First limits on WIMP nuclear recoil signals in ZEPLIN-II: A two-phase xenon detector for dark matter detection
By G. J. Alner, H. Araujo, A. Bewick, C. Bungau, B. Camanzi, M. Carson, R. Cashmore, H. Chagani, V. Chepel, D. Cline and 52 more. 2007
145 citations recorded by the source corpus.
Abstract Results are presented from the first underground data run of ZEPLIN-II, a 31 kg two-phase xenon detector developed to observe nuclear recoils from hypothetical weakly interacting massive dark matter particles. Discrimination between nuclear recoils and background electron recoils is afforded by recording both the scintillation and ionisation signals generated within the liquid xenon, with the ratio of these signals being different for the two classes of event. This ratio is calibrated for different incident species using an AmBe neutron source and 60 Co γ-ray sources. From our first 31 live days of running ZEPLIN-II, the total exposure following the application of fiducial and stability cuts was 225 kg × days. A background population of radon progeny events was observed in this run, arising from radon emission in