Publications
90 results found
Aalbers J, Akerib DS, Al Musalhi AK, et al., 2023, Search for new physics in low-energy electron recoils from the first LZ exposure, PHYSICAL REVIEW D, Vol: 108, ISSN: 2470-0010
Aalbers J, Akerib DS, Akerlof CW, et al., 2023, First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment, PHYSICAL REVIEW LETTERS, Vol: 131, ISSN: 0031-9007
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- Citations: 5
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
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- Citations: 1
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, 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.
Collaboration S, Abreu Y, Amhis Y, et al., 2021, SoLid: A short baseline reactor neutrino experiment, Journal of Instrumentation, Vol: 16, Pages: 1-37, ISSN: 1748-0221
The SoLid experiment, short for Search for Oscillations with a Lithium-6detector, is a new generation neutrino experiment which tries to address thekey challenges for high precision reactor neutrino measurements at very shortdistances from a reactor core and with little or no overburden. The primarygoal of the SoLid experiment is to perform a precise measurement of theelectron antineutrino energy spectrum and flux and to search for very shortdistance neutrino oscillations as a probe of eV-scale sterile neutrinos. Thispaper describes the SoLid detection principle, the mechanical design and theconstruction of the detector. It then reports on the installation andcommissioning on site near the BR2 reactor, Belgium, and finally highlights itsperformance in terms of detector response and calibration.
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.
Griffiths J, Kleinegesse S, Saunders D, et al., 2020, Pulse shape discrimination and exploration of scintillation signals using convolutional neural networks, MACHINE LEARNING-SCIENCE AND TECHNOLOGY, Vol: 1
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- Citations: 15
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, 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, 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.
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.
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.
Abreu Y, Amhis Y, Ban G, et al., 2019, Development of a quality assurance process for the SoLid experiment, Journal of Instrumentation, Vol: 14, Pages: 1-24, ISSN: 1748-0221
The SoLid experiment has been designed to search for an oscillation pattern induced by a light sterile neutrino state, utilising the BR2 reactor of SCK⋅CEN, in Belgium. The detector leverages a new hybrid technology, utilising two distinct scintillators in a cubic array, creating a highly segmented detector volume. A combination of 5 cm cubic polyvinyltoluene cells, with 6LiF:ZnS(Ag) sheets on two faces of each cube, facilitate reconstruction of the neutrino signals. Whilst the high granularity provides a powerful toolset to discriminate backgrounds; by itself the segmentation also represents a challenge in terms of homogeneity and calibration, for a consistent detector response. The search for this light sterile neutrino implies a sensitivity to distortions of around Script O(10)% in the energy spectrum of reactor bar nue. Hence, a very good neutron detection efficiency, light yield and homogeneous detector response are critical for data validation. The minimal requirements for the SoLid physics program are a light yield and a neutron detection efficiency larger than 40 PA/MeV/cube and 50% respectively. In order to guarantee these minimal requirements, the collaboration developed a rigorous quality assurance process for all 12800 cubic cells of the detector. To carry out the quality assurance process, an automated calibration system called CALIPSO was designed and constructed. CALIPSO provides precise, automatic placement of radioactive sources in front of each cube of a given detector plane (16×16 cubes). A combination of 22Na, 252Cf and AmBe gamma and neutron sources were used by CALIPSO during the quality assurance process. Initially, the scanning identified defective components allowing for repair during initial construction of the SoLid detector. Secondly, a full analysis of the calibration data revealed initial estimations for the light yield of over 60 PA/MeV and neutron reconstruction efficiency of 68%, validating the SoLid physics requirements.
Carr R, Coleman J, Danilov M, et al., 2019, Neutrino-Based Tools for Nuclear Verification and Diplomacy in North Korea, SCIENCE & GLOBAL SECURITY, Vol: 27, Pages: 15-28, ISSN: 0892-9882
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- Citations: 6
Bauer D, Colling D, Fayer S, et al., 2019, The LZ UK Data Centre, 23rd International Conference on Computing in High Energy and Nuclear Physics (CHEP), Publisher: E D P SCIENCES, ISSN: 2100-014X
Dell'Acqua A, Aduszkiewicz A, Ahlers M, et al., 2018, Future Opportunities in Accelerator-based Neutrino Physics
This document summarizes the conclusions of the Neutrino Town Meeting held atCERN in October 2018 to review the neutrino field at large with the aim ofdefining a strategy for accelerator-based neutrino physics in Europe. Theimportance of the field across its many complementary components is stressed.Recommendations are presented regarding the accelerator based neutrino physics,pertinent to the European Strategy for Particle Physics. We address inparticular i) the role of CERN and its neutrino platform, ii) the importance ofancillary neutrino cross-section experiments, and iii) the capability of fixedtarget experiments as well as present and future high energy colliders tosearch for the possible manifestations of neutrino mass generation mechanisms.
