Publications
177 results found
Wass PJ, Sumner TJ, Araújo HM, et al., 2023, Simulating the charging of isolated free-falling masses from TeV to eV energies: Detailed comparison with LISA Pathfinder results, Physical Review D, Vol: 107, ISSN: 2470-0010
A model is presented that explains the charging rate of the LISA Pathfinder test masses by the interplanetary cosmic ray environment. The model incorporates particle-tracking from TeV to eV energies using a combination of geant4 and a custom low-energy particle generation and tracking code. The electrostatic environment of the test mass is simulated allowing for a comparison of the test-mass charging-rate dependence on local electric fields with observations made in orbit. The model is able to reproduce the observed charging behavior with good accuracy using gold surface properties compatible with literature values. The results of the model confirm that a significant fraction of the net charging current is caused by a population of low-energy (∼eV) electrons produced by electron- and ion-induced kinetic emission from the test mass and surrounding metal surfaces. Assuming a gold work function of 4.2 eV, the unbalanced flow of these electrons to and from the unbiased test mass contributes ∼10% of the overall test mass charging rate. Their contribution to the charging-current shot noise is disproportionately higher, and it adds ∼40% to the overall predicted noise. However, even with this increased noise contribution, the overall charging-current noise is still only 40% of that measured in-orbit, and this remains an unsolved issue.
Aalbers J, AbdusSalam SS, Abe K, et al., 2023, A next-generation liquid xenon observatory for dark matter and neutrino physics, JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS, Vol: 50, ISSN: 0954-3899
- Author Web Link
- Cite
- Citations: 1
Alonso I, Alpigiani C, Altschul B, et al., 2022, Cold atoms in space: community workshop summary and proposed road-map, EPJ QUANTUM TECHNOLOGY, Vol: 9, ISSN: 2662-4400
Akerib DS, Alsum S, Araujo HM, et al., 2022, Fast and flexible analysis of direct dark matter search data with machine learning, PHYSICAL REVIEW D, Vol: 106, ISSN: 2470-0010
Linehan R, Mannino RL, Fan A, et al., 2022, Design and production of the high voltage electrode grids and electron extraction region for the LZ dual-phase xenon time projection chamber, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 1031, ISSN: 0168-9002
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.
Aalbers J, Akerib DS, Al Musalhi AK, et al., 2022, Cosmogenic production of 37Ar in the context of the LUX-ZEPLIN experiment, Physical Review D, Vol: 105, Pages: 1-8, ISSN: 2470-0010
We estimate the amount of 37Ar produced in natural xenon via cosmic-ray-induced spallation, an inevitable consequence of the transportation and storage of xenon on the Earth’s surface. We then calculate the resulting 37Ar concentration in a 10-tonne payload (similar to that of the LUX-ZEPLIN experiment) assuming a representative schedule of xenon purification, storage, and delivery to the underground facility. Using the spallation model by Silberberg and Tsao, the sea-level production rate of 37Ar in natural xenon is estimated to be 0.024 atoms/kg/day. Assuming the xenon is successively purified to remove radioactive contaminants in 1-tonne batches at a rate of 1 tonne/month, the average 37Ar activity after 10 tons are purified and transported underground is 0.058−0.090 μBq/kg, depending on the degree of argon removal during above-ground purification. Such cosmogenic 37Ar will appear as a noticeable background in the early science data, while decaying with a 35-day half-life. This newly noticed production mechanism of 37Ar should be considered when planning for future liquid-xenon-based experiments.
Akerib DS, Akerlof CW, Akimov DY, et al., 2022, The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs (vol 80, 1044, 2020), EUROPEAN PHYSICAL JOURNAL C, Vol: 82, ISSN: 1434-6044
Akerib DS, Al Musalhi AK, Alsum SK, et al., 2021, Projected sensitivities of the LUX-ZEPLIN experiment to new physics via low-energy electron recoils, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-16, ISSN: 1550-2368
LUX-ZEPLIN is a dark matter detector expected to obtain world-leading sensitivity to weakly-interacting massive particles interacting via nuclear recoils with a ∼7-tonne xenon target mass. This paper presents sensitivity projections to several low-energy signals of the complementary electron recoil signal type: 1) an effective neutrino magnetic moment, and 2) an effective neutrino millicharge, both for pp-chain solar neutrinos, 3) an axion flux generated by the Sun, 4) axionlike particles forming the Galactic dark matter, 5) hidden photons, 6) mirror dark matter, and 7) leptophilic dark matter. World-leading sensitivities are expected in each case, a result of the large 5.6 t 1000 d exposure and low expected rate of electron-recoil backgrounds in the <100 keV energy regime. A consistent signal generation, background model and profile-likelihood analysis framework is used throughout.
Akerib DS, Al Musalhi AK, Alsum SK, et al., 2021, Projected sensitivity of the LUX-ZEPLIN experiment to the two-neutrino and neutrinoless double β decays of Xe134, Physical Review C, Vol: 104, Pages: 1-11, ISSN: 2469-9985
The projected sensitivity of the LUX-ZEPLIN (LZ) experiment to two-neutrino and neutrinoless double β decay of 134Xe is presented. LZ is a 10-tonne xenon time-projection chamber optimized for the detection of dark matter particles and is expected to start operating in 2021 at Sanford Underground Research Facility, USA. Its large mass of natural xenon provides an exceptional opportunity to search for the double β decay of 134Xe, for which xenon detectors enriched in 136Xe are less effective. For the two-neutrino decay mode, LZ is predicted to exclude values of the half-life up to 1.7×1024 years at 90% confidence level (CL) and has a three-sigma observation potential of 8.7×1023 years, approaching the predictions of nuclear models. For the neutrinoless decay mode LZ, is projected to exclude values of the half-life up to 7.3×1024 years at 90% CL.
Akerib DS, Alsum S, Araujo HM, et al., 2021, Constraints on effective field theory couplings using 311.2 days of LUX data, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-19, ISSN: 1550-2368
We report here the results of a nonrelativistic effective field theory (EFT) WIMP search analysis using LUX data. We build upon previous LUX analyses by extending the search window to include nuclear recoil energies up to ∼180 keVnr, requiring a reassessment of data quality criteria and background models. In order to use an unbinned profile likelihood statistical framework, the development of new analysis techniques to account for higher-energy backgrounds was required. With a 3.14×104 kg⋅day exposure using data collected between 2014 and 2016, we find our data is compatible with the background expectation and set 90% C.L. exclusion limits on nonrelativistic EFT WIMP-nucleon couplings, improving upon previous LUX results and providing constraints on a EFT WIMP interactions using the {neutron,proton} interaction basis. Additionally, we report exclusion limits on inelastic EFT WIMP-isoscalar recoils that are competitive and world-leading for several interaction operators.
Akerib DS, Alsum S, Araujo HM, et al., 2021, Improving sensitivity to low-mass dark matter in LUX using a novel electrode background mitigation technique, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 104, Pages: 1-15, ISSN: 1550-2368
This paper presents a novel technique for mitigating electrode backgrounds that limit the sensitivity of searches for low-mass dark matter (DM) using xenon time projection chambers. In the Large Underground Xenon (LUX) detector, signatures of low-mass DM interactions would be very low-energy (∼keV) scatters in the active target that ionize only a few xenon atoms and seldom produce detectable scintillation signals. In this regime, extra precaution is required to reject a complex set of low-energy electron backgrounds that have long been observed in this class of detector. Noticing backgrounds from the wire grid electrodes near the top and bottom of the active target are particularly pernicious, we develop a machine learning technique based on ionization pulse shape to identify and reject these events. We demonstrate the technique can improve Poisson limits on low-mass DM interactions by a factor of 1.7–3 with improvement depending heavily on the size of ionization signals. We use the technique on events in an effective 5 tonne·day exposure from LUX’s 2013 science operation to place strong limits on low-mass DM particles with masses in the range mχ∈0.15–10 GeV. This machine learning technique is expected to be useful for near-future experiments, such as LUX-ZEPLIN and XENONnT, which hope to perform low-mass DM searches with the stringent background control necessary to make a discovery.
