22 research outputs found
Nuclear Recoil Identification in a Scientific Charge-Coupled Device
Charge-coupled devices (CCDs) are a leading technology in direct dark matter
searches because of their eV-scale energy threshold and high spatial
resolution. The sensitivity of future CCD experiments could be enhanced by
distinguishing nuclear recoil signals from electronic recoil backgrounds in the
CCD silicon target. We present a technique for event-by-event identification of
nuclear recoils based on the spatial correlation between the primary ionization
event and the lattice defect left behind by the recoiling atom, later
identified as a localized excess of leakage current under thermal stimulation.
By irradiating a CCD with an AmBe neutron source, we demonstrate
identification efficiency for nuclear recoils with energies keV,
where the ionization events were confirmed to be nuclear recoils from topology.
The technique remains fully efficient down to 90 keV, decreasing to 50 at 8
keV, and reaching () at 1.5--3.5 keV. Irradiation with a Na
-ray source shows no evidence of defect generation by electronic
recoils, with the fraction of electronic recoils with energies keV that
are spatially correlated with defects .Comment: 9 pages, 7 figure
Search for Daily Modulation of MeV Dark Matter Signals with DAMIC-M
Dark Matter (DM) particles with sufficiently large cross sections may scatter
as they travel through Earth's bulk. The corresponding changes in the DM flux
give rise to a characteristic daily modulation signal in detectors sensitive to
DM-electron interactions. Here, we report results obtained from the first
underground operation of the DAMIC-M prototype detector searching for such a
signal from DM with MeV-scale mass. A model-independent analysis finds no
modulation in the rate of 1 events with periods in the range 1-48 h. We
then use these data to place exclusion limits on DM in the mass range [0.53,
2.7] MeV/c interacting with electrons via a dark photon mediator. Taking
advantage of the time-dependent signal we improve by 2 orders of
magnitude on our previous limit obtained from the total rate of 1 events,
using the same data set. This daily modulation search represents the current
strongest limit on DM-electron scattering via ultralight mediators for DM
masses around 1 MeV/c
Skipper-CCD Sensors for the Oscura Experiment: Requirements and Preliminary Tests
Oscura is a proposed multi-kg skipper-CCD experiment designed for a dark
matter (DM) direct detection search that will reach unprecedented sensitivity
to sub-GeV DM-electron interactions with its 10 kg detector array. Oscura is
planning to operate at SNOLAB with 2070 m overburden, and aims to reach a
background goal of less than one event in each electron bin in the 2-10
electron ionization-signal region for the full 30 kg-year exposure, with a
radiation background rate of 0.01 dru. In order to achieve this goal, Oscura
must address each potential source of background events, including instrumental
backgrounds. In this work, we discuss the main instrumental background sources
and the strategy to control them, establishing a set of constraints on the
sensors' performance parameters. We present results from the tests of the first
fabricated Oscura prototype sensors, evaluate their performance in the context
of the established constraints and estimate the Oscura instrumental background
based on these results
Early Science with the Oscura Integration Test
Oscura is a planned light-dark matter search experiment using Skipper-CCDs
with a total active mass of 10 kg. As part of the detector development, the
collaboration plans to build the Oscura Integration Test (OIT), an engineering
test experiment with 10% of the Oscura's total mass. Here we discuss the early
science opportunities with the OIT to search for millicharged particles (mCPs)
using the NuMI beam at Fermilab. mCPs would be produced at low energies through
photon-mediated processes from decays of scalar, pseudoscalar, and vector
mesons, or direct Drell-Yan productions. Estimates show that the OIT would be a
world-leading probe for low-mass mCPs.Comment: 21 pages, 13 figure
Nuclear Recoil Identification in a Scientific Charge-Coupled Device
International audienceCharge-coupled devices (CCDs) are a leading technology in direct dark matter searches because of their eV-scale energy threshold and high spatial resolution. The sensitivity of future CCD experiments could be enhanced by distinguishing nuclear recoil signals from electronic recoil backgrounds in the CCD silicon target. We present a technique for event-by-event identification of nuclear recoils based on the spatial correlation between the primary ionization event and the lattice defect left behind by the recoiling atom, later identified as a localized excess of leakage current under thermal stimulation. By irradiating a CCD with an AmBe neutron source, we demonstrate identification efficiency for nuclear recoils with energies keV, where the ionization events were confirmed to be nuclear recoils from topology. The technique remains fully efficient down to 90 keV, decreasing to 50 at 8 keV, and reaching () at 1.5--3.5 keV. Irradiation with a Na -ray source shows no evidence of defect generation by electronic recoils, with the fraction of electronic recoils with energies keV that are spatially correlated with defects
