27 research outputs found
PeV scale Supersymmetry breaking and the IceCube neutrino flux
The observation of very high energy neutrino events at IceCube has grasped a
lot of attention in the fields of both astrophysics and particle physics. It
has been speculated that these high energy neutrinos might originate either
from purely conventional astrophysical sources or from the late decay of a
super heavy (PeV scale) dark matter (DM) particle. In order for decaying DM to
be a dominant source of the IceCube high-energy neutrinos, it would require an
unusually suppressed value of the coupling of DM to neutrinos. We attempt to
explain this small coupling in the context of an -parity conserving minimal
supergravity model which has right-handed neutrino superfields. With the main
assumptions of super-partner masses at the PeV scale and also a reheating
temperature not much larger than the PeV scale, we find in our model several
natural order-of-magnitude "miracles", (i) the gravitino is produced via
freeze-in as a DM candidate with the correct relic density (ii) the
right-handed (RH) sneutrino makes up only a tiny fraction (, of the
present day energy density of the universe, yet its decay lifetime to the
gravitino and neutrinos is such that it naturally predicts the right
order-of-magnitude for the IceCube neutrino flux. The long lifetime of the RH
sneutrino is explained by the existence of a global -symmetry which is only
broken due to supersymmetry breaking effects. Our model also predicts a flux of
100 TeV gamma rays from the decaying RH sneutrino which are within the current
observational constraints.Comment: v2: 34 pages, 6 figures, Journal version (published in JHEP
WIMPless Dark Matter from an AMSB Hidden Sector with No New Mass Parameters
We present a model with dark matter in an anomaly-mediated supersymmetry
breaking hidden sector with a U(1)xU(1) gauge symmetry. The symmetries of the
model stabilize the dark matter and forbid the introduction of new mass
parameters. As a result, the thermal relic density is completely determined by
the gravitino mass and dimensionless couplings. Assuming non-hierarchical
couplings, the thermal relic density is ~ 0.1, independent of the dark matter's
mass and interaction strength, realizing the WIMPless miracle. The model has
several striking features. For particle physics, stability of the dark matter
is completely consistent with R-parity violation in the visible sector, with
implications for superpartner collider signatures; also the thermal relic's
mass may be ~ 10 GeV or lighter, which is of interest given recent direct
detection results. Interesting astrophysical signatures are dark matter
self-interactions through a long-range force, and massless hidden photons and
fermions that contribute to the number of relativistic degrees of freedom at
BBN and CMB. The latter are particularly interesting, given current indications
for extra degrees of freedom and near future results from the Planck
observatory.Comment: 18 pages, pdflate
WIMPless Dark Matter in Anomaly-Mediated Supersymmetry Breaking with Hidden QED
In anomaly-mediated supersymmetry breaking, superpartners in a hidden sector
have masses that are proportional to couplings squared, and so naturally freeze
out with the desired dark matter relic density for a large range of masses. We
present an extremely simple realization of this possibility, with WIMPless dark
matter arising from a hidden sector that is supersymmetric QED with N_F
flavors. Dark matter is multi-component, composed of hidden leptons and
sleptons with masses anywhere from 10 GeV to 10 TeV, and hidden photons provide
the thermal bath. The dark matter self-interacts through hidden sector Coulomb
scatterings that are potentially observable. In addition, the hidden photon
contribution to the number of relativistic degrees of freedom is in the range
\Delta N_eff ~ 0 - 2, and, if the hidden and visible sectors were initially in
thermal contact, the model predicts \Delta N_eff ~ 0.2 - 0.4. Data already
taken by Planck may provide evidence of such deviations.Comment: 17 page
Astrometric Microlensing of Primordial Black Holes with Gaia
The Gaia space telescope allows for unprecedented accuracy for astrometric
measurements of stars in the Galaxy. In this work, we explore the sensitivity
of Gaia to detect primordial black hole (PBH) dark matter through the
distortions that PBHs would create in the apparent trajectories of background
stars, an effect known as astrometric microlensing (AML). We present a novel
calculation of the lensing probability, and we combine this with the publicly
released Gaia eDR3 stellar catalog to predict the expected rate of AML events
that Gaia will see. We also compute the expected distribution of a few event
observables, which will be useful for reducing backgrounds. We argue that the
astrophysical background rate of AML like events due to other sources is
negligible (except possibly for very long duration events), and we use this to
compute the potential exclusion that could be set on the parameter space of
PBHs with a monochromatic mass function. We find that Gaia is sensitive to PBHs
in the range of - , and has peak sensitivity
to PBHs of for which it can rule out as little as a fraction
of dark matter composed of PBHs. With this exquisite
sensitivity, Gaia has the potential to rule out a PBH origin for the
gravitational wave signals seen at LIGO/Virgo. Our novel calculation of the
lensing probability includes for the first time, the effect of intermediate
duration lensing events, where the lensing event lasts for a few years, but for
a period which is still shorter than the Gaia mission lifetime. The lower end
of our predicted mass exclusion is especially sensitive to this class of
lensing events. As and when time-series data for Gaia is released, our
prediction of the lensing rate and event observable distributions will be
useful to estimate the true exclusion/discovery of the PBH parameter space
utilizing this data.Comment: 45 pages, 11 figures, 2 tables. Updates in response to referee
comments; main results unchange
Tagging Boosted Ws with Wavelets
We present a new technique for distinguishing the hadronic decays of boosted
heavy particles from QCD backgrounds based on wavelet transforms. As an initial
exploration, we illustrate the technique in the particular case of hadronic
boson decays, comparing it to the ``mass drop'' cut currently used by the LHC
experiments. We apply wavelet cuts, which make use of complementary
information, and in combination with the mass drop cut results in an
improvement of 7% in discovery reach of hadronic boson final states
over a wide range of transverse momenta.Comment: 14 pages, 5 figure