135 research outputs found
Local heating of the universe by the Higgs field
© 2018 World Scientific Publishing Company It is shown that the creation of primordial massive black holes is accompanied by a local heating of the matter. The developed mechanism is based on the interaction of the Higgs field and a scalar field responsible for black hole formation. We also consider dynamical behavior of parameters such as a scale and chemical composition of such heating regions
Constraints on dark matter-nucleon effective couplings in the presence of kinematically distinct halo substructures using the DEAP-3600 detector
DEAP-3600 is a single-phase liquid argon detector aiming to directly detect
Weakly Interacting Massive Particles (WIMPs), located at SNOLAB (Sudbury,
Canada). After analyzing data taken during the first year of operation, a null
result was used to place an upper bound on the WIMP-nucleon spin-independent,
isoscalar cross section. This study reinterprets this result within a
Non-Relativistic Effective Field Theory framework, and further examines how
various possible substructures in the local dark matter halo may affect these
constraints. Such substructures are hinted at by kinematic structures in the
local stellar distribution observed by the Gaia satellite and other recent
astronomical surveys. These include the Gaia Sausage (or Enceladus), as well as
a number of distinct streams identified in recent studies. Limits are presented
for the coupling strength of the effective contact interaction operators
, , , , and
, considering isoscalar, isovector, and xenonphobic
scenarios, as well as the specific operators corresponding to millicharge,
magnetic dipole, electric dipole, and anapole interactions. The effects of halo
substructures on each of these operators are explored as well, showing that the
and operators are particularly sensitive to the
velocity distribution, even at dark matter masses above 100 GeV/
The liquid-argon scintillation pulseshape in DEAP-3600
DEAP-3600 is a liquid-argon scintillation detector looking for dark matter. Scintillation events in the liquid argon (LAr) are registered by 255 photomultiplier tubes (PMTs), and pulseshape discrimination (PSD) is used to suppress electromagnetic background events. The excellent PSD performance of LAr makes it a viable target for dark matter searches, and the LAr scintillation pulseshape discussed here is the basis of PSD. The observed pulseshape is a combination of LAr scintillation physics with detector effects. We present a model for the pulseshape of electromagnetic background events in the energy region of interest for dark matter searches. The model is composed of (a) LAr scintillation physics, including the so-called intermediate component, (b) the time response of the TPB wavelength shifter, including delayed TPB emission at
O(ms) time-scales, and c) PMT response. TPB is the wavelength shifter of choice in most LAr detectors. We find that approximately 10% of the intensity of the wavelength-shifted light is in a long-lived state of TPB. This causes light from an event to spill into subsequent events to an extent not usually accounted for in the design and data analysis of LAr-based detectors
Search for dark matter-nucleon interactions via Migdal effect with DarkSide-50
Dark matter elastic scattering off nuclei can result in the excitation and
ionization of the recoiling atom through the so-called Migdal effect. The
energy deposition from the ionization electron adds to the energy deposited by
the recoiling nuclear system and allows for the detection of interactions of
sub-GeV/c mass dark matter. We present new constraints for sub-GeV/c
dark matter using the dual-phase liquid argon time projection chamber of the
DarkSide-50 experiment with an exposure of (12306 184) kg d. The analysis
is based on the ionization signal alone and significantly enhances the
sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses
down to 40 MeV/c. Furthermore, it sets the most stringent upper limit on
the spin independent dark matter nucleon cross section for masses below
GeV/c.Comment: 7 pages, 3 figure
Search for dark matter annual modulation with DarkSide-50
Dark matter induced event rate in an Earth-based detector is predicted to
show an annual modulation as a result of the Earth's orbital motion around the
Sun. We searched for this modulation signature using the ionization signal of
the DarkSide-50 liquid argon time projection chamber. No significant signature
compatible with dark matter is observed in the electron recoil equivalent
energy range above , the lowest threshold ever achieved in
such a search.Comment: 8 pages, 4 figure
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