D. J. Taylor

First results from the LUX dark matter experiment at the Sanford Underground Research Facility

The Large Underground Xenon (LUX) experiment is a dual-phase xenon time-projection chamber operating at the Sanford Underground Research Facility (Lead, South Dakota). The LUX cryostat was filled for the first time in the underground laboratory in February 2013. We report results of the first WIMP search data set, taken during the period from April to August 2013, presenting the analysis of 85.3 live days of data with a fiducial volume of 118 kg. A profile-likelihood analysis technique shows our data to be consistent with the background-only hypothesis, allowing 90% confidence limits to be set on spin-independent WIMP-nucleon elastic scattering with a minimum upper limit on the cross section of 7.6 × 10(-46) cm(2) at a WIMP mass of 33 GeV/c(2). We find that the LUX data are in disagreement with low-mass WIMP signal interpretations of the results from several recent direct detection experiments.

The Large Underground Xenon (LUX) Experiment

The Large Underground Xenon (LUX) collaboration has designed and constructed a dual-phase xenon detector, in order to conduct a search for Weakly Interacting Massive Particles (WIMPs), a leading dark matter candidate. The goal of the LUX detector is to clearly detect (or exclude) WIMPS with a spin independent cross-section per nucleon of 2×10-46cm2, equivalent to ∼1event/100kg/month in the inner 100-kg fiducial volume (FV) of the 370-kg detector. The overall background goals are set to have <1 background events characterized as possible WIMPs in the FV in 300 days of running. This paper describes the design and construction of the LUX detector.

Radiogenic and Muon-Induced Backgrounds in the LUX Dark Matter Detector

Abstract 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 85.3xa0day WIMP search run is ( 2.6 ± 0.2 stat ± 0.4 sys ) × 10 - 3 events keV ee - 1 kg - 1 day - 1 in a 118xa0kg fiducial volume. The observed background rate is ( 3.6 ± 0.4 stat ) × 10 - 3 events keV ee - 1 kg - 1 day - 1 , consistent with model projections. The expectation for the radiogenic background in a subsequent one-year run is presented.

Technical results from the surface run of the LUX dark matter experiment

Abstract We present the results of the three-month above-ground commissioning run of the Large Underground Xenon (LUX) experiment at the Sanford Underground Research Facility located in Lead, South Dakota, USA. LUX is a 370xa0kg liquid xenon detector that will search for cold dark matter in the form of Weakly Interacting Massive Particles (WIMPs). The commissioning run, conducted with the detector immersed in a water tank, validated the integration of the various sub-systems in preparation for the underground deployment. Using the data collected, we report excellent light collection properties, achieving 8.4 photoelectrons per keV for 662xa0keV electron recoils without an applied electric field, measured in the center of the WIMP target. We also find good energy and position resolution in relatively high-energy interactions from a variety of internal and external sources. Finally, we have used the commissioning data to tune the optical properties of our simulation and report updated sensitivity projections for spin-independent WIMP-nucleon scattering.

Limits on spin-dependent WIMP-nucleon cross section obtained from the complete LUX exposure

We present experimental constraints on the spin-dependent WIMP-nucleon elastic cross sections from the total 129.5u2009u2009kgu2009yr exposure acquired by the Large Underground Xenon experiment (LUX), operating at the Sanford Underground Research Facility in Lead, South Dakota (USA). A profile likelihood ratio analysis allows 90%xa0C.L. upper limits to be set on the WIMP-neutron (WIMP-proton) cross section of σ_{n}=1.6×10^{-41}u2009u2009cm^{2} (σ_{p}=5×10^{-40}u2009u2009cm^{2}) at 35u2009u2009GeVu2009c^{-2}, almost a sixfold improvement over the previous LUX spin-dependent results. The spin-dependent WIMP-neutron limit is the most sensitive constraint to date.

An Ultra-Low Background PMT for Liquid Xenon Detectors

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.

Ultralow energy calibration of LUX detector using Xe127 electron capture

Author(s): Akerib, DS; Alsum, S; Araujo, HM; Bai, X; Bailey, AJ; Balajthy, J; Beltrame, P; Bernard, EP; Bernstein, A; Biesiadzinski, TP; Boulton, EM; Bras, P; Byram, D; Cahn, SB; Carmona-Benitez, MC; Chan, C; Currie, A; Cutter, JE; Davison, TJR; Dobi, A; Druszkiewicz, E; Edwards, BN; Fallon, SR; Fan, A; Fiorucci, S; Gaitskell, RJ; Genovesi, J; Ghag, C; Gilchriese, MGD; Hall, CR; Hanhardt, M; Haselschwardt, SJ; Hertel, SA; Hogan, DP; Horn, M; Huang, DQ; Ignarra, CM; Jacobsen, RG; Ji, W; Kamdin, K; Kazkaz, K; Khaitan, D; Knoche, R; Larsen, NA; Lenardo, BG; Lesko, KT; Lindote, A; Lopes, MI; Manalaysay, A; Mannino, RL; Marzioni, MF; McKinsey, DN; Mei, DM; Mock, J; Moongweluwan, M; Morad, JA; Murphy, ASJ; Nehrkorn, C; Nelson, HN; Neves, F; OSullivan, K; Oliver-Mallory, KC; Palladino, KJ; Pease, EK; Rhyne, C; Shaw, S; Shutt, TA; Silva, C; Solmaz, M; Solovov, VN; Sorensen, P; Sumner, TJ; Szydagis, M; Taylor, DJ; Taylor, WC; Tennyson, BP; Terman, PA; Tiedt, DR; To, WH; Tripathi, M; Tvrznikova, L; Uvarov, S; Velan, V; Verbus, JR; Webb, RC | Abstract:

Position reconstruction in LUX

Author(s): Akerib, DS; Alsum, S; Arauandjo, HM; Bai, X; Bailey, AJ; Balajthy, J; Beltrame, P; Bernard, EP; Bernstein, A; Biesiadzinski, TP; Boulton, EM; Braands, P; Byram, D; Cahn, SB; Carmona-Benitez, MC; Chan, C; Currie, A; Cutter, JE; Davison, TJR; Dobi, A; Druszkiewicz, E; Edwards, BN; Fallon, SR; Fan, A; Fiorucci, S; Gaitskell, RJ; Genovesi, J; Ghag, C; Gilchriese, MGD; Hall, CR; Hanhardt, M; Haselschwardt, SJ; Hertel, SA; Hogan, DP; Horn, M; Huang, DQ; Ignarra, CM; Jacobsen, RG; Ji, W; Kamdin, K; Kazkaz, K; Khaitan, D; Knoche, R; Larsen, NA; Lenardo, BG; Lesko, KT; Lindote, A; Lopes, MI; Manalaysay, A; Mannino, RL; Marzioni, MF; McKinsey, DN; Mei, DM; Mock, J; Moongweluwan, M; Morad, JA; Murphy, ASJ; Nehrkorn, C; Nelson, HN; Neves, F; OSullivan, K; Oliver-Mallory, KC; Palladino, KJ; Pease, EK; Rhyne, C; Shaw, S; Shutt, TA; Silva, C; Solmaz, M; Solovov, VN; Sorensen, P; Sumner, TJ; Szydagis, M; Taylor, DJ; Taylor, WC; Tennyson, BP; Terman, PA; Tiedt, DR; To, WH; Tripathi, M; Tvrznikova, L; Uvarov, S; Velan, V; Verbus, JR; Webb, RC | Abstract:

Chromatographic separation of radioactive noble gases from xenon

Abstract The Large Underground Xenon (LUX) experiment operates at the Sanford Underground Research Facility to detect nuclear recoils from the hypothetical Weakly Interacting Massive Particles (WIMPs) on a liquid xenon target. Liquid xenon typically contains trace amounts of the noble radioactive isotopes 85Kr and 39Ar that are not removed by the in situ gas purification system. The decays of these isotopes at concentrations typical of research-grade xenon would be a dominant background for a WIMP search experiment. To remove these impurities from the liquid xenon, a chromatographic separation system based on adsorption on activated charcoal was built. 400xa0kg of xenon was processed, reducing the average concentration of krypton from 130xa0ppb to 3.5xa0ppt as measured by a cold-trap assisted mass spectroscopy system. A 50 kg batch spiked to 0.001 g/g of krypton was processed twice and reduced to an upper limit of 0.2 ppt.

Kr83m calibration of the 2013 LUX dark matter search

Author(s): Akerib, DS; Alsum, S; Araujo, HM; Bai, X; Bailey, AJ; Balajthy, J; Beltrame, P; Bernard, EP; Bernstein, A; Biesiadzinski, TP; Boulton, EM; Bras, P; Byram, D; Cahn, SB; Carmona-Benitez, MC; Chan, C; Currie, A; Cutter, JE; Davison, TJR; Dobi, A; Druszkiewicz, E; Edwards, BN; Fallon, SR; Fan, A; Fiorucci, S; Gaitskell, RJ; Genovesi, J; Ghag, C; Gilchriese, MGD; Hall, CR; Hanhardt, M; Haselschwardt, SJ; Hertel, SA; Hogan, DP; Horn, M; Huang, DQ; Ignarra, CM; Jacobsen, RG; Ji, W; Kamdin, K; Kazkaz, K; Khaitan, D; Knoche, R; Larsen, NA; Lenardo, BG; Lesko, KT; Lindote, A; Lopes, MI; Manalaysay, A; Mannino, RL; Marzioni, MF; McKinsey, DN; Mei, DM; Mock, J; Moongweluwan, M; Morad, JA; Murphy, ASJ; Nehrkorn, C; Nelson, HN; Neves, F; OSullivan, K; Oliver-Mallory, KC; Palladino, KJ; Pease, EK; Rhyne, C; Shaw, S; Shutt, TA; Silva, C; Solmaz, M; Solovov, VN; Sorensen, P; Sumner, TJ; Szydagis, M; Taylor, DJ; Taylor, WC; Tennyson, BP; Terman, PA; Tiedt, DR; To, WH; Tripathi, M; Tvrznikova, L; Uvarov, S; Velan, V; Verbus, JR; Webb, RC | Abstract: