DAMIC: a novel dark matter experiment

Proceedings of The 39th International Conference on High Energy Physics — PoS(ICHEP2018), 2019

Advances in High Energy Physics, 2015

Although the existence of dark matter is supported by many evidences, based on astrophysical measurements, its nature is still completely unknown. One major candidate is represented by weakly interacting massive particles (WIMPs), which could in principle be detected through their collisions with ordinary nuclei in a sensitive target, producing observable low-energy (<100 keV) nuclear recoils. The DarkSide program aims at the WIPMs detection using a liquid argon time projection chamber (LAr-TPC). In this paper we quickly review the DarkSide program focusing in particular on the next generation experiment DarkSide-G2, a 3.6-ton LAr-TPC. The different detector components are described as well as the improvements needed to scale the detector from DarkSide-50 (50 kg LAr-TPC) up to DarkSide-G2. Finally, the preliminary results on background suppression and expected sensitivity are presented.

Physics of the Dark Universe, 2012

Dark matter with mass below about a GeV is essentially unobservable in conventional direct detection experiments. However, newly proposed technology will allow the detection of single electron events in semiconductor materials with significantly lowered thresholds. This would allow detection of dark matter as light as an MeV in mass. Compared to other detection technologies, semiconductors allow enhanced sensitivity because of their low ionization energy around an eV. Such detectors would be particularly sensitive to dark matter with electric and magnetic dipole moments, with a reach many orders of magnitude beyond current bounds. Observable dipole moment interactions can be generated by new particles with masses as great as ∼ 10 3 TeV, providing a window to scales beyond the reach of current colliders.

Physical Review D, 2013

The next generation of large scale WIMP direct detection experiments have the potential to go beyond the discovery phase and reveal detailed information about both the particle physics and astrophysics of dark matter. We report here on early results arising from the development of a detailed numerical code modeling the proposed DARWIN detector, involving both liquid argon and xenon targets. We incorporate realistic detector physics, particle physics and astrophysical uncertainties and demonstrate to what extent two targets with similar sensitivities can remove various degeneracies and allow a determination of dark matter cross sections and masses while also probing rough aspects of the dark matter phase space distribution. We find that, even assuming dominance of spin-independent scattering, multi-ton scale experiments still have degeneracies that depend sensitively on the dark matter mass, and on the possibility of isospin violation and inelasticity in interactions. We find that these experiments are best able to discriminate dark matter properties for dark matter masses less than around 200 GeV. In addition, and somewhat surprisingly, the use of two targets gives only a small improvement (aside from the advantage of different systematics associated with any claimed signal) in the ability to pin down dark matter parameters when compared with one target of larger exposure.

Physical Review D, 2014

We present a search for low-mass (≤ 20 GeV/c 2 ) weakly interacting massive particles (WIMPs), strong candidates of dark matter particles, using the low-background CsI(Tl) detector array of the Korea Invisible Mass Search (KIMS) experiment. With a total data exposure of 24,324.3 kg·days, we search for WIMP interaction signals produced by nuclei recoiling from WIMP-nuclear elastic scattering with visible energies between 2 and 4 keV. The observed energy distribution of candidate events is consistent with null signals, and upper limits of the WIMP-proton spin-independent interaction are set with a 90% confidence level. The observed limit rejects most of the low mass region of parameter space favored by the DAMA annual modulation signal.

Journal of High Energy Physics, 2016

Dark matter in the sub-GeV mass range is a theoretically motivated but largely unexplored paradigm. Such light masses are out of reach for conventional nuclear recoil direct detection experiments, but may be detected through the small ionization signals caused by dark matter-electron scattering. Semiconductors are well-studied and are particularly promising target materials because their O(1 eV) band gaps allow for ionization signals from dark matter particles as light as a few hundred keV. Current direct detection technologies are being adapted for dark matter-electron scattering. In this paper, we provide the theoretical calculations for dark matter-electron scattering rate in semiconductors, overcoming several complications that stem from the many-body nature of the problem. We use density functional theory to numerically calculate the rates for dark matter-electron scattering in silicon and germanium, and estimate the sensitivity for upcoming experiments such as DAMIC and SuperCDMS. We find that the reach for these upcoming experiments has the potential to be orders of magnitude beyond current direct detection constraints and that sub-GeV dark matter has a sizable modulation signal. We also give the first direct detection limits on sub-GeV dark matter from its scattering off electrons in a semiconductor target (silicon) based on published results from DAMIC. We make available publicly our code, QEdark, with which we calculate our results. Our results can be used by experimental collaborations to calculate their own sensitivities based on their specific setup. The searches we propose will probe vast new regions of unexplored dark matter model and parameter space.

Physical Review Letters, 2020

We present the first direct-detection search for sub-GeV dark matter using a new ∼2-gram highresistivity Skipper-CCD from a dedicated fabrication batch that was optimized for dark-matter searches. Using 24 days of data acquired in the MINOS cavern at the Fermi National Accelerator Laboratory, we measure the lowest rates in silicon detectors of events containing one, two, three, or four electrons, and achieve world-leading sensitivity for a large range of sub-GeV dark matter masses. Data taken with different thicknesses of the detector shield suggest a correlation between the rate of high-energy tracks and the rate of single-electron events previously classified as "dark current." We detail key characteristics of the new Skipper-CCDs, which augur well for the planned construction of the ∼100-gram SENSEI experiment at SNOLAB.

arXiv (Cornell University), 2013

1. Significant progress in theoretical studies has been made to assess the detectability of Dark Matter (DM) particle models by various experiments. These studies have been conducted both in the framework of UV-complete theories, for example supersymmetry (SUSY), and in the context of effective theories, such as with higher-dimensional contact operators. Both methods can be employed to relate accelerator constraints to the detectability of signatures from weakly interacting massive particles (WIMPs). SUSY scans including the latest constraints from the LHC, and cosmological constraints show that the Cherenkov Telescope Array (CTA) can greatly improve the current experimental sensitivity over the parameter space of many theoretical DM models. 2. CTA, with a critical enhancement provided by the U.S., would provide a powerful new tool for searching for dark matter, covering parameter space not accessible to other techniques (direct searches, accelerator). CTA would provide new information that will help identify the particle nature of the DM (mass, spectral signatures of the specific annihilation channel) and could provide a measurement of the halo profile. Given the importance of indirect detection (ID) to Dark matter science, DOE and NSF/Physics contribution to indirect detection experiment, on the level of its commitment to the G2 Direct Detection experiments, could result in a U.S. dark matter program with a realistic prospect for both detecting the dark matter in the lab and identifying it on the sky. 3. After the LHC has covered the a priori natural parameter space for SUSY, it is a priority in this field to further explore the viable theory parameter space of both supersymmetric models and other extensions to the Standard Model. Indirect detection experiments (gamma-ray and neutrino measurements in particular) can, in some cases, go beyond the limits of the Energy Frontier of terrestrial accelerators. 4. The field of indirect dark matter detection necessitates a coherent theoretical and observational effort to pinpoint via astrophysical modeling and measurements the relevant inputs to detection rates, such as the density, velocity distribution and substructure content of dark matter halos. Multi-wavelength and cosmic-ray searches are also in need of additional observational and theoretical efforts, especially in the realm of Galactic propagation and energy losses for charged species. We recommend, on both fronts, arXiv:1310.7040v1 [astro-ph.HE] 25 Oct 2013 2 a broad community based effort to improve measurements (e.g., identifying new Dwarf galaxies and improving the stellar velocity data on important objects; performing key multi-wavelength and cosmicray measurements to characterize the magnetic field structure in the Galaxy and determine secondaryto-primary ratios of light cosmic-ray nuclei) and conduct more realistic simulation studies (with higher resolution N-body simulations, and more detailed modeling of baryonic feedback). Progress in this field will allow us to both quantify uncertainties, and to converge on benchmark models for astrophysical inputs and for cosmic-ray diffusion models, which will allow for a direct comparison of performance and expected sensitivity for current and future experiments. 5. The Galactic center is a prime target for DM searches. Even without rejection of astrophysical backgrounds, observations of the GC provide strong constraints. For CTA, i.e. the next generation experiment, angular resolution is key to improving ability to reject astrophysical backgrounds in the GC. To achieve good angular resolution, and good sensitivity to southern sources doubling the size of the proposed southern CTA telescope is key. Merging telescopes in a single site, and improving angular resolution is much more than an incremental improvement. 6. IceCube with the DeepCore/PINGU/MICA enhancement (in-filling the instrument to achieve a significantly lower energy threshold) would provide the possibility of detecting a smoking-gun signal of DM (a high-energy neutrino signal from the Sun) as well as competitive limits on the spin-dependent SD nuclear recoil cross section compared with planned generation-2 (G2) direct detection experiments. 7. Continued operation of Fermi, HAWC, and VERITAS over the next ∼5 years will result in dramatic improvements in sensitivity to dark matter covering the energy range from GeV up to the unitarity limit of ∼100 TeV. These observations are projected to provide between a factor of 2 and order-ofmagnitude improvements compared to existing limits over this range. Collectively, these experiments would provide the best sensitivity to the northern-hemisphere ("classical") dwarf galaxies, even after the first (southern) CTA array comes on line.

Journal of Low Temperature Physics, 2008

The Cryogenic Dark Matter Search (CDMS) experiment is searching for Weakly Interacting Massive Particles (WIMPs) using detectors with the ability to discriminate between candidate (nuclear recoil) and background (electron recoil) events by measuring both phonon and ionization signals from recoils in the detector crystals. As CDMS scales up to greater WIMP sensitivity, it is necessary to increase the detector mass and further improve background discrimination. CDMS is engaged in ongoing fabrication and development of new detector designs in order to meet these criteria for the proposed SuperCDMS experiment. Thicker detector prototypes have been produced with new photolithographic masks. These masks have greater surface coverage of the quasi particle trap and transition edge sensor system to provide J Low Temp Phys (2008) 151: 211-215 superior athermal phonon collection. Results from continuing laboratory tests are presented which already indicate improvement in discrimination parameters. Keywords SuperCDMS · Dark matter PACS 95.35.+d · 14.80.Ly · 29.40.Vj · 85.25.Oj · 73.61.Jc · 85.25.-j · 74.78.-w · 85.25.Oj