We present a summary of future prospects for direct detection of dark matter within the GeV/c2 to TeV/c2 mass range. This is paired with a new definition of the neutrino fog in order to better quantify the rate of diminishing returns on sensitivity due to irreducible neutrino backgrounds. A survey of dark matter candidates predicted to fall within this mass range demonstrates that fully testing multiple well-motivated theo-ries will require expanding the currently-funded generation of experiments down to and past the neutrino fog. We end with the status and plans for next-generation exper-iments and novel R&D concepts which will get us there.

We are conducting an experiment to search for WIMPs, or weakly-interacting massive particles, in the galactic halo using terrestrial detectors. This generic class of hypothetical particles, whose properties are similar to those predicted by extensions of the standard model of particle physics, could comprise the cold component of non-baryonic dark matter. We describe our experiment, which is based on cooled germanium and silicon detectors in a shielded low-background cryostat. The detectors achieve a high degree of background rejection through the simultaneous measurement of the energy in phonons and ionization. Using exposures on the order of one kilogram-day from initial runs of our experiment, we have achieved (preliminary) upper limits on the WIMP-nucleon cross section that are comparable to much longer runs of other experiments.

The dual-phase xenon time projection chamber (TPC) is a powerful tool for direct-detection experiments searching for WIMP dark matter, other dark matter models, and neutrinoless double-beta decay. Successful operation of such a TPC is critically dependent on the ability to hold high electric fields in the bulk liquid, across the liquid surface, and in the gas. Careful design and construction of the electrodes used to establish these fields is therefore required. We present the design and production of the LUX-ZEPLIN (LZ) experiment's high-voltage electrodes, a set of four woven mesh wire grids. Grid design drivers are discussed, with emphasis placed on design of the electron extraction region. We follow this with a description of the grid production process and a discussion of steps taken to validate the LZ grids prior to integration into the TPC.

Data taken during the final shallow-site run of the first tower of the Cryogenic Dark Matter Search (CDMS II) detectors have been reanalyzed with improved sensitivity to small energy depositions. Four ∼224g germanium and two ∼105g silicon detectors were operated at the Stanford Underground Facility (SUF) between December 2001 and June 2002, yielding 118 live days of raw exposure. Three of the germanium and both silicon detectors were analyzed with a new low-threshold technique, making it possible to lower the germanium and silicon analysis thresholds down to the actual trigger thresholds of ∼1 and ∼2keV, respectively. Limits on the spin-independent cross section for weakly interacting massive particles (WIMPs) to elastically scatter from nuclei based on these data exclude interesting parameter space for WIMPs with masses below 9GeV/c2. Under standard halo assumptions, these data partially exclude parameter space favored by interpretations of the DAMA/LIBRA and CoGeNT experiments' data as WIMP signals, and exclude new parameter space for WIMP masses between 3 and 4GeV/c2. © 2010 The American Physical Society.

The Large Underground Xenon (LUX) dark matter search experiment is currently being deployed at the Homestake Laboratory in South Dakota. We will highlight the main elements of design which make the experiment a very strong competitor in the field of direct detection, as well as an easily scalable concept. We will also present its potential reach for supersymmetric dark matter detection, within various timeframes ranging from 1 year to 5 years or more. © 2010 American Institute of Physics.

The dual-phase xenon time projection chamber (TPC) is a powerful tool for direct-detection experiments searching for WIMP dark matter, other dark matter models, and neutrinoless double-beta decay. Successful operation of such a TPC is critically dependent on the ability to hold high electric fields in the bulk liquid, across the liquid surface, and in the gas. Careful design and construction of the electrodes used to establish these fields is therefore required. We present the design and production of the LUX-ZEPLIN (LZ) experiment's high-voltage electrodes, a set of four woven mesh wire grids. Grid design drivers are discussed, with emphasis placed on design of the electron extraction region. We follow this with a description of the grid production process and a discussion of steps taken to validate the LZ grids prior to integration into the TPC.

Results are presented from radioactivity screening of two models of photomultiplier tubes designed for use in current and future liquid xenon experiments. The Hamamatsu 5.6 cm diameter R8778 PMT, used in the LUX dark matter experiment, has yielded a positive detection of four common radioactive isotopes: 238U, 232Th, 40K, and 60Co. Screening of LUX materials has rendered backgrounds from other detector materials subdominant to the R8778 contribution. A prototype Hamamatsu 7.6 cm diameter R11410 MOD PMT has also been screened, with benchmark isotope counts measured at <0.4 238U/<0.3 232Th/<8.3 40K/2.0±0.2 60Co mBq/PMT. This represents a large reduction, equal to a change of ×124 238U/×19 232Th/×18 40K per PMT, between R8778 and R11410 MOD, concurrent with a doubling of the photocathode surface area (4.5-6.4 cm diameter). 60Co measurements are comparable between the PMTs, but can be significantly reduced in future R11410 MOD units through further material selection. Assuming PMT activity equal to the measured 90% upper limits, Monte Carlo estimates indicate that replacement of R8778 PMTs with R11410 MOD PMTs will change LUX PMT electron recoil background contributions by a factor of ×125 after further material selection for 60Co reduction, and nuclear recoil backgrounds by a factor of ×136. The strong reduction in backgrounds below the measured R8778 levels makes the R11410 MOD a very competitive technology for use in large-scale liquid xenon detectors. © 2012 Elsevier B.V. All rights reserved.

© Proceedings of the 2011 Meeting of the Division of Particles and Fields of the American Physical Society, DPF 2011. All rights reserved. The LZ program consists of two stages of direct dark matter searches using liquid Xe detectors. The first stage will be a 1.5-3 tonne detector, while the last stage will be a 20 tonne detector. Both devices will benefit tremendously from research and development performed for the LUX experiment, a 350 kg liquid Xe dark matter detector currently operating at the Sanford Underground Laboratory. In particular, the technology used for cryogenics and electrical feedthroughs, circulation and purification, low-background materials and shielding techniques, electronics, calibrations, and automated control and recovery systems are all directly scalable from LUX to the LZ detectors. Extensive searches for potential background sources have been performed, with an emphasis on previously undiscovered background sources that may have a significant impact on tonne-scale detectors. The LZ detectors will probe spin-independent interaction cross sections as low as 5 × 10-49 cm2 for 100 GeV WIMPs, which represents the ultimate limit for dark matter detection with liquid xenon technology.

The LUX detector is currently in operation at the Davis Campus at the 4850' level of the Sanford Underground Research Facility (SURF) in Lead, SD to directly search for WIMP dark matter. Knowing the type and rate of backgrounds is critical in a rare, low energy event search, and LUX was designed, constructed, and deployed to mitigate backgrounds, both internal and external. An important internal background are decays of radon and its daughters. These consist of alpha decays, which are easily tagged and are a tracer of certain backgrounds, and beta decays, some of which are not as readily tagged and present a background for the WIMP search. We report on studies of alpha decay and discuss implications for the WIMP search.

The Large Underground Xenon (LUX) dark matter experiment aims to detect rare low-energy interactions from Weakly Interacting Massive Particles (WIMPs). The radiogenic backgrounds in the LUX detector have been measured and compared with Monte Carlo simulation. Measurements of LUX high-energy data have provided direct constraints on all background sources contributing to the background model. The expected background rate from the background model for the 85.3 day WIMP search run is (2.6±0.2stat±0.4sys) ×10-3 events keVee-1kg-1day-1 in a 118 kg fiducial volume. The observed background rate is (3.6±0.4 stat)×10-3 events keVee-1kg-1day- 1, consistent with model projections. The expectation for the radiogenic background in a subsequent one-year run is presented. © 2014 Elsevier B.V. All rights reserved.