Akerib DS, Alsum S, Araujo HM, et al., 2020, Discrimination of electronic recoils from nuclear recoils in two-phase xenon time projection chambers, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 1-27, ISSN: 1550-2368
We present a comprehensive analysis of electronic recoil vs nuclear recoil discrimination in liquid/gas xenon time projection chambers, using calibration data from the 2013 and 2014–2016 runs of the Large Underground Xenon experiment. We observe strong charge-to-light discrimination enhancement with increased event energy. For events with S1=120 detected photons, i.e., equivalent to a nuclear recoil energy of ∼100 keV, we observe an electronic recoil background acceptance of <10−5 at a nuclear recoil signal acceptance of 50%. We also observe modest electric field dependence of the discrimination power, which peaks at a field of around 300 V/cm over the range of fields explored in this study (50–500 V/cm). In the weakly interacting massive particle search region of S1=1−80 phd, the minimum electronic recoil leakage we observe is (7.3±0.6)×10−4, which is obtained for a drift field of 240–290 V/cm. Pulse shape discrimination is utilized to improve our results, and we find that, at low energies and low fields, there is an additional reduction in background leakage by a factor of up to 3. We develop an empirical model for recombination fluctuations which, when used alongside the Noble Element Scintillation Technique simulation package, correctly reproduces the skewness of the electronic recoil data. We use this updated simulation to study the width of the electronic recoil band, finding that its dominant contribution comes from electron-ion recombination fluctuations, followed in magnitude of contribution by fluctuations in the S1 signal, fluctuations in the S2 signal, and fluctuations in the total number of quanta produced for a given energy deposition.
Akerib DS, Akerlof CW, Akimov DY, et al., 2020, The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs, European Physical Journal C: Particles and Fields, Vol: 80, Pages: 1-52, ISSN: 1124-1861
LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above 1.4×10−48cm2 for a WIMP mass of 40GeV/c2 and a 1000days exposure. LZ achieves this sensitivity through a combination of a large 5.6t fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented.
Akerib DS, Alsum S, Araujo HM, et al., 2020, Investigation of background electron emission in the LUX detector, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 102, Pages: 1-17, ISSN: 1550-2368
Dual-phase xenon detectors, as currently used in direct detection dark matter experiments, have observed elevated rates of background electron events in the low energy region. While this background negatively impacts detector performance in various ways, its origins have only been partially studied. In this paper we report a systematic investigation of the electron pathologies observed in the LUX dark matter experiment. We characterize different electron populations based on their emission intensities and their correlations with preceding energy depositions in the detector. By studying the background under different experimental conditions, we identified the leading emission mechanisms, including photoionization and the photoelectric effect induced by the xenon luminescence, delayed emission of electrons trapped under the liquid surface, capture and release of drifting electrons by impurities, and grid electron emission. We discuss how these backgrounds can be mitigated in LUX and future xenon-based dark matter experiments.
Akerib DS, Alsum S, Araujo HM, et al., 2020, Search for two neutrino double electron capture of(124)Xe and(126)Xe in the full exposure of the LUX detector, Journal of Physics G: Nuclear and Particle Physics, Vol: 47, Pages: 1-13, ISSN: 0954-3899
Two-neutrino double electron capture is a process allowed in the standard model of particle physics. This rare decay has been observed in 78Kr, 130Ba and more recently in 124Xe. In this publication we report on the search for this process in 124Xe and 126Xe using the full exposure of the large underground xenon (LUX) experiment, in a total of 27769.5 kg-days. No evidence of a signal was observed, allowing us to set 90% C.L. lower limits for the half-lives of these decays of 2.0 × 1021 years for 124Xe and 1.9 × 1021 years for 126Xe.
Akerib DS, Akerlof CW, Alqahtani A, et al., 2020, Projected sensitivity of the LUX-ZEPLIN experiment to the 0νββ decay of 136Xe, Physical Review C, Vol: 102, Pages: 014602 – 1-014602 – 13, ISSN: 2469-9985
The LUX-ZEPLIN (LZ) experiment will enable a neutrinoless double β decay search in parallel to the main science goal of discovering dark matter particle interactions. We report the expected LZ sensitivity to 136Xe neutrinoless double β decay, taking advantage of the significant (>600 kg) 136Xe mass contained within the active volume of LZ without isotopic enrichment. After 1000 live-days, the median exclusion sensitivity to the half-life of 136Xe is projected to be 1.06×1026 years (90% confidence level), similar to existing constraints. We also report the expected sensitivity of a possible subsequent dedicated exposure using 90% enrichment with 136Xe at 1.06×1027 years.
