88 research outputs found
Probing Exotic Physics With Supernova Neutrinos
Future galactic supernovae will provide an extremely long baseline for
studying the properties and interactions of neutrinos. In this paper, we
discuss the possibility of using such an event to constrain (or discover) the
effects of exotic physics in scenarios that are not currently constrained and
are not accessible with reactor or solar neutrino experiments. In particular,
we focus on the cases of neutrino decay and quantum decoherence. We calculate
the expected signal from a core-collapse supernova in both current and future
water Cerenkov, scintillating, and liquid argon detectors, and find that such
observations will be capable of distinguishing between many of these scenarios.
Additionally, future detectors will be capable of making strong,
model-independent conclusions by examining events associated with a galactic
supernova's neutronization burst.Comment: 19 pages, 6 figure
Directly detecting Isospin-Violating Dark Matter
We consider the prospects for multiple dark matter direct detection
experiments to determine if the interactions of a dark matter candidate are
isospin-violating. We focus on theoretically well-motivated examples of
isospin-violating dark matter (IVDM), including models in which dark matter
interactions with nuclei are mediated by a dark photon, a Z, or a squark. We
determine that the best prospects for distinguishing IVDM from the
isospin-invariant scenario arise in the cases of dark photon- or Z-mediated
interactions, and that the ideal experimental scenario would consist of large
exposure xenon- and neon-based detectors. If such models just evade current
direct detection limits, then one could distinguish such models from the
standard isospin-invariant case with two detectors with of order 100 ton-year
exposure.Comment: 16 pages, 4 figures, 2 tables. Published versio
Examining the time dependence of DAMA's modulation amplitude
If dark matter is composed of weakly interacting particles, Earth's orbital
motion may induce a small annual variation in the rate at which these particles
interact in a terrestrial detector. The DAMA collaboration has identified at a
9.3 confidence level such an annual modulation in their event rate over
two detector iterations, DAMA/NaI and DAMA/LIBRA, each with years of
observations. We statistically examine the time dependence of the modulation
amplitudes, which "by eye" appear to be decreasing with time in certain energy
ranges. We perform a chi-squared goodness of fit test of the average modulation
amplitudes measured\ by the two detector iterations which rejects the
hypothesis of a consistent modulation amplitude at greater than 80\%, 96\%, and
99.6\% for the 2--4~keVee, 2--5~keVee and 2--6~keVee energy ranges,
respectively. We also find that among the 14 annual cycles there are three
departures from the average in the 5-6~keVee energy range. In
addition, we examined several phenomenological models for the time dependence
of the modulation amplitude. Using a maximum likelihood test, we find that
descriptions of the modulation amplitude as decreasing with time are preferred
over a constant modulation amplitude at anywhere between 1 and
3, depending on the phenomenological model for the time dependence and
the signal energy range considered. A time dependent modulation amplitude is
not expected for a dark matter signal, at least for dark matter halo
morphologies consistent with the DAMA signal. New data from DAMA/LIBRA--phase2
will certainly aid in determining whether any apparent time dependence is a
real effect or a statistical fluctuation.Comment: 13 pages, 1 figur
A Study of Dark Matter and QCD-Charged Mediators in the Quasi-Degenerate Regime
We study a scenario in which the only light new particles are a Majorana
fermion dark matter candidate and one or more QCD-charged scalars, which couple
to light quarks. This scenario has several interesting phenomenological
features if the new particles are nearly degenerate in mass. In particular, LHC
searches for the light scalars have reduced sensitivity, since the visible and
invisible products tend to be softer. Moreover, dark matter-scalar
co-annihilation can allow even relatively heavy dark matter candidates to be
consistent thermal relics. Finally, the dark matter nucleon scattering cross
section is enhanced in the quasi-degenerate limit, allowing direct detection
experiments to use both spin-independent and spin-dependent scattering to probe
regions of parameter space beyond those probed by the LHC. Although this
scenario has broad application, we phrase this study in terms of the MSSM, in
the limit where the only light sparticles are a bino-like dark matter candidate
and light-flavored squarks.Comment: 24 pages, 5 figures; as published in PRD with significant revision
The Muon Anomalous Magnetic Moment in the Reduced Minimal 3-3-1 Model
We study the muon anomalous magnetic moment in the context of
the reduced minimal 3-3-1 model recently proposed in the literature. In
particular, its spectrum contains a doubly charged scalar () and
gauge boson (), new singly charged vectors () and a
boson, each of which might give a sizeable contribution to the
. We compute the 1-loop contributions from all these new particles
to the . We conclude that the doubly charged vector boson provides
the dominant contribution, and by comparing our results with the experimental
constraints we derive an expected value for the scale of symmetry breaking TeV. We also note that, if the
discrepancy in the anomalous moment is resolved in the future without this
model then the constraints will tighten to requiring TeV with
current precision, and will entirely rule out the model if the expected
precision is achieved by the future experiment at Fermilab.Comment: 19 pages, 4 figure
The impact of baryons on the direct detection of dark matter
The spatial and velocity distributions of dark matter particles in the Milky
Way Halo affect the signals expected to be observed in searches for dark
matter. Results from direct detection experiments are often analyzed assuming a
simple isothermal distribution of dark matter, the Standard Halo Model (SHM).
Yet there has been skepticism regarding the validity of this simple model due
to the complicated gravitational collapse and merger history of actual
galaxies. In this paper we compare the SHM to the results of cosmological
hydrodynamical simulations of galaxy formation to investigate whether or not
the SHM is a good representation of the true WIMP distribution in the analysis
of direct detection data. We examine two Milky Way-like galaxies from the
MaGICC cosmological simulations (a) with dark matter only and (b) with baryonic
physics included. The inclusion of baryons drives the shape of the DM halo to
become more spherical and makes the velocity distribution of dark matter
particles less anisotropic especially at large heliocentric velocities, thereby
making the SHM a better fit. We also note that we do not find a significant
disk-like rotating dark matter component in either of the two galaxy halos with
baryons that we examine, suggesting that dark disks are not a generic
prediction of cosmological hydrodynamical simulations. We conclude that in the
Solar neighborhood, the SHM is in fact a good approximation to the true dark
matter distribution in these cosmological simulations (with baryons) which are
reasonable representations of the Milky Way, and hence can also be used for the
purpose of dark matter direct detection calculations.Comment: Minor changes to match JCAP version. 21 pages, 9 figure
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