Abreu Y, Amhis Y, Ban G, et al., 2018, Commissioning and operation of the readout system for the solid neutrino detector
The SoLid experiment aims to measure neutrino oscillation at a baseline of6.4 m from the BR2 nuclear reactor in Belgium. Anti-neutrinos interact viainverse beta decay (IBD), resulting in a positron and neutron signal that arecorrelated in time and space. The detector operates in a surface building, withmodest shielding, and relies on extremely efficient online rejection ofbackgrounds in order to identify these interactions. A novel detector designhas been developed using 12800 5 cm cubes for high segmentation. Each cube isformed of a sandwich of two scintillators, PVT and 6LiF:ZnS(Ag), allowing thedetection and identification of positrons and neutrons respectively. The activevolume of the detector is an array of cubes measuring 80x80x250 cm(corresponding to a fiducial mass of 1.6 T), which is read out in layers usingtwo dimensional arrays of wavelength shifting fibres and siliconphotomultipliers, for a total of 3200 readout channels. Signals are recordedwith 14 bit resolution, and at 40 MHz sampling frequency, for a total raw datarate of over 2 Tbit/s. In this paper, we describe a novel readout and triggersystem built for the experiment, that satisfies requirements on: compactness,low power, high performance, and very low cost per channel. The system uses acombination of high price-performance FPGAs with a gigabit Ethernet basedreadout system, and its total power consumption is under 1 kW. The use of zerosuppression techniques, combined with pulse shape discrimination triggeralgorithms to detect neutrons, results in an online data reduction factor ofaround 10000. The neutron trigger is combined with a large per-channel historytime buffer, allowing for unbiased positron detection. The system wascommissioned in late 2017, with successful physics data taking established inearly 2018.
Carr R, Coleman J, Gratta G, et al., 2018, Neutrino physics for Korean diplomacy, SCIENCE, Vol: 362, Pages: 649-650, ISSN: 0036-8075
Paredes BL, Araujo HM, Froborg E, et al., 2018, Response of photomultiplier tubes to xenon scintillation light, Astroparticle Physics, Vol: 102, Pages: 56-66, ISSN: 0927-6505
We present the precision calibration of 35 Hamamatsu R11410-22 photomultiplier tubes (PMTs) with xenon scintillation light centred near 175 nm. This particular PMT variant was developed specifically for the LUX-ZEPLIN (LZ) dark matter experiment. A room-temperature xenon scintillation cell coupled to a vacuum cryostat was used to study the full-face PMT response at both room and low temperature ( ∼ −100 °C), in particular to determine the quantum efficiency (QE) and double photoelectron emission (DPE) probability in LZ operating conditions. For our sample with an average QE of (32.4 ± 2.9)% at room temperature, we find a relative improvement of (17.9 ± 5.2)% upon cooling (where uncertainty values refer to the sample standard deviation). The mean DPE probability in response to single vacuum ultraviolet (VUV) photons is (22.6 ± 2.0)% at low temperature; the DPE increase relative to room temperature, measured here for the first time, was (12.2 ± 3.9)%. Evidence of a small triple photoelectron emission probability ( ∼ 0.6%) has also been observed. Useful correlations are established between these parameters and the QE as measured by the manufacturer. The single VUV photon response is also measured for one ETEL D730/9829QB, a PMT with a more standard bialkali photocathode used in the ZEPLIN-III experiment, for which we obtained a cold DPE fraction of (9.1 ± 0.1)%. Hence, we confirm that this effect is not restricted to the low-temperature bialkali photocathode technology employed by Hamamatsu. This highlights the importance of considering this phenomenon in the interpretation of data from liquid xenon scintillation and electroluminescence detectors, and from many other optical measurements in this wavelength region.
Abreu Y, Amhis Y, Beaumont W, et al., 2018, Optimisation of the scintillation light collection and uniformity for the SoLid experiment, ISSN: 1748-0221
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