Araújo H, 2020, Revised performance parameters of the ZEPLIN-III dark matter experiment, Publisher: arXiv
This note presents revised detector parameters applicable to data from theFirst Science Run of the ZEPLIN-III dark matter experiment; these datasets wereacquired in 2008 and reanalised in 2011. This run demonstrated electron recoildiscrimination in liquid xenon at the level of 1 part in 10,000 below 40 keVnuclear recoil energy, at an electric field of 3.8 kV/cm; this remains the bestdiscrimination reported for this medium to date. Building on relevantmeasurements published in recent years, the calibration of the scintillationand ionisation responses for both electron and nuclear recoils, which had beenmapped linearly to Co-57 gamma-ray interactions, is converted here into opticalparameters which are better suited to relate the data to the emerging liquidxenon response models. Additional information is given on the fitting of theelectron and nuclear recoil populations at low energy. The aim of this note isto support the further development of these models with valuable data acquiredat high field.
Collaboration TLUX-ZEPLIN, Akerib DS, Akerlof CW, et al., 2020, Simulations of Events for the LUX-ZEPLIN (LZ) Dark Matter Experiment, Astroparticle Physics, ISSN: 0927-6505
The LUX-ZEPLIN dark matter search aims to achieve a sensitivity to theWIMP-nucleon spin-independent cross-section down to (1-2) $\times$ $10^{-12}$pb at a WIMP mass of 40 GeV/$c^2$. This paper describes the simulationsframework that, along with radioactivity measurements, was used to support thisprojection, and also to provide mock data for validating reconstruction andanalysis software. Of particular note are the event generators, which allow usto model the background radiation, and the detector response physics used inthe production of raw signals, which can be converted into digitized waveformssimilar to data from the operational detector. Inclusion of the detectorresponse allows us to process simulated data using the same analysis routinesas developed to process the experimental data.
Akerib DS, Alsum S, Araújo HM, et al., 2020, An effective field theory analysis of the first LUX dark matter search, Publisher: arXiv
The Large Underground Xenon (LUX) dark matter search was a 250-kg active massdual-phase time projection chamber that operated by detecting light andionization signals from particles incident on a xenon target. In December 2015,LUX reported a minimum 90% upper C.L. of 6e-46 cm^2 on the spin-independentWIMP-nucleon elastic scattering cross section based on a 1.4e4 kg*day exposurein its first science run. Tension between experiments and the absence of adefinitive positive detection suggest it would be prudent to search for WIMPsoutside the standard spin-independent/spin-dependent paradigm. Recenttheoretical work has identified a complete basis of 14 independent effectivefield theory (EFT) operators to describe WIMP-nucleon interactions. In additionto spin-independent and spin-dependent nuclear responses, these operators canproduce novel responses such as angular-momentum-dependent and spin-orbitcouplings. Here we report on a search for all 14 of these EFT couplings withdata from LUX's first science run. Limits are placed on each coupling as afunction of WIMP mass.
El-Neaj YA, Alpigiani C, Amairi-Pyka S, et al., 2020, AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space, EPJ QUANTUM TECHNOLOGY, Vol: 7, ISSN: 2662-4400
Akerib DS, Akerlof CW, Alsum SK, et al., 2020, Projected WIMP sensitivity of the LUX-ZEPLIN dark matter experiment, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 101, Pages: 1-17, ISSN: 1550-2368
LUX-ZEPLIN (LZ) is a next-generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with weakly interacting massive particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6-tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above 1.4×10−48 cm2 for a 40 GeV/c2 mass WIMP. Additionally, a 5σ discovery potential is projected, reaching cross sections below the exclusion limits of recent experiments. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of 2.3×10−43 cm2 (7.1×10−42 cm2) for a 40 GeV/c2 mass WIMP is expected. With underground installation well underway, LZ is on track for commissioning at SURF in 2020.
Akerib DS, Akerlof CW, Alsum SK, et al., 2020, Measurement of the gamma ray background in the Davis cavern at the Sanford Underground Research Facility, Astroparticle Physics, Vol: 116, Pages: 1-10, ISSN: 0927-6505
Deep underground environments are ideal for low background searches due to the attenuation of cosmic rays by passage through the earth. However, they are affected by backgrounds from γ-rays emitted by 40K and the 238U and 232Th decay chains in the surrounding rock. The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a liquid xenon TPC located within the Davis campus at the Sanford Underground Research Facility, Lead, South Dakota, at the 4850-foot level. In order to characterise the cavern background, in-situ γ-ray measurements were taken with a sodium iodide detector in various locations and with lead shielding. The integral count rates (0–3300 keV) varied from 596 Hz to 1355 Hz for unshielded measurements, corresponding to a total flux from the cavern walls of 1.9 ± 0.4 γ cms. The resulting activity in the walls of the cavern can be characterised as 220 ± 60 Bq/kg of 40K, 29 ± 15 Bq/kg of 238U, and 13 ± 3 Bq/kg of 232Th.
