11,204 research outputs found
CP Violating Baryon Oscillations
We enumerate the conditions necessary for violation to be manifest in
- oscillations, and build a simple model that can give rise to such
effects. We discuss a possible connection between neutron oscillations and dark
matter, provided the mass of the latter lies between and .
We apply our results to a possible baryogenesis scenario involving
violation in the oscillations of the .Comment: 8 pages, 2 figures. v2: version to appear in PR
Inflationary Axion Cosmology Beyond Our Horizon
In theories of axion dark matter with large axion decay constant, temperature
variations in the CMB are extremely sensitive to perturbations in the initial
axion field, allowing one to place a lower bound on the total amount of
inflation. The most stringent bound comes from axion strings, which for axion
decay constant f=10^17 GeV would currently be observable at a distance of 6 x
10^16 light-years, nearly ten million times as far away as our horizon
Baryogenesis via Mesino Oscillations
We propose a new mechanism for baryogenesis at the 1-200 MeV scale.
Enhancement of CP violation takes place via interference between oscillations
and decays of mesinos--bound states of a scalar quark and antiquark and their
CP conjugates. We present the mechanism in a simplified model with four new
fundamental particles, with masses between 300 GeV and 10 TeV, and show that
some of the experimentally allowed parameter space can give the observed
baryon-to-entropy ratio.Comment: 14 pages, 6 figure
CP Violation in Pseudo-Dirac Fermion Oscillations
Supersymmetric theories with a symmetry have Dirac gauginos, solve
the supersymmetric flavor and CP problems, and have distinctive collider
signatures. However when supergravity is included, the must be broken,
adding small Majorana mass terms which split the mass of the two components of
the Dirac gaugino and lead to oscillations between charge eigenstates.
We present a general study of fermion-antifermion oscillations in this system,
including the effects of decays and CP violation. We consider the effects of
such oscillations in the case where the two charge eigenstates can
decay into the same final state, and show that CP violation is allowed.
In the case of decays into final states containing leptons such CP violation
can be observed as a same sign dilepton asymmetry.Comment: 12 pages, 4 figures, v2: references added, typos correcte
A Renormalizable Model for the Galactic Center Gamma Ray Excess from Dark Matter Annihilation
Evidence for an excess of gamma rays with O(GeV) energy coming from the
center of our galaxy has been steadily accumulating over the past several
years. Recent studies of the excess in data from the Fermi telescope have cast
doubt on an explanation for the excess arising from unknown astrophysical
sources. A potential source of the excess is the annihilation of dark matter
into standard model final states, giving rise to gamma ray production. The
spectrum of the excess is well fit by 30 GeV dark matter annihilating into a
pair of b quarks with a cross section of the same order of magnitude as
expected for a thermal relic. Simple models that can lead to this annihilation
channel for dark matter are in strong tension with null results from direct
detection experiments. We construct a renormalizable model where dark
matter-standard model interactions are mediated by a pseudoscalar that mixes
with the CP-odd component of a pair of Higgs doublets, allowing for the gamma
ray excess to be explained while suppressing the direct detection signal. We
consider implications for this scenario from Higgs decays, rare B meson decays
and monojet searches and also comment on some difficulties that any dark matter
model explaining the gamma ray excess via direct annihilation into quarks will
encounter.Comment: 9 pages, 2 figures. v2: published version, references added, B_s->mu
mu limits and estimates update
Little flavor: A model of weak-scale flavor physics
We describe a model of quarks which identifies the large global symmetries of
little Higgs models with the global flavor symmetries that arise in a
deconstruction of the extra-dimensional 'topological insulator' model of
flavor. The nonlinearly realized symmetries of little Higgs theories play a
critical role in determining the flavor structure of fermion masses and mixing.
All flavor physics occurs at the few TeV scale in this model, yet flavor
changing neutral currents arising from the new physics are naturally smaller
than those generated radiatively in the standard model, without having to
invoke minimal flavor violation.Comment: 17 pages, 3 figures. Minor revisions to align with version accepted
for publication, including title, and additional discussion about
phenomenolog
Is CP a Gauge Symmetry?
We suggest here that CP is a discrete {\it gauge} symmetry, and is therefore
not violated by quantum gravity. We show that four dimensional CP can arise as
a discrete gauge symmetry in theories with dimensional compactification, if the
original number of Minkowski dimensions equals , or , and if
there are certain restrictions on the gauge group; these conditions are met by
superstrings. CP may then be broken spontaneously below GeV, explaining
the observed CP violation in the kaon system without inducing a large EDMN. We
discuss the phenomenology of such models, as well as the peculiar nature of
cosmic ``CP strings'' which could be produced at the compactification scale.
Such strings have the curious property that a particle carried around the
string is turned into its CP conjugate. A single CP string renders four
dimensional spacetime nonorientable.Comment: 2
Counting 4 pi 's in Strongly Coupled Supersymmetry
We extend the "naive dimensional analysis" arguments used in QCD for
estimating the strengths of operators in chiral Lagrangians to strongly coupled
supersymmetric theories. In particular, we show how to count factors of 4 pi
---an inexact science, but nevertheless a useful art when such theories are
used to model real particle physics.Comment: 11 pages, late
Testing m(up)=0 on the Lattice
A massless up quark is an intriguing solution to the strong CP problem. We
discuss how lattice computations can be used in conjunction with chiral
perturbation theory to address the consistency of with the observed
hadron spectrum and interactions. It is not necessary to simulate very light
quarks-three flavor partially quenched computations with comparable sea and
valence quark masses on the order of the strange quark mass could suffice.Comment: 20 pages, corrected equations, added ref
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