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Search Results: 1 - 10 of 673028 matches for " A. S. Kobyakin "
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Experimental study of ionization yield of liquid xenon for electron recoils in the energy range 2.8 - 80 keV
D. Yu. Akimov,V. V. Afanasyev,I. S. Alexandrov,V. A. Belov,A. I. Bolozdynya,A. A. Burenkov,Yu. V. Efremenko,D. A. Egorov,A. V. Etenko,M. A. Gulin,S. V. Ivakhin,V. A. Kaplin,A. K. Karelin,A. V. Khromov,M. A. Kirsanov,S. G. Klimanov,A. S. Kobyakin,A. M. Konovalov,A. G. Kovalenko,A. V. Kuchenkov,A. V. Kumpan,Yu. A. Melikyan,R. I. Nikolaev,D. G. Rudik,V. V. Sosnovtsev,V. N. Stekhanov
Physics , 2014, DOI: 10.1088/1748-0221/9/11/P11014
Abstract: We present the results of the first experimental study of ionization yield of electron recoils with energies below 100 keV produced in liquid xenon by the isotopes: 37Ar, 83mKr, 241Am, 129Xe, 131Xe. It is confirmed by a direct measurement with 37Ar isotope (2.82 keV) that the ionization yield is growing up with the energy decrease in the energy range below ~ 10 keV accordingly to the NEST predictions. Decay time of scintillation at 2.82 keV is measured to be 25 +/- 3 ns at the electric field of 3.75 kV/cm.
DANSSino: a pilot version of the DANSS neutrino detector
I. Alekseev,V. Belov,V. Brudanin,M. Danilov,V. Egorov,D. Filosofov,M. Fomina,Z. Hons,A. Kobyakin,D. Medvedev,R. Mizuk,E. Novikov,A. Olshevsky,S. Rozov,N. Rumyantseva,V. Rusinov,A. Salamatin,Ye. Shevchik,M. Shirchenko,Yu. Shitov,A. Starostin,D. Svirida,E. Tarkovsky,I. Tikhomirov,E. Yakushev,I. Zhitnikov,D. Zinatulina
Physics , 2013, DOI: 10.1134/S1547477114040050
Abstract: DANSSino is a reduced pilot version of a solid-state detector of reactor antineutrinos (to be created within the DANSS project and installed under the industrial 3 GW(th) reactor of the Kalinin Nuclear Power Plant -- KNPP). Numerous tests performed at a distance of 11 m from the reactor core demonstrate operability of the chosen design and reveal the main sources of the background. In spite of its small size (20x20x100 ccm), the pilot detector turned out to be quite sensitive to reactor antineutrinos, detecting about 70 IBD events per day with the signal-to-background ratio about unity.
ZE3RA: The ZEPLIN-III Reduction and Analysis Package
F. Neves,D. Yu. Akimov,H. M. Araújo,E. J. Barnes,V. A. Belov,A. A. Burenkov,V. Chepel,A. Currie,L. DeViveiros,B. Edwards,C. Ghag,A. Hollingsworth,M. Horn,G. E. Kalmus,A. S. Kobyakin,A. G. Kovalenko,V. N. Lebedenko,A. Lindote,M. I. Lopes,R. Lüscher,P. Majewski,A. St J. Murphy,S. M. Paling,J. Pinto da Cunha,R. Preece,J. J. Quenby,L. Reichhart,S. Rodrigues,P. R. Scovell,C. Silva,V. N. Solovov,N. J. T. Smith,P. F. Smith,V. N. Stekhanov,T. J. Sumner,C. Thorne,R. J. Walker
Physics , 2011, DOI: 10.1088/1748-0221/6/11/P11004
Abstract: 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 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.
Measurement and simulation of the muon-induced neutron yield in lead
L. Reichhart,A. Lindote,D. Yu. Akimov,H. M. Araujo,E. J. Barnes,V. A. Belov,A. Bewick,A. A. Burenkov,V. Chepel,A. Currie,L. DeViveiros,B. Edwards,V. Francis,C. Ghag,A. Hollingsworth,M. Horn,G. E. Kalmus,A. S. Kobyakin,A. G. Kovalenko,V. A. Kudryavtsev,V. N. Lebedenko,M. I. Lopes,R. Luscher,P. Majewski,A. St J. Murphy,F. Neves,S. M. Paling,J. Pinto da Cunha,R. Preece,J. J. Quenby,P. R. Scovell,C. Silva,V. N. Solovov,N. J. T. Smith,P. F. Smith,V. N. Stekhanov,T. J. Sumner,C. Thorne,R. J. Walker
Physics , 2013, DOI: 10.1016/j.astropartphys.2013.06.002
Abstract: A measurement is presented of the neutron production rate in lead by high energy cosmic-ray muons at a depth of 2850 m water equivalent (w.e.) and a mean muon energy of 260 GeV. The measurement exploits the delayed coincidences between muons and the radiative capture of induced neutrons in a highly segmented tonne scale plastic scintillator detector. Detailed Monte Carlo simulations reproduce well the measured capture times and multiplicities and, within the dynamic range of the instrumentation, the spectrum of energy deposits. By comparing measurements with simulations of neutron capture rates a neutron yield in lead of (5.78^{+0.21}_{-0.28}) x 10^{-3} neutrons/muon/(g/cm^{2}) has been obtained. Absolute agreement between simulation and data is of order 25%. Consequences for deep underground rare event searches are discussed.
WIMP-nucleon cross-section results from the second science run of ZEPLIN-III
D. Yu. Akimov,H. M. Araujo,E. J. Barnes,V. A. Belov,A. Bewick,A. A. Burenkov,V. Chepel,A. Currie,L. DeViveiros,B. Edwards,C. Ghag,A. Hollingsworth,M. Horn,W. G. Jones,G. E. Kalmus,A. S. Kobyakin,A. G. Kovalenko,V. N. Lebedenko,A. Lindote,M. I. Lopes,R. Luscher,P. Majewski,A. StJ. Murphy,F. Neves,S. M. Paling,J. Pinto da Cunha,R. Preece,J. J. Quenby,L. Reichhart,P. R. Scovell,C. Silva,V. N. Solovov,N. J. T. Smith,V. N. Stekhanov,T. J. Sumner,C. Thorne,R. J. Walker
Physics , 2011, DOI: 10.1016/j.physletb.2012.01.064
Abstract: We report experimental upper limits on WIMP-nucleon elastic scattering cross sections from the second science run of ZEPLIN-III at the Boulby Underground Laboratory. A raw fiducial exposure of 1,344 kg.days was accrued over 319 days of continuous operation between June 2010 and May 2011. A total of eight events was observed in the signal acceptance region in the nuclear recoil energy range 7-29 keV, which is compatible with background expectations. This allows the exclusion of the scalar cross-section above 4.8E-8 pb near 50 GeV/c^2 WIMP mass with 90% confidence. Combined with data from the first run, this result improves to 3.9E-8 pb. The corresponding WIMP-neutron spin-dependent cross-section limit is 8.0E-3 pb. The ZEPLIN programme reaches thus its conclusion at Boulby, having deployed and exploited successfully three liquid xenon experiments of increasing reach.
Radioactivity Backgrounds in ZEPLIN-III
H. M. Araujo,D. Yu. Akimov,E. J. Barnes,V. A. Belov,A. Bewick,A. A. Burenkov,V. Chepel. A. Currie,L. DeViveiros,B. Edwards,C. Ghag,A. Hollingsworth,M. Horn,G. E. Kalmus,A. S. Kobyakin,A. G. Kovalenko,V. N. Lebedenko,A. Lindote,M. I. Lopes,R. Luscher,P. Majewski,A. StJ. Murphy. F. Neves,S. M. Paling,J. Pinto da Cunha,R. Preece,J. J. Quenby,L. Reichhart,P. R. Scovell,C. Silva,V. N. Solovov,N. J. T. Smith,P. F. Smith,V. N. Stekhanov,T. J. Sumner,C. Thorne,R. J. Walker
Physics , 2011, DOI: 10.1016/j.astropartphys.2011.11.001
Abstract: We examine electron and nuclear recoil backgrounds from radioactivity in the ZEPLIN-III dark matter experiment at Boulby. The rate of low-energy electron recoils in the liquid xenon WIMP target is 0.75$\pm$0.05 events/kg/day/keV, which represents a 20-fold improvement over the rate observed during the first science run. Energy and spatial distributions agree with those predicted by component-level Monte Carlo simulations propagating the effects of the radiological contamination measured for materials employed in the experiment. Neutron elastic scattering is predicted to yield 3.05$\pm$0.5 nuclear recoils with energy 5-50 keV per year, which translates to an expectation of 0.4 events in a 1-year dataset in anti-coincidence with the veto detector for realistic signal acceptance. Less obvious background sources are discussed, especially in the context of future experiments. These include contamination of scintillation pulses with Cherenkov light from Compton electrons and from $\beta$ activity internal to photomultipliers, which can increase the size and lower the apparent time constant of the scintillation response. Another challenge is posed by multiple-scatter $\gamma$-rays with one or more vertices in regions that yield no ionisation. If the discrimination power achieved in the first run can be replicated, ZEPLIN-III should reach a sensitivity of $\sim 1 \times 10^{-8}$ pb$\cdot$year to the scalar WIMP-nucleon elastic cross-section, as originally conceived.
The ZEPLIN-III Anti-Coincidence Veto Detector
D. Yu. Akimov,H. M. Araujo,E. J. Barnes,V. A. Belov,A. A. Burenkov,V. Chepel,A. Currie,B. Edwards,V. Francis,C. Ghag,A. Hollingsworth,M. Horn,G. E. Kalmus,A. S. Kobyakin,A. G. Kovalenko,V. N. Lebedenko,A. Lindote,M. I. Lopes,R. Luscher,K. Lyons,P. Majewski,A. StJ. Murphy,F. Neves,S. M. Paling,J. Pinto da Cunha,R. Preece,J. J. Quenby,L. Reichhart,P. R. Scovell,V. N. Solovov,N. J. T. Smith,P. F. Smith,V. N. Stekhanov,T. J. Sumner,R. Taylor,C. Thorne,R. J. Walker
Physics , 2010, DOI: 10.1016/j.astropartphys.2010.06.010
Abstract: 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 gamma-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 1E-8 pb to be probed.
Nuclear recoil scintillation and ionisation yields in liquid xenon from ZEPLIN-III data
M. Horn,V. A. Belov,D. Yu. Akimov,H. M. Araújo,E. J. Barnes,A. A. Burenkov,V. Chepel,A. Currie,B. Edwards,C. Ghag,A. Hollingsworth,G. E. Kalmus,A. S. Kobyakin,A. G. Kovalenko,V. N. Lebedenko,A. Lindote,M. I. Lopes,R. Lüscher,P. Majewski,A. StJ. Murphy,F. Neves,S. M. Paling,J. Pinto da Cunha,R. Preece,J. J. Quenby,L. Reichhart,P. R. Scovell,C. Silva,V. N. Solovov,N. J. T. Smith,P. F. Smith,V. N. Stekhanov,T. J. Sumner,C. Thorne,L. de Viveiros,R. J. Walker
Physics , 2011, DOI: 10.1016/j.physletb.2011.10.038
Abstract: Scintillation and ionisation yields for nuclear recoils in liquid xenon above 10 keVnr (nuclear recoil energy) are deduced from data acquired using broadband Am-Be neutron sources. The nuclear recoil data from several exposures to two sources were compared to detailed simulations. Energy-dependent scintillation and ionisation yields giving acceptable fits to the data were derived. Efficiency and resolution effects are treated using a light collection Monte Carlo, measured photomultiplier response profiles and hardware trigger studies. A gradual fall in scintillation yield below ~40 keVnr is found, together with a rising ionisation yield; both are in good agreement with the latest independent measurements. The analysis method is applied to both the most recent ZEPLIN-III data, acquired with a significantly upgraded detector and a precision-calibrated Am-Be source, as well as to the earlier data from the first run in 2008. A new method for deriving the recoil scintillation yield, which includes sub-threshold S1 events, is also presented which confirms the main analysis.
Quenching Factor for Low Energy Nuclear Recoils in a Plastic Scintillator
L. Reichhart,D. Yu. Akimov,H. M. Araujo,E. J. Barnes,V. A. Belov,A. A. Burenkov,V. Chepel,A. Currie,L. DeViveiros,B. Edwards,V. Francis,C. Ghag,A. Hollingsworth,M. Horn,G. E. Kalmus,A. S. Kobyakin,A. G. Kovalenko,V. N. Lebedenko,A. Lindote,M. I. Lopes,R. Luscher,P. Majewski,A. St J. Murphy,F. Neves,S. M. Paling,J. Pinto da Cunha,R. Preece,J. J. Quenby,P. R. Scovell,C. Silva,V. N. Solovov,N. J. T. Smith,P. F. Smith,V. N. Stekhanov,T. J. Sumner,C. Thorne,R. J. Walker
Physics , 2011, DOI: 10.1103/PhysRevC.85.065801
Abstract: 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 keV 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 parameterise the energy-dependent quenching factor. At energies above 300 keV the dependence is reasonably described using the semi-empirical formulation of Birks and a kB factor of (0.014+/-0.002) g/MeVcm^2 has been determined. Below that energy the measured quenching factor falls more steeply than predicted by the Birks formalism.
Performance of the veto detector incorporated into the ZEPLIN-III experiment
C. Ghag,D. Yu. Akimov,H. M. Araújo,E. J. Barnes,V. A. Belov,A. A. Burenkov,V. Chepel,A. Currie,L. DeViveiros,B. Edwards,V. Francis,A. Hollingsworth,M. Horn,G. E. Kalmus,A. S. Kobyakin,A. G. Kovalenko,V. N. Lebedenko,A. Lindote,M. I. Lopes,R. Lüscher,K. Lyons,P. Majewski,A. St,J. Murphy,F. Neves,S. M. Paling,J. Pinto da Cunha,R. Preece,J. J. Quenby,L. Reichhart,P. R. Scovell,C. Silva,V. N. Solovov,N. J. T. Smith,P. F. Smith,V. N. Stekhanov,T. J. Sumner,C. Thorne,R. J. Walker
Physics , 2011, DOI: 10.1016/j.astropartphys.2011.06.006
Abstract: 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 gamma-ray induced background events, allowing the sampling of the dominant source of background in ZEPLIN-III - multiple scatter gamma-rays with rare topologies. Since WIMPs will not be tagged by the veto detector, and tags due to gamma-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.
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