Collaboration TLUX, Akerib DS, Alsum S, et al., 2020, Improved modeling of $β$ electronic recoils in liquid xenon using LUX calibration data, Journal of Instrumentation, ISSN: 1748-0221
We report here methods and techniques for creating and improving a model thatreproduces the scintillation and ionization response of a dual-phase liquid andgaseous xenon time-projection chamber. Starting with the recent release of theNoble Element Simulation Technique (NEST v2.0), electronic recoil data from the$\beta$ decays of ${}^3$H and ${}^{14}$C in the Large Underground Xenon (LUX)detector were used to tune the model, in addition to external data sets thatallow for extrapolation beyond the LUX data-taking conditions. This paper alsopresents techniques used for modeling complicated temporal and spatial detectorpathologies that can adversely affect data using a simplified model framework.The methods outlined in this report show an example of the robust applicationspossible with NEST v2.0, while also providing the final electronic recoil modeland detector parameters that will used in the new analysis package, the LUXLegacy Analysis Monte Carlo Application (LLAMA), for accurate reproduction ofthe LUX data. As accurate background reproduction is crucial for the success ofrare-event searches, such as dark matter direct detection experiments, thetechniques outlined here can be used in other single-phase and dual-phase xenondetectors to assist with accurate ER background reproduction.
Akerib DS, Akerlof CW, Akimov DY, et al., 2020, The LUX-ZEPLIN (LZ) experiment, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment, Vol: 953, Pages: 1-22, ISSN: 0168-9002
We describe the design and assembly of the LUX-ZEPLIN experiment, a direct detection search for cosmic WIMP dark matter particles. The centerpiece of the experiment is a large liquid xenon time projection chamber sensitive to low energy nuclear recoils. Rejection of backgrounds is enhanced by a Xe skin veto detector and by a liquid scintillator Outer Detector loaded with gadolinium for efficient neutron capture and tagging. LZ is located in the Davis Cavern at the 4850’ level of the Sanford Underground Research Facility in Lead, South Dakota, USA. We describe the major subsystems of the experiment and its key design features and requirements.
Akerib DS, Alsum S, Araujo HM, et al., 2020, Extending light WIMP searches to single scintillation photons in LUX, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 101, Pages: 1-11, ISSN: 1550-2368
We present a novel analysis technique for liquid xenon time projection chambers that allows for a lower threshold by relying on events with a prompt scintillation signal consisting of single detected photons. The energy threshold of the LUX dark matter experiment is primarily determined by the smallest scintillation response detectable, which previously required a twofold coincidence signal in its photomultiplier arrays, enforced in data analysis. The technique presented here exploits the double photoelectron emission effect observed in some photomultiplier models at vacuum ultraviolet wavelengths. We demonstrate this analysis using an electron recoil calibration dataset and place new constraints on the spin-independent scattering cross section of weakly interacting massive particles (WIMPs) down to 2.5 GeV/c2 WIMP mass using the 2013 LUX dataset. This new technique is promising to enhance light WIMP and astrophysical neutrino searches in next-generation liquid xenon experiments.
Akerib DS, Alsum S, Araujo HM, et al., 2020, First direct detection constraint on mirror dark matter kinetic mixing using LUX 2013 data, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 101, Pages: 012003 – 1-012003 – 8, ISSN: 1550-2368
We present the results of a direct detection search for mirror dark matter interactions, using data collected from the Large Underground Xenon experiment during 2013, with an exposure of 95 live−days×118 kg. Here, the calculations of the mirror electron scattering rate in liquid xenon take into account the shielding effects from mirror dark matter captured within the Earth. Annual and diurnal modulation of the dark matter flux and atomic shell effects in xenon are also accounted for. Having found no evidence for an electron recoil signal induced by mirror dark matter interactions we place an upper limit on the kinetic mixing parameter over a range of local mirror electron temperatures between 0.1 and 0.9 keV. This limit shows significant improvement over the previous experimental constraint from orthopositronium decays and significantly reduces the allowed parameter space for the model. We exclude mirror electron temperatures above 0.3 keV at a 90% confidence level, for this model, and constrain the kinetic mixing below this temperature.
