3 research outputs found
Cosmic ray electrons and positrons from discrete stochastic sources
The distances that galactic cosmic ray electrons and positrons can travel are
severely limited by energy losses to at most a few kiloparsec, thereby
rendering the local spectrum very sensitive to the exact distribution of
sources in our galactic neighbourhood. However, due to our ignorance of the
exact source distribution, we can only predict the spectrum stochastically. We
argue that even in the case of a large number of sources the central limit
theorem is not applicable, but that the standard deviation for the flux from a
random source is divergent due to a long power law tail of the probability
density. Instead, we compute the expectation value and characterise the scatter
around it by quantiles of the probability density using a generalised central
limit theorem in a fully analytical way. The uncertainty band is asymmetric
about the expectation value and can become quite large for TeV energies. In
particular, the predicted local spectrum is marginally consistent with the
measurements by Fermi-LAT and HESS even without imposing spectral breaks or
cut-offs at source. We conclude that this uncertainty has to be properly
accounted for when predicting electron fluxes above a few hundred GeV from
astrophysical sources.Comment: 16 pages, 8 figures; references and clarifying comment added; to
appear in JCA
Complementarity of Galactic radio and collider data in constraining WIMP dark matter models
In this work we confront dark matter models to constraints that may be
derived from radio synchrotron radiation from the Galaxy, taking into account
the astrophysical uncertainties and we compare these to bounds set by
accelerator and complementary indirect dark matter searches. Specifically we
apply our analysis to three popular particle physics models. First, a generic
effective operator approach, in which case we set bounds on the corresponding
mass scale, and then, two specific UV completions, the Z' and Higgs portals. We
show that for many candidates, the radio synchrotron limits are competitive
with the other searches, and could even give the strongest constraints (as of
today) with some reasonable assumptions regarding the astrophysical
uncertainties.Comment: 22 pages, 12 figure
Interpretation of AMS-02 Results: Correlations among Dark Matter Signals
The AMS-02 collaboration has recently released data on the positron fraction
up to energies of about 350 GeV. If one insists on interpreting
the observed excess as a dark matter signal, then we find it is best described
by a TeV-scale dark matter annihilating into , although this
situation is already severely constrained by gamma-ray measurements. The
annihilation into is allowed by gamma-rays more than
, but it gives a poorer fit to \textsc{AMS-02} data. Moreover,
since electroweak corrections induce correlations among the fluxes of stable
particles from dark matter annihilations, the recent AMS-02 data imply a
well-defined prediction for the correlated flux of antiprotons. Under the
assumption that their future measurements will not show any antiproton excess
above the background, the dark matter interpretation of the positron rise will
possibly be ruled out by only making use of data from a single experiment. This
work is the first of a program where we emphasize the role of correlations
among dark matter signals.Comment: 12 pages, 4 figures. Published versio