77 research outputs found
Origin of the tentative AMS antihelium events
We demonstrate that the tentative detection of a few antihelium events with
the Alpha Magnetic Spectrometer (AMS) on board the International Space Station
can, in principle, be ascribed to the annihilation or decay of Galactic dark
matter, when accounting for uncertainties in the coalescence process leading to
the formation of antinuclei. We show that the predicted antiproton rate,
assuming the antihelium events came from dark matter, is marginally consistent
with AMS data, as is the antideuteron rate with current available constraints.
We argue that a dark matter origin can be tested with better constraints on the
coalescence process, better control of misidentified events, and with future
antideuteron data.Comment: 6 pages, 2 figures. Updated to match version accepted by Phys. Rev.
Monochromatic Gamma Rays from Dark Matter Annihilation to Leptons
We investigate the relation between the annihilation of dark matter (DM)
particles into lepton pairs and into 2-body final states including one or two
photons. We parametrize the DM interactions with leptons in terms of contact
interactions, and calculate the loop-level annihilation into monochromatic
gamma rays, specifically computing the ratio of the DM annihilation cross
sections into two gamma rays versus lepton pairs. While the loop-level
processes are generically suppressed in comparison with the tree-level
annihilation into leptons, we find that some choices for the mediator spin and
coupling structure lead to large branching fractions into gamma-ray lines. This
result has implications for a dark matter contribution to the AMS-02 positron
excess. We also explore the possibility of mediators which are charged under a
dark symmetry and find that, for these loop-level processes, an effective field
theory description is accurate for DM masses up to about half the mediator
mass.Comment: 21 pages plus appendices, 7 figures. v2: added experimental
constraints from CMB and Fermi, expanded and reorganized discussion
throughout. Accepted by JHE
Primordial Black Holes as Silver Bullets for New Physics at the Weak Scale
Observational constraints on gamma rays produced by the annihilation of
weakly interacting massive particles around primordial black holes (PBHs) imply
that these two classes of Dark Matter candidates cannot coexist. We show here
that the successful detection of one or more PBHs by radio searches (with the
Square Kilometer Array) and gravitational waves searches (with LIGO/Virgo and
the upcoming Einstein Telescope) would set extraordinarily stringent
constraints on virtually all weak-scale extensions of the Standard Model with
stable relics, including those predicting a WIMP abundance much smaller than
that of Dark Matter. Upcoming PBHs searches have in particular the potential to
rule out almost the entire parameter space of popular theories such as the
minimal supersymmetric standard model and scalar singlet Dark Matter.Comment: 10 pages, 3 figures. Code available at
https://github.com/adam-coogan/pbhs_vs_wimps , archived at
https://zenodo.org/badge/latestdoi/169754838 . v2: Matches version published
in PR
Hazma: A Python Toolkit for Studying Indirect Detection of Sub-GeV Dark Matter
With several proposed MeV gamma-ray telescopes on the horizon, it is of
paramount importance to perform accurate calculations of gamma-ray spectra
expected from sub-GeV dark matter annihilation and decay. We present hazma, a
python package for reliably computing these spectra, determining the resulting
constraints from existing gamma-ray data, and prospects for upcoming
telescopes. For high-level analyses, hazma comes with several built-in dark
matter models where the interactions between dark matter and hadrons have been
determined in detail using chiral perturbation theory. Additionally, hazma
provides tools for computing spectra from individual final states with
arbitrary numbers of light leptons and mesons, and for analyzing custom dark
matter models. hazma can also produce electron and positron spectra from dark
matter annihilation, enabling precise derivation of constraints from the cosmic
microwave background.Comment: Minor revisions; fixed typos in FSR spectr
Connecting direct and indirect detection with a dark spike in the cosmic-ray electron spectrum
Multiple space-borne cosmic ray detectors have detected line-like features in
the electron and positron spectra. Most recently, the DAMPE collaboration
reported the existence of such a feature at 1.4 TeV, sparking interest in a
potential dark matter origin. Such quasi-monochromatic features, virtually free
of any astrophysical background, could be explained by the annihilation of dark
matter particles in a nearby dark matter clump. Here, we explore the
consistency of producing such spectral features with dark matter annihilation
from the standpoint of dark matter substructure statistics, constraints from
anisotropy, and constraints from gamma-ray emission. We demonstrate that if
indeed a high-energy, line-like feature in the electron-positron spectrum
originates from dark matter annihilation in a nearby clump, a significant or
even dominant fraction of the dark matter in the Solar System likely stems from
the clump, with dramatic consequences for direct dark matter searches.Comment: 30 pages, 11 figure
Connecting direct and indirect detection with a dark spike in the cosmic-ray electron spectrum
Multiple space-borne cosmic ray detectors have detected line-like features in
the electron and positron spectra. Most recently, the DAMPE collaboration
reported the existence of such a feature at 1.4 TeV, sparking interest in a
potential dark matter origin. Such quasi-monochromatic features, virtually free
of any astrophysical background, could be explained by the annihilation of dark
matter particles in a nearby dark matter clump. Here, we explore the
consistency of producing such spectral features with dark matter annihilation
from the standpoint of dark matter substructure statistics, constraints from
anisotropy, and constraints from gamma-ray emission. We demonstrate that if
indeed a high-energy, line-like feature in the electron-positron spectrum
originates from dark matter annihilation in a nearby clump, a significant or
even dominant fraction of the dark matter in the Solar System likely stems from
the clump, with dramatic consequences for direct dark matter searches.Comment: 30 pages, 11 figure
Sampling-Based Accuracy Testing of Posterior Estimators for General Inference
Parameter inference, i.e. inferring the posterior distribution of the
parameters of a statistical model given some data, is a central problem to many
scientific disciplines. Generative models can be used as an alternative to
Markov Chain Monte Carlo methods for conducting posterior inference, both in
likelihood-based and simulation-based problems. However, assessing the accuracy
of posteriors encoded in generative models is not straightforward. In this
paper, we introduce `Tests of Accuracy with Random Points' (TARP) coverage
testing as a method to estimate coverage probabilities of generative posterior
estimators. Our method differs from previously-existing coverage-based methods,
which require posterior evaluations. We prove that our approach is necessary
and sufficient to show that a posterior estimator is accurate. We demonstrate
the method on a variety of synthetic examples, and show that TARP can be used
to test the results of posterior inference analyses in high-dimensional spaces.
We also show that our method can detect inaccurate inferences in cases where
existing methods fail.Comment: 15 pages, Accepted at ICML 202
Strong-Lensing Source Reconstruction with Denoising Diffusion Restoration Models
Analysis of galaxy--galaxy strong lensing systems is strongly dependent on
any prior assumptions made about the appearance of the source. Here we present
a method of imposing a data-driven prior / regularisation for source galaxies
based on denoising diffusion probabilistic models (DDPMs). We use a pre-trained
model for galaxy images, AstroDDPM, and a chain of conditional reconstruction
steps called denoising diffusion reconstruction model (DDRM) to obtain samples
consistent both with the noisy observation and with the distribution of
training data for AstroDDPM. We show that these samples have the qualitative
properties associated with the posterior for the source model: in a
low-to-medium noise scenario they closely resemble the observation, while
reconstructions from uncertain data show greater variability, consistent with
the distribution encoded in the generative model used as prior.Comment: Accepted for the NeurIPS 2022 workshop Machine Learning and the
Physical Sciences; 9 pages, 4 figure
Measuring dark matter spikes around primordial black holes with Einstein Telescope and Cosmic Explorer
Future ground-based gravitational wave observatories will be ideal probes of
the environments surrounding black holes with masses . Binary black hole mergers with mass ratios of order
can remain in the frequency band of such detectors
for months or years, enabling precision searches for modifications of their
gravitational waveforms with respect to vacuum inspirals. As a concrete example
of an environmental effect, we consider here a population of binary primordial
black holes which are expected to be embedded in dense cold dark matter spikes.
We provide a viable formation scenario for these systems compatible with all
observational constraints, and predict upper and lower limits on the merger
rates of small mass ratio pairs. Given a detected signal of one such system by
either Einstein Telescope or Cosmic Explorer, we show that the properties of
the binary and of the dark matter spike can be measured to excellent precision
with one week's worth of data, if the effect of the dark matter spike on the
waveform is taken into account. However, we show that there is a risk of biased
parameter inference or missing the events entirely if the effect of the
predicted dark matter overdensity around these objects is not properly
accounted for.Comment: 14 pages plus appendices, 15 figure
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