Akerib DS, Alsum S, Araujo HM, et al., 2019, Improved measurements of the beta-decay response of liquid xenon with the LUX detector, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 100, ISSN: 1550-2368
We report results from an extensive set of measurements of the β-decay response in liquid xenon. These measurements are derived from high-statistics calibration data from injected sources of both 3H and 14C in the LUX detector. The mean light-to-charge ratio is reported for 13 electric field values ranging from 43 to 491 V/cm, and for energies ranging from 1.5 to 145 keV.
Akerib DS, Alsum S, Araujo HM, et al., 2019, Results of a search for sub-GeV Dark Matter using 2013 LUX data, Physical Review Letters, Vol: 122, ISSN: 0031-9007
The scattering of dark matter (DM) particles with sub-GeV masses off nuclei is difficult to detect using liquid xenon-based DM search instruments because the energy transfer during nuclear recoils is smaller than the typical detector threshold. However, the tree-level DM-nucleus scattering diagram can be accompanied by simultaneous emission of a bremsstrahlung photon or a so-called “Migdal” electron. These provide an electron recoil component to the experimental signature at higher energies than the corresponding nuclear recoil. The presence of this signature allows liquid xenon detectors to use both the scintillation and the ionization signals in the analysis where the nuclear recoil signal would not be otherwise visible. We report constraints on spin-independent DM-nucleon scattering for DM particles with masses of 0.4–5 GeV/c2 using 1.4×104 kg day of search exposure from the 2013 data from the Large Underground Xenon (LUX) experiment for four different classes of mediators. This analysis extends the reach of liquid xenon-based DM search instruments to lower DM masses than has been achieved previously.
Tomás A, Araújo HM, Bailey AJ, et al., 2018, Study and mitigation of spurious electron emission from cathodic wires in noble liquid time projection chambers, Astroparticle Physics, Vol: 103, Pages: 49-61, ISSN: 0927-6505
Noble liquid radiation detectors have long been afflicted by spurious electron emission from their cathodic electrodes. This phenomenon must be understood and mitigated in the next generation of liquid xenon (LXe) experiments searching for WIMP dark matter or neutrinoless double beta decay, and in the large liquid argon (LAr) detectors for the long-baseline neutrino programmes. We present a systematic study of this spurious emission involving a series of slow voltage-ramping tests on fine metal wires immersed in a two-phase xenon time projection chamber with single electron sensitivity. Emission currents as low as 10−18A can thus be detected by electron counting, a vast improvement over previous dedicated measurements. Emission episodes were recorded at surface fields as low as ∼ 10 kV/cm in some wires and observed to have complex emission patterns, with average rates of 10–200 counts per second (c/s) and outbreaks as high as ∼ 106c/s. A fainter, less variable type of emission was also present in all untreated samples. There is evidence of a partial conditioning effect, with subsequent tests yielding on average fewer emitters occurring at different fields for the same wire. We find no evidence for an intrinsic threshold particular to the metal-LXe interface which might have limited previous experiments up to fields of at least 160 kV/cm. The general phenomenology is not consistent with enhanced field emission from microscopic filaments, but it appears instead to be related to the quality of the wire surface in terms of corrosion and the nature of its oxide layer. This study concludes that some surface treatments, in particular nitric acid cleaning applied to stainless steel wires, can bring about at least order-of-magnitude improvements in overall electron emission rates, and this should help the next generation of detectors achieve the required electrostatic performance.
Akerib DS, Alsum S, Araujo HM, et al., 2018, LUX trigger efficiency, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 908, Pages: 401-410, ISSN: 0168-9002
The Large Underground Xenon experiment (LUX) searches for dark matter using a dual-phase xenon detector. LUX uses a custom-developed trigger system for event selection. In this paper, the trigger efficiency, which is defined as the probability that an event of interest is selected for offline analysis, is studied using raw data obtained from both electron recoil (ER) and nuclear recoil (NR) calibrations. The measured efficiency exceeds 98% at a pulse area of 90 detected photons, which is well below the WIMP analysis threshold on the S2 pulse area. The efficiency also exceeds 98% at recoil energies of 0.2 keV and above for ER, and 1.3 keV and above for NR. The measured trigger efficiency varies between 99% and 100% over the fiducial volume of the detector.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.