85 research outputs found
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
Search for dark matter particle interactions with electron final states with DarkSide-50
We present a search for dark matter particles with sub-GeV/ masses whose
interactions have final state electrons using the DarkSide-50 experiment's
(12306 184) kg d low-radioactivity liquid argon exposure. By analyzing
the ionization signals, we exclude new parameter space for the dark
matter-electron cross section , the axioelectric coupling
constant , and the dark photon kinetic mixing parameter . We
also set the first dark matter direct-detection constraints on the mixing angle
for keV sterile neutrinos.Comment: 6 pages, 2 figure
Study of cosmogenic activation above ground for the DarkSide-20k experiment
The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating
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background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods
DarkSide status and prospects
Sem informaçãoDarkSide uses a dual-phase Liquid Argon Time Projection Chamber to search for WIMP dark matter. The current detector, DarkSide-50, is running since mid 2015 with a target of 50 kg of Argon from an underground source. Here it is presented the latest results of searches of WIMP-nucleus interactions, with WIMP masses in the GeV-TeV range, and of WIMP-electron interactions, in the sub-GeV mass range. The future of DarkSide with a new generation experiment, involving a global collaboration from all the current Argon based experiments, is presented.422-315Sem informaçãoSem informaçãoSem informaçã
Directionality of nuclear recoils in a liquid argon time projection chamber
The direct search for dark matter in the form of weakly interacting massive
particles (WIMP) is performed by detecting nuclear recoils (NR) produced in a
target material from the WIMP elastic scattering. A promising experimental
strategy for direct dark matter search employs argon dual-phase time projection
chambers (TPC). One of the advantages of the TPC is the capability to detect
both the scintillation and charge signals produced by NRs. Furthermore, the
existence of a drift electric field in the TPC breaks the rotational symmetry:
the angle between the drift field and the momentum of the recoiling nucleus can
potentially affect the charge recombination probability in liquid argon and
then the relative balance between the two signal channels. This fact could make
the detector sensitive to the directionality of the WIMP-induced signal,
enabling unmistakable annual and daily modulation signatures for future
searches aiming for discovery. The Recoil Directionality (ReD) experiment was
designed to probe for such directional sensitivity. The TPC of ReD was
irradiated with neutrons at the INFN Laboratori Nazionali del Sud, and data
were taken with 72 keV NRs of known recoil directions. The direction-dependent
liquid argon charge recombination model by Cataudella et al. was adopted and a
likelihood statistical analysis was performed, which gave no indications of
significant dependence of the detector response to the recoil direction. The
aspect ratio R of the initial ionization cloud is estimated to be 1.037 +/-
0.027 and the upper limit is R < 1.072 with 90% confidence levelComment: 20 pages, 10 figures, submitted to Eur. Phys. J.
Study on cosmogenic activation above ground for the DarkSide-20k project
The activation of materials due to the exposure to cosmic rays may become an
important background source for experiments investigating rare event phenomena.
DarkSide-20k is a direct detection experiment for galactic dark matter
particles, using a two-phase liquid argon time projection chamber filled with
49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Here,
the cosmogenic activity of relevant long-lived radioisotopes induced in the
argon and other massive components of the set-up has been estimated; production
of 120 t of radiopure UAr is foreseen. The expected exposure above ground and
production rates, either measured or calculated, have been considered. From the
simulated counting rates in the detector due to cosmogenic isotopes, it is
concluded that activation in copper and stainless steel is not problematic.
Activation of titanium, considered in early designs but not used in the final
design, is discussed. The activity of 39Ar induced during extraction,
purification and transport on surface, in baseline conditions, is evaluated to
be 2.8% of the activity measured in UAr from the same source, and thus
considered acceptable. Other products in the UAr such as 37Ar and 3H are shown
to not be relevant due to short half-life and assumed purification methods
Sensitivity projections for a dual-phase argon TPC optimized for light dark matter searches through the ionization channel
Dark matter lighter than 10 GeV/c2 encompasses a promising range of candidates. A conceptual design for a new detector, DarkSide-LowMass, is presented, based on the DarkSide-50 detector and progress toward DarkSide-20k, optimized for a low-threshold electron-counting measurement. Sensitivity to light dark matter is explored for various potential energy thresholds and background rates. These studies show that DarkSide-LowMass can achieve sensitivity to light dark matter down to the solar neutrino fog for GeV-scale masses and significant sensitivity down to 10 MeV/c2 considering the Migdal effect or interactions with electrons. Requirements for optimizing the detector’s sensitivity are explored, as are potential sensitivity gains from modeling and mitigating spurious electron backgrounds that may dominate the signal at the lowest energies
Sensitivity projections for a dual-phase argon TPC optimized for light dark matter searches through the ionization channel
Dark matter lighter than 10 GeV/c encompasses a promising range of
candidates. A conceptual design for a new detector, DarkSide-LowMass, is
presented, based on the DarkSide-50 detector and progress toward DarkSide-20k,
optimized for a low-threshold electron-counting measurement. Sensitivity to
light dark matter is explored for various potential energy thresholds and
background rates. These studies show that DarkSide-LowMass can achieve
sensitivity to light dark matter down to the solar neutrino floor for GeV-scale
masses and significant sensitivity down to 10 MeV/c considering the Migdal
effect or interactions with electrons. Requirements for optimizing the
detector's sensitivity are explored, as are potential sensitivity gains from
modeling and mitigating spurious electron backgrounds that may dominate the
signal at the lowest energies
SiPM-matrix readout of two-phase argon detectors using electroluminescence in the visible and near infrared range
Proportional electroluminescence (EL) in noble gases is used in two-phase detectors for dark matter searches to record (in the gas phase) the ionization signal induced by particle scattering in the liquid phase. The “standard” EL mechanism is considered to be due to noble gas excimer emission in the vacuum ultraviolet (VUV). In addition, there are two alternative mechanisms, producing light in the visible and near infrared (NIR) ranges. The first is due to bremsstrahlung of electrons scattered on neutral atoms (“neutral bremsstrahlung”, NBrS). The second, responsible for electron avalanche scintillation in the NIR at higher electric fields, is due to transitions between excited atomic states. In this work, we have for the first time demonstrated two alternative techniques of the optical readout of two-phase argon detectors, in the visible and NIR range, using a silicon photomultiplier matrix and electroluminescence due to either neutral bremsstrahlung or avalanche scintillation. The amplitude yield and position resolution were measured for these readout techniques, which allowed to assess the detection threshold for electron and nuclear recoils in two-phase argon detectors for dark matter searches. To the best of our knowledge, this is the first practical application of the NBrS effect in detection science
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