Publications
173 results found
Bradley A, Akerib DS, Araujo HM, et al., 2015, Radon-Related Backgrounds in the LUX Dark Matter Search, 13th International Conference on Topics in Astroparticle and Underground Physics (TAUP), Publisher: ELSEVIER SCIENCE BV, Pages: 658-665, ISSN: 1875-3892
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- Citations: 8
Mitchell EF, Araujo HM, Daly E, et al., 2014, The highly miniaturised radiation monitor, Journal of Instrumentation, Vol: 9, ISSN: 1748-0221
We present the design and preliminary calibration results of a novel highly miniaturised particle radiation monitor (HMRM) for spacecraft use. The HMRM device comprises a telescopic configuration of active pixel sensors enclosed in a titanium shield, with an estimated total mass of 52 g and volume of 15 cm3. The monitor is intended to provide real-time dosimetry and identification of energetic charged particles in fluxes of up to 108 cm−2 s−1 (omnidirectional). Achieving this capability with such a small instrument could open new prospects for radiation detection in space.
Akerib DS, Araujo HM, Bai X, et al., 2014, First results from the LUX dark matter experiment at the Sanford Underground Research Facility, Physical Review Letters, Vol: 112, ISSN: 1079-7114
he 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 cm2 at a WIMP mass of 33 GeV/c2. We find that the LUX data are in disagreement with low-mass WIMP signal interpretations of the results from several recent direct detection experiments.
Akerib DS, Araújo HM, Bai X, et al., 2014, Direct search for dark matter with two-phase xenon detectors: Current status of LUX and plans for LZ, Pages: 51-58, ISSN: 1122-5157
The search for dark matter reaches back generations and remains one of the most compelling endeavors in the hunt for physics beyond the Standard Model. Experiments attempting to directly detect WIMP dark matter have made re-markable progress in increasing sensitivity to elastic scattering of WIMPs on nuclei. The LUX experiment is a 370-kg, two-phase, xenon TPC currently running at SURF, 4850 feet below Lead, SD. LUX recently completed its first science run and was sensitive to spin independent WIMP scattering at cross sections below 10-45 cm2 for WIMP masses of approximately 20 to 80 GeV. Preparations for the final science run of LUX are currently underway, with final results expected in 2015. We will present results from and current status of the LUX experiment, as well as plans for a follow-on, multi-ton-scale xenon experiment at SURF.
Guerrini N, Turchetta R, Griffin D, et al., 2013, Design and characterisation of a highly miniaturised radiation monitor HMRM, 6th International Workshop on Semiconductor Pixel Detectors for Particles and Imaging (PIXEL), Publisher: ELSEVIER SCIENCE BV, Pages: 154-159, ISSN: 0168-9002
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- Citations: 6
Reichhart L, Lindote A, Akimov DY, et al., 2013, Measurement and simulation of the muon-induced neutron yield in lead, ASTROPARTICLE PHYSICS, Vol: 47, Pages: 67-76, ISSN: 0927-6505
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- Citations: 32
Chepel V, Araujo H, 2013, Liquid noble gas detectors for low energy particle physics, Journal of Instrumentation, Vol: 8, ISSN: 1748-0221
We review the current status of liquid noble gas radiation detectors with energy threshold in the keV range, which are of interest for direct dark matter searches, measurement of coherent neutrino scattering and other low energy particle physics experiments. Emphasis is given to the operation principles and the most important instrumentation aspects of these detectors, principally of those operated in the double-phase mode. Recent technological advances and relevant developments in photon detection and charge readout are discussed in the context of their applicability to those experiments.
Reichhart L, Lindote A, Akimov DY, et al., 2013, A measurement of the muon-induced neutron yield in lead at a depth of 2850 m water equivalent, 4th International Workshop on Low Radioactivity Techniques (LRT), Publisher: AMER INST PHYSICS, Pages: 219-222, ISSN: 0094-243X
Solovov VN, Belov VA, Akimov DY, et al., 2012, Position Reconstruction in a Dual Phase Xenon Scintillation Detector, IEEE Transactions on Nuclear Science, Vol: 59, Pages: 3286-3293, ISSN: 1558-1578
We studied the application of statistical reconstruction algorithms, namely maximum likelihood and least squares methods, to the problem of event reconstruction in a dual phase liquid xenon detector. An iterative method was developed for in-situ reconstruction of the PMT light response functions from calibration data taken with an uncollimated γ -ray source. Using the techniques described, the performance of the ZEPLIN-III dark matter detector was studied for 122 keV γ-rays. For the inner part of the detector (R <; 100 mm) , spatial resolutions of 13 mm and 1.6 mm FWHM were measured in the horizontal plane for primary and secondary scintillation, respectively. An energy resolution of 8.1% FWHM was achieved at that energy. The possibility of using this technique for improving performance and reducing cost of scintillation cameras for medical applications is currently under study.
