
models of squarks and sbottoms can be adapted to our case, and monojet searches
can be relevant if the spectrum is compressed.Comment: 40 pages, 19 figures, 3 tables. Clarifying comments and some
references added, matches published versio
A Couplet from Flavored Dark Matter
We show that a couplet, a pair of closely spaced photon lines, in the X-ray
spectrum is a distinctive feature of lepton flavored dark matter models for
which the mass spectrum is dictated by Minimal Flavor Violation. In such a
scenario, mass splittings between different dark matter flavors are determined
by Standard Model Yukawa couplings and can naturally be small, allowing all
three flavors to be long-lived and contribute to the observed abundance. Then,
in the presence of a tiny source of flavor violation, heavier dark matter
flavors can decay via a dipole transition on cosmological timescales, giving
rise to three photon lines. The ratios of the line energies are completely
determined in terms of the charged lepton masses, and constitute a firm
prediction of this framework. For dark matter masses of order the weak scale,
the couplet lies in the keV-MeV region, with a much weaker line in the eV-keV
region. This scenario constitutes a potential explanation for the recent claim
of the observation of a 3.5 keV line. The next generation of X-ray telescopes
may have the necessary resolution to resolve the double line structure of such
a couplet.Comment: 17 pages, 4 figures, 1 haik
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