32 research outputs found
Sfermion Interference in Neutralino Decays at the LHC
If the two lightest neutralinos of the Minimal Supersymmetric Standard Model
have a mass splitting less than the Z boson mass, interference effects in the
three-body decay chi_2^0 --> chi_1^0 f f can be important. We formulate an
observable that contains information on the nature of the interference: the
ratio BR(chi_2^0 --> chi_1^0 b b) / BR(chi_2^0 --> chi_1^0 l+ l-). This will
give a constraint on the supersymmetry breaking parameters that is
complementary to many techniques already existing in the literature. We present
some ideas on how to perform a simple counting experiment to determine this
ratio.Comment: 14 pages, 6 figure
On the Correlation Between the Spin-Independent and Spin-Dependent Direct Detection of Dark Matter
We study the correlation between spin-independent and spin-dependent
scattering in the context of MSSM neutralino dark matter for both thermal and
non-thermal histories. We explore the generality of this relationship with
reference to other models. We discuss why either fine-tuning or numerical
coincidences are necessary for the correlation to break down. We derive upper
bounds on spin-dependent scattering mediated by a Z boson.Comment: 31 pages, 6 figures, 3 appendices; v2: refs added, minor typos
corrected, journal versio
Model-Independent Description and Large Hadron Collider Implications of Suppressed Two-Photon Decay of a Light Higgs Boson
For a Standard Model Higgs boson with mass between 115 GeV and 150 GeV, the
two-photon decay mode is important for discovery at the Large Hadron Collider
(LHC). We describe the interactions of a light Higgs boson in a more
model-independent fashion, and consider the parameter space where there is no
two-photon decay mode. We argue from generalities that analysis of the discovery mode outside its normally thought of range of applicability is
especially needed under these circumstances. We demonstrate the general
conclusion with a specific example of parameters of a type I two-Higgs doublet
theory, motivated by ideas in strongly coupled model building. We then specify
a complete set of branching fractions and discuss the implications for the LHC.Comment: 4 pages, 4 figure
Asymmetric Dark Matter from a GeV Hidden Sector
Asymmetric Dark Matter (ADM) models relate the dark matter density to the
baryon asymmetry, so that a natural mass scale for ADM is around a few GeV. In
existing models of ADM, this mass scale is unexplained; here we generate this
GeV scale for dark matter (DM) from the weak scale via gauge kinetic mixing
with a new Abelian dark force. In addition, this dark sector provides an
efficient mechanism for suppressing the symmetric abundance of DM through
annihilations to the dark photon. We augment this sector with a higher
dimensional operator responsible for communicating the baryon asymmetry to the
dark sector. Our framework also provides DM candidate for gauge mediation
models. It results in a direct detection cross section of interest for current
experiments: sigma less than or similar to 10^{-42} cm^2 for DM masses in the
range 1 - 15 GeV.Comment: 21 pages, 4 figure
Pulsars as a source of the WMAP haze
The WMAP haze is an excess in the 22 to 93 GHz frequency bands of WMAP extending about 10 degrees from the galactic center. We show that synchrotron emission from electron-positron pairs injected into the interstellar medium by the galactic population of pulsars with energies in the 1 to 100 GeV range can explain the frequency spectrum of the WMAP haze and the drop in the average haze power with latitude. The same spectrum of high energy electron-positron pairs from pulsars, which gives rise to the haze, may also generate the observed excesses in AMS, HEAT and PAMELA. We discuss the spatial morphology of the pulsar synchrotron signal and its deviation from spherical symmetry, which may provide an avenue to determine the pulsar contribution to the haze
Supersymmetric Baryogenesis from Exotic Quark Decays
In a simple extension of the minimal supersymmetric standard model,
out-of-equilibrium decays of TeV scale exotic vector-like squarks may generate
the baryon asymmetry of the universe. Baryon number and CP violation are
present in the superpotential, so this mechanism does not rely on CP violation
in supersymmetry breaking parameters. We discuss phenomenological constraints
on the model as well as potential signals for the Large Hadron Collider and
electronic dipole moment experiments. A variation on the TeV scale model allows
the exotic squarks to be the messengers of gauge mediated supersymmetry
breaking.Comment: 28 pages, 7 figures, 2 appendices, v2: typos corrected, results
unchange
Is the PAMELA Positron Excess Winos?
Recently the PAMELA satellite-based experiment reported an excess of galactic
positrons that could be a signal of annihilating dark matter. The PAMELA data
may admit an interpretation as a signal from a wino-like LSP of mass about 200
GeV, normalized to the local relic density, and annihilating mainly into
W-bosons. This possibility requires the current conventional estimate for the
energy loss rate of positrons be too large by roughly a factor of five. Data
from anti-protons and gamma rays also provide tension with this interpretation,
but there are significant astrophysical uncertainties associated with their
propagation. It is not unreasonable to take this well-motivated candidate
seriously, at present, in part because it can be tested in several ways soon.
The forthcoming PAMELA data on higher energy positrons and the FGST (formerly
GLAST) data, should provide important clues as to whether this scenario is
correct. If correct, the wino interpretation implies a cosmological history in
which the dark matter does not originate in thermal equilibrium.Comment: 7 pages, 4 figue
Neutralino Dark Matter from Indirect Detection Revisited
We revisit indirect detection possibilities for neutralino dark matter,
emphasizing the complementary roles of different approaches. While thermally
produced dark matter often requires large astrophysical "boost factors" to
observe antimatter signals, the physically motivated alternative of non-thermal
dark matter can naturally provide interesting signals, for example from light
wino or Higgsino dark matter. After a brief review of cosmic ray propagation,
we discuss signals for positrons, antiprotons, synchrotron radiation and gamma
rays from wino annihilation in the galactic halo, and examine their
phenomenology. For pure wino dark matter relevant to the LHC, PAMELA and GLAST
should report signals.Comment: 23 pages, 9 figures: v2. Corrected typos, fixed synchrotron bounds in
light of bugs in progra
Pulsars as a source of the WMAP haze
The WMAP haze is an excess in the 22 to 93 GHz frequency bands of WMAP extending about 10 degrees from the galactic center. We show that synchrotron emission from electron-positron pairs injected into the interstellar medium by the galactic population of pulsars with energies in the 1 to 100 GeV range can explain the frequency spectrum of the WMAP haze and the drop in the average haze power with latitude. The same spectrum of high energy electron-positron pairs from pulsars, which gives rise to the haze, may also generate the observed excesses in AMS, HEAT and PAMELA. We discuss the spatial morphology of the pulsar synchrotron signal and its deviation from spherical symmetry, which may provide an avenue to determine the pulsar contribution to the haze