Reichhart L, Akimov DY, Araujo HM, et al., 2012, Quenching factor for low-energy nuclear recoils in a plastic scintillator, Physical Review C, Vol: 85, ISSN: 1089-490X
Plastic scintillators are widely used in industry, medicine, and scientific research, including nuclear and particle physics. Although one of their most common applications is in neutron detection, experimental data on their response to low-energy nuclear recoils are scarce. Here, the relative scintillation efficiency for neutron-induced nuclear recoils in a polystyrene-based plastic scintillator (UPS-923A) is presented, exploring recoil energies between 125 and 850 keV. Monte Carlo simulations, incorporating light collection efficiency and energy resolution effects, are used to generate neutron scattering spectra which are matched to observed distributions of scintillation signals to parameterize the energy-dependent quenching factor. At energies above 300 keV the dependence is reasonably described using the semiempirical formulation of Birks and a kB factor of (0.014±0.002) g MeV−1 cm−2 has been determined. Below that energy, the measured quenching factor falls more steeply than predicted by the Birks formalism.
Majewski P, Solovov VN, Akimov DY, et al., 2012, Performance data from the ZEPLIN-III second science run, Journal of Instrumentation, Vol: 7, ISSN: 1748-0221
ZEPLIN-III is a two-phase xenon direct dark matter experiment located at the Boulby Mine (U.K.). After its first science run in 2008 it was upgraded with: an array of low background photomultipliers, a new anti-coincidence detector system with plastic scintillator and an improved calibration system. After 319 days of data taking the second science run ended in May 2011. In this paper we describe the instrument performance with emphasis on the position and energy reconstruction algorithm and summarise the final science results.
Akimov DY, Araújo HM, Barnes EJ, et al., 2012, WIMP-nucleon cross-section results from the second science run of ZEPLIN-III, Physics Letters B, Vol: 709, Pages: 14-20, ISSN: 0370-2693
Araujo HM, Akimov DY, Barnes EJ, et al., 2012, Radioactivity backgrounds in ZEPLIN-III, ASTROPARTICLE PHYSICS, Vol: 35, Pages: 495-502, ISSN: 0927-6505
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- Citations: 22
Araujo H, 2012, Results From the Second Science Run of ZEPLIN-III, 19th Particles and Nuclei International Conference (PANIC), Publisher: AMER INST PHYSICS, Pages: 506-508, ISSN: 0094-243X
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- Citations: 1
Santos E, Edwards B, Chepel V, et al., 2011, Single electron emission in two-phase xenon with application to the detection of coherent neutrino-nucleus scattering, The Journal of High Energy Physics, Vol: 2011, Pages: 1-21, ISSN: 1029-8479
We present an experimental study of single electron emission in ZEPLIN-III, a two-phase xenon experiment built to search for dark matter WIMPs, and discuss appli-cations enabled by the excellent signal-to-noise ratio achieved in detecting this signature. Firstly, we demonstrate a practical method for precise measurement of the free electron lifetime in liquid xenon during normal operation of these detectors. Then, using a realistic detector response model and backgrounds, we assess the feasibility of deploying such an instrument for measuring coherent neutrino-nucleus elastic scattering using the ionisation channel in the few-electron regime. We conclude that it should be possible to measure this elusive neutrino signature above an ionisation threshold of ~3 electrons both at a stopped pion source and at a nuclear reactor. Detectable signal rates are larger in the reactor case, but the triggered measurement and harder recoil energy spectrum afforded by the accelerator source enable lower overall background and fiducialisation of the active volume.