Search for Daily Modulation of MeV Dark Matter Signals with DAMIC-M
International audienceDark Matter (DM) particles with sufficiently large cross sections may scatter as they travel through Earth's bulk. The corresponding changes in the DM flux give rise to a characteristic daily modulation signal in detectors sensitive to DM-electron interactions. Here, we report results obtained from the first underground operation of the DAMIC-M prototype detector searching for such a signal from DM with MeV-scale mass. A model-independent analysis finds no modulation in the rate of 1 events with periods in the range 1-48 h. We then use these data to place exclusion limits on DM in the mass range [0.53, 2.7] MeV/c interacting with electrons via a dark photon mediator. Taking advantage of the time-dependent signal we improve by 2 orders of magnitude on our previous limit obtained from the total rate of 1 events, using the same data set. This daily modulation search represents the current strongest limit on DM-electron scattering via ultralight mediators for DM masses around 1 MeV/c
Search for Daily Modulation of MeV Dark Matter Signals with DAMIC-M
International audienceDark Matter (DM) particles with sufficiently large cross sections may scatter as they travel through Earth's bulk. The corresponding changes in the DM flux give rise to a characteristic daily modulation signal in detectors sensitive to DM-electron interactions. Here, we report results obtained from the first underground operation of the DAMIC-M prototype detector searching for such a signal from DM with MeV-scale mass. A model-independent analysis finds no modulation in the rate of 1 events with periods in the range 1-48 h. We then use these data to place exclusion limits on DM in the mass range [0.53, 2.7] MeV/c interacting with electrons via a dark photon mediator. Taking advantage of the time-dependent signal we improve by 2 orders of magnitude on our previous limit obtained from the total rate of 1 events, using the same data set. This daily modulation search represents the current strongest limit on DM-electron scattering via ultralight mediators for DM masses around 1 MeV/c
Search for Daily Modulation of MeV Dark Matter Signals with DAMIC-M
International audienceDark Matter (DM) particles with sufficiently large cross sections may scatter as they travel through Earth's bulk. The corresponding changes in the DM flux give rise to a characteristic daily modulation signal in detectors sensitive to DM-electron interactions. Here, we report results obtained from the first underground operation of the DAMIC-M prototype detector searching for such a signal from DM with MeV-scale mass. A model-independent analysis finds no modulation in the rate of 1 events with periods in the range 1-48 h. We then use these data to place exclusion limits on DM in the mass range [0.53, 2.7] MeV/c interacting with electrons via a dark photon mediator. Taking advantage of the time-dependent signal we improve by 2 orders of magnitude on our previous limit obtained from the total rate of 1 events, using the same data set. This daily modulation search represents the current strongest limit on DM-electron scattering via ultralight mediators for DM masses around 1 MeV/c
First Constraints from DAMIC-M on Sub-GeV Dark-Matter Particles Interacting with Electrons
International audienceWe report constraints on sub-GeV dark matter particles interacting with electrons from the first underground operation of DAMIC-M detectors. The search is performed with an integrated exposure of 85.23 g days, and exploits the sub-electron charge resolution and low level of dark current of DAMIC-M Charge-Coupled Devices (CCDs). Dark-matter-induced ionization signals above the detector dark current are searched for in CCD pixels with charge up to 7 e-. With this data set we place limits on dark matter particles of mass between 0.53 and 1000 MeV/c2, excluding unexplored regions of parameter space in the mass ranges [1.6,1000] MeV/c2 and [1.5,15.1] MeV/c2 for ultra-light and heavy mediator interactions, respectively
First Constraints from DAMIC-M on Sub-GeV Dark-Matter Particles Interacting with Electrons
International audienceWe report constraints on sub-GeV dark matter particles interacting with electrons from the first underground operation of DAMIC-M detectors. The search is performed with an integrated exposure of 85.23 g days, and exploits the sub-electron charge resolution and low level of dark current of DAMIC-M Charge-Coupled Devices (CCDs). Dark-matter-induced ionization signals above the detector dark current are searched for in CCD pixels with charge up to 7 e-. With this data set we place limits on dark matter particles of mass between 0.53 and 1000 MeV/c2, excluding unexplored regions of parameter space in the mass ranges [1.6,1000] MeV/c2 and [1.5,15.1] MeV/c2 for ultra-light and heavy mediator interactions, respectively