416 results found
Armano M, Audley H, Auger G, et al., 2015, A Strategy to Characterize the LISA-Pathfinder Cold Gas Thruster System, 10th International LISA Symposium, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Horn M, Akerib DS, Araujo HM, et al., 2014, Results from the LUX dark matter experiment, 15th Symposium on Radiation Measurements and Applications 2014 (SORMA XV), Publisher: Elsevier, Pages: 504-507, ISSN: 0168-9002
The LUX (Large Underground Xenon) experiment aims at the direct detection of dark matter particles via their collisions with xenon nuclei. The 370 kg two-phase liquid xenon time projection chamber measures simultaneously the scintillation and ionization from interactions in the target. The ratio of these two signals provides very good discrimination between potential nuclear recoil and electronic recoil signals to search for WIMP-nucleon scattering. The LUX detector operates at the Sanford Underground Research Facility (Lead, South Dakota, USA) since February 2013. First results were presented in late 2013 setting the world׳s most stringent limits on WIMP-nucleon scattering cross-sections over a wide range of WIMP masses. A 300 day run beginning in 2014 will further improve the sensitivity and new calibration techniques will reduce systematics for the WIMP signal search.
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.
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
Amaro-Seoane P, Aoudia S, Babak S, et al., 2013, eLISA/NGO: astrophysics and cosmology in the gravitational-wave millihertz regime, Gravitational Wave Notes, Vol: 6, Pages: 1-110, ISSN: 1868-1921
This document introduces the exciting and fundamentally new science and astronomy that the European New Gravitational Wave Observatory (NGO) mission (derived from the previous LISA proposal) will deliver. The mission (which we will refer to by its informal name ``eLISA'') will survey for the first time the low-frequency gravitational wave band (about 0:1 mHz to 1 Hz), with sufficient sensitivity to detect interesting individual astrophysical sources out to z = 15. The measurements described here will address the basic scientific goals that have been captured in ESA's ``New Gravitational Wave Observatory Science Requirements Document''; they are presented here so that the wider scientific community can have access to them. The eLISA mission will discover and study a variety of cosmic events and systems with high sensitivity: coalescences of massive black holes binaries, brought together by galaxy mergers; mergers of earlier, less-massive black holes during the epoch of hierarchical galaxy and black-hole growth; stellar-mass black holes and compact stars in orbits just skimming the horizons of massive black holes in galactic nuclei of the present era; extremely compact white dwarf binaries in our Galaxy, a rich source of information about binary evolution and about future Type Ia supernovae; and possibly most interesting of all, the uncertain and unpredicted sources, for example relics of inflation and of the symmetry-breaking epoch directly after the Big Bang. eLISA's measurements will allow detailed studies of these signals with high signal-to-noise ratio, addressing most of the key scientific questions raised by ESA's Cosmic Vision programme in the areas of astrophysics and cosmology. They will also provide stringent tests of general relativity in the strong-field dynamical regime, which cannot be probed in any other way. This document not only describes the science but also gives an overview on the mission design and orbits. LISA's heritage in the eLISA design wil
Nofrarias M, Antonucci F, Armano M, et al., 2013, State Space Modelling and Data Analysis Exercises in LISA Pathfinder, 9th LISA Symposium, Publisher: ASTRONOMICAL SOC PACIFIC, Pages: 161-+
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
McNamara P, Antonucci F, Armano M, et al., 2013, The LISA Pathfinder Mission, 9th LISA Symposium, Publisher: ASTRONOMICAL SOC PACIFIC, Pages: 5-+
Sumner TJ, 2013, Science with LISA Pathfinder, 9th LISA Symposium, Publisher: ASTRONOMICAL SOC PACIFIC, Pages: 129-139, ISSN: 1050-3390
Sumner TJ, 2012, First science results from the zeplin-III directdark matter search, Pages: 882-884
Edinburgh University, Imperial College London, ITEP, LIP-Coimbra, STFC-RAL ZEPLIN-III is a 12 kg two-phase xenon time projection chamber searching for weakly interacting massive particles (WIMPs) accounting for dark matter in our Galaxy. Scintillation and ionisation in the liquid differentiate between nuclear and electron recoils above 10 keVnr. 847 kgdays data acquired between Feb 27th and May 20th 2008 has excluded a coherent WIMP-nucleon scattering cross-section above 8.1x 10-8pb at 60 GHeVc-2 Copyright © 2012 by World Scientific Publishing Co. Pte. Ltd.
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.
Amaro-Seoane P, Aoudia S, Babak S, et al., 2012, Low-frequency gravitational-wave science with eLISA/NGO, Classical and Quantum Gravity, Vol: 29, ISSN: 1361-6382
We review the expected science performance of the New Gravitational-WaveObservatory (NGO, a.k.a. eLISA), a mission under study by the European SpaceAgency for launch in the early 2020s. eLISA will survey the low-frequencygravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizinga broad variety of systems and events throughout the Universe, including thecoalescences of massive black holes brought together by galaxy mergers; theinspirals of stellar-mass black holes and compact stars into central galacticblack holes; several millions of ultra-compact binaries, both detached and masstransferring, in the Galaxy; and possibly unforeseen sources such as the relicgravitational-wave radiation from the early Universe. eLISA’s high signal-tonoisemeasurements will provide new insight into the structure and history ofthe Universe, and they will test general relativity in its strong-field dynamicalregime.
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
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
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.
Audley H, Danzmann K, Marin AG, et al., 2011, The LISA Pathfinder interferometry-hardware and system testing, CLASSICAL AND QUANTUM GRAVITY, Vol: 28, ISSN: 0264-9381
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
Antonucci F, Armano M, Audley H, et al., 2011, From laboratory experiments to LISA Pathfinder: achieving LISA geodesic motion, Classical and Quantum Gravity, Vol: 28, ISSN: 1361-6382
This paper presents a quantitative assessment of the performance of the upcoming LISA Pathfinder geodesic explorer mission. The findings are based on the results of extensive ground testing and simulation campaigns using flight hardware, flight control and operations algorithms. The results show that, for the central experiment of measuring the stray differential acceleration between the LISA test masses, LISA Pathfinder will be able to verify the overall acceleration noise to within a factor 2 of the LISA requirement at 1 mHz and within a factor 6 at 0.1 mHz. We also discuss the key elements of the physical model of disturbances, coming from LISA Pathfinder and ground measurement that will guarantee the LISA performance.
Summer TJ, 2011, Direct dark matter searches - recent highlights, International Nuclear Physics Conference (INPC), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
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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