Horn M, Belov VA, Akimov DY, et al., 2011, Nuclear recoil scintillation and ionisation yields in liquid xenon from ZEPLIN-III data, PHYSICS LETTERS B, Vol: 705, Pages: 471-476, ISSN: 0370-2693
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- Citations: 44
Neves F, Akimov DY, Araujo HM, et al., 2011, ZE3RA: the ZEPLIN-III Reduction and Analysis package, Journal of Instrumentation, Vol: 6, ISSN: 1748-0221
ZE3RA is the software package responsible for processing the raw data from the ZEPLIN-III dark matter experiment and its reduction into a set of parameters used in all subsequent analyses. The detector is a liquid xenon time projection chamber with scintillation and electroluminescence signals read out by an array of 31 photomultipliers. The dual range 62-channel data stream is optimised for the detection of scintillation pulses down to a single photoelectron and of ionisation signals as small as those produced by single electrons. We discuss in particular several strategies related to data filtering, pulse finding and pulse clustering which are tuned using calibration data to recover the best electron/nuclear recoil discrimination near the detection threshold, where most dark matter elastic scattering signatures are expected. The software was designed assuming only minimal knowledge of the physics underlying the detection principle, allowing an unbiased analysis of the experimental results and easy extension to other detectors with similar requirements.
Ghag C, Akimov DY, Araujo HM, et al., 2011, Performance of the veto detector incorporated into the ZEPLIN-III experiment, Astroparticle Physics, Vol: 35, Pages: 76-86, ISSN: 1873-2852
The ZEPLIN-III experiment is operating in its second phase at the Boulby Underground Laboratory in search of dark matter WIMPs. The major upgrades to the instrument over its first science run include lower background photomultiplier tubes and installation of a plastic scintillator veto system. Performance results from the veto detector using calibration and science data in its first six months of operation in coincidence with ZEPLIN-III are presented. With fully automated operation and calibration, the veto system has maintained high stability and achieves near unity live time relative to ZEPLIN-III. Calibrations with a neutron source demonstrate a rejection of 60% of neutron-induced nuclear recoils in ZEPLIN-III that might otherwise be misidentified as WIMPs. This tagging efficiency reduces the expected untagged nuclear recoil background from neutrons during science data taking to a very low rate of ≃0.2 events per year in the WIMP acceptance region. Additionally, the veto detector provides rejection of 28% of γ-ray induced background events, allowing the sampling of the dominant source of background in ZEPLIN-III – multiple scatter γ-rays with rare topologies. Since WIMPs will not be tagged by the veto detector, and tags due to γ-rays and neutrons are separable, this population of multiple scatter events may be characterised without biasing the analysis of candidate WIMP signals in the data.
Canizares P, Chmeissani M, Conchillo A, et al., 2011, The LISA Pathfinder DMU and Radiation Monitor, CLASSICAL AND QUANTUM GRAVITY, Vol: 28, ISSN: 0264-9381
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- Citations: 18
Grimani C, Araujo HM, Fabi M, et al., 2011, Galactic cosmic-ray energy spectra and expected solar events at the time of future space missions, CLASSICAL AND QUANTUM GRAVITY, Vol: 28, ISSN: 0264-9381
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- Citations: 6
Malling DC, Chapman JJ, Faham CH, et al., 2011, After LUX: The LZ program
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.
Araujo H, Canizares P, Chmeissani M, et al., 2011, Milli-Hertz Gravitational Waves: <i>LISA</i> and <i>LISA PathFinder</i>, Spanish Relativity Meeting (ERE 2010) on Gravity as a Crossroad in Physics, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
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- Citations: 3
Solovov VN, Belov VA, Akimov DY, et al., 2011, Position Reconstruction in a Dual Phase Xenon Scintillation Detector, IEEE Nuclear Science Symposium/Medical Imaging Conference (NSS/MIC)/18th International Workshop on Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors, Publisher: IEEE, Pages: 1226-1233, ISSN: 1095-7863
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- Citations: 1
Akimov DY, Araujo HM, Barnes EJ, et al., 2010, Limits on inelastic dark matter from ZEPLIN-III, Physics Letters B, Vol: 692, Pages: 180-183, ISSN: 0370-2693
We present limits on the WIMP–nucleon cross section for inelastic dark matter from a reanalysis of the2008 run of ZEPLIN-III. Cuts, notably on scintillation pulse shape and scintillation-to-ionisation ratio, givea net exposure of 63 kg day in the range 20–80 keV nuclear recoil energy, in which 6 events are observed.Upper limits on signal rate are derived from the maximum empty patch in the data. Under standard haloassumptions a small region of parameter space consistent, at 99% CL, with causing the 1.17 ton yr DAMAmodulation signal is allowed at 90% CL: it is in the mass range 45–60 GeVc−2 with a minimum CLof 87%, again derived from the maximum patch. This is the tightest constraint yet presented using xenon,a target nucleus whose similarity to iodine mitigiates systematic error from the assumed halo.
Akimov DY, Araujo HM, Barnes EJ, et al., 2010, The ZEPLIN-III anti-coincidence veto detector, Astroparticle Physics, Vol: 34, Pages: 151-163, ISSN: 1873-2852
The design, optimisation and construction of an anti-coincidence veto detector to complement the ZEPLIN-III direct dark matter search instrument is described. One tonne of plastic scintillator is arranged into 52 bars individually read out by photomultipliers and coupled to a gadolinium-loaded passive polypropylene shield. Particular attention has been paid to radiological content. The overall aim has been to achieve a veto detector of low threshold and high efficiency without the creation of additional background in ZEPLIN-III, all at a reasonable cost. Extensive experimental measurements of the components have been made, including radioactivity levels and performance characteristics. These have been used to inform a complete end-to-end Monte Carlo simulation that has then been used to calculate the expected performance of the new instrument, both operating alone and as an anti-coincidence detector for ZEPLIN-III. The veto device will be capable of rejecting over 65% of coincident nuclear recoil events from neutron background in the energy range of interest in ZEPLIN-III. This will reduce the background in ZEPLIN-III from ≃0.4 to ≃0.14 events per year in the WIMP acceptance region, a significant factor in the event of a non-zero observation. Furthermore, in addition to providing valuable diagnostic capabilities, the veto is capable of tagging over 15% for γ-ray rejection, all whilst contributing no significant additional background. In conjunction with the replacement of the internal ZEPLIN-III photomultiplier array, the new veto is expected to improve significantly the sensitivity of the ZEPLIN-III instrument to dark matter, allowing spin-independent WIMP-nucleon cross sections below 10−8 pb to be probed.
Grimani C, Araujo HM, Fabi M, et al., 2010, Short-term forecasting of solar energetic ions on board LISA, 8th Edoardo Amaldi Conference on Gravitational Waves, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
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- Citations: 4
Neves F, Chepel V, Akimov DY, et al., 2009, Calibration of photomultiplier arrays, Astroparticle Physics, Vol: 33, Pages: 13-18, ISSN: 1873-2852
A method is described that allows calibration and assessment of the linearity of response of an array of photomultiplier tubes. The method does not require knowledge of the photomultiplier single photoelectron response model and uses science data directly, thus eliminating the need for dedicated data sets. In this manner all photomultiplier working conditions (e.g. temperature, external fields, etc.) are exactly matched between calibration and science acquisitions. This is of particular importance in low background experiments such as ZEPLIN-III, where methods involving the use of external light sources for calibration are severely constrained.
Lebedenko VN, Araujo HM, Barnes EJ, et al., 2009, Limits on the Spin-Dependent WIMP-Nucleon Cross Sections from the First Science Run of the ZEPLIN-III Experiment, PHYSICAL REVIEW LETTERS, Vol: 103, ISSN: 0031-9007
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- Citations: 48
Lebedenko VN, Araujo HM, Barnes EJ, et al., 2009, Results from the first science run of the ZEPLIN-III dark matter search experiment, Physical Review D- particles, fields, gravitation, and cosmology, Vol: 80, ISSN: 1550-7998
The ZEPLIN-III experiment in the Palmer Underground Laboratory at Boulby uses a 12 kg two-phasexenon time-projection chamber to search for the weakly interacting massive particles (WIMPs) that mayaccount for the dark matter of our Galaxy. The detector measures both scintillation and ionizationproduced by radiation interacting in the liquid to differentiate between the nuclear recoils expected fromWIMPs and the electron-recoil background signals down to 10 keV nuclear-recoil energy. An analysisof 847 kg days of data acquired between February 27, 2008, and May 20, 2008, has excluded a WIMPnucleonelastic scattering spin-independent cross section above 8:1 10 8 pb at 60 GeVc 2 with a 90%confidence limit. It has also demonstrated that the two-phase xenon technique is capable of betterdiscrimination between electron and nuclear recoils at low-energy than previously achieved by otherxenon-based experiments.
Araujo H, 2009, Performance results from the first science run of ZEPLIN-III, 8th International Conference on Position Sensitive Detectors, Publisher: ELSEVIER, Pages: 41-44, ISSN: 0168-9002
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- Citations: 1
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