665 research outputs found
A Fresh Approach to Forecasting in Astroparticle Physics and Dark Matter Searches
We present a toolbox of new techniques and concepts for the efficient
forecasting of experimental sensitivities. These are applicable to a large
range of scenarios in (astro-)particle physics, and based on the Fisher
information formalism. Fisher information provides an answer to the question
what is the maximum extractable information from a given observation?. It is a
common tool for the forecasting of experimental sensitivities in many branches
of science, but rarely used in astroparticle physics or searches for particle
dark matter. After briefly reviewing the Fisher information matrix of general
Poisson likelihoods, we propose very compact expressions for estimating
expected exclusion and discovery limits (equivalent counts method). We
demonstrate by comparison with Monte Carlo results that they remain
surprisingly accurate even deep in the Poisson regime. We show how correlated
background systematics can be efficiently accounted for by a treatment based on
Gaussian random fields. Finally, we introduce the novel concept of Fisher
information flux. It can be thought of as a generalization of the commonly used
signal-to-noise ratio, while accounting for the non-local properties and
saturation effects of background and instrumental uncertainties. It is a
powerful and flexible tool ready to be used as core concept for informed
strategy development in astroparticle physics and searches for particle dark
matter.Comment: 33 pages, 12 figure
Is the 130 GeV Line Real? A Search for Systematics in the Fermi-LAT Data
Our recent claims of a Galactic center feature in Fermi-LAT data at
approximately 130 GeV have prompted an avalanche of papers proposing
explanations ranging from dark matter annihilation to exotic pulsar winds.
Because of the importance of such interpretations for physics and astrophysics,
a discovery will require not only additional data, but a thorough investigation
of possible LAT systematics. While we do not have access to the details of each
event reconstruction, we do have information about each event from the public
event lists and spacecraft parameter files. These data allow us to search for
suspicious trends that could indicate a spurious signal. We consider several
hypotheses that might make an instrumental artifact more apparent at the
Galactic center, and find them implausible. We also search for an instrumental
signature in the Earth limb photons, which provide a smooth reference spectrum
for null tests. We find no significant 130 GeV feature in the Earth limb
sample. However, we do find a marginally significant 130 GeV feature in Earth
limb photons with a limited range of detector incidence angles. This raises
concerns about the 130 GeV Galactic center feature, even though we can think of
no plausible model of instrumental behavior that connects the two. A modest
amount of additional limb data would tell us if the limb feature is a
statistical fluke. If the limb feature persists, it would raise doubts about
the Pass 7 processing of E > 100 GeV events. At present we find no instrumental
systematics that could plausibly explain the excess Galactic center emission at
130 GeV.Comment: 16 pages, 22 figure
Bayesian Model Comparison and Analysis of the Galactic Disk Population of Gamma-Ray Millisecond Pulsars
Pulsed emission from almost one hundred millisecond pulsars (MSPs) has been
detected in -rays by the Fermi Large-Area Telescope. The global
properties of this population remain relatively unconstrained despite many
attempts to model their spatial and luminosity distributions. We perform here a
self-consistent Bayesian analysis of both the spatial distribution and
luminosity function simultaneously. Distance uncertainties, arising from errors
in the parallax measurement or Galactic electron-density model, are
marginalized over. We provide a public Python package for calculating distance
uncertainties to pulsars derived using the dispersion measure by accounting for
the uncertainties in Galactic electron-density model YMW16. Finally, we use
multiple parameterizations for the MSP population and perform Bayesian model
comparison, finding that a broken power law luminosity function with Lorimer
spatial profile are preferred over multiple other parameterizations used in the
past. The best-fit spatial distribution and number of -ray MSPs is
consistent with results for the radio population of MSPs.Comment: 13 pages, 8 figures, 3 tables + Appendix. Public code and source list
available from http://github.com/tedwards2412/MSPDis
A Unique Multi-Messenger Signal of QCD Axion Dark Matter
We propose a multi-messenger probe of QCD axion Dark Matter based on
observations of black hole-neutron star binary inspirals. It is suggested that
a dense Dark Matter spike may grow around intermediate mass black holes
(). The presence of such a spike produces
two unique effects: a distinct phase shift in the gravitational wave strain
during the inspiral and an enhancement of the radio emission due to the
resonant axion-photon conversion occurring in the neutron star magnetosphere
throughout the inspiral and merger. Remarkably, the observation of the
gravitational wave signal can be used to infer the Dark Matter density and,
consequently, to predict the radio emission. We study the projected reach of
the LISA interferometer and next-generation radio telescopes such as the Square
Kilometre Array. Given a sufficiently nearby system, such observations will
potentially allow for the detection of QCD axion Dark Matter in the mass range
to .Comment: 5 pages, 3 figures. Appendix added with additional figures. Updated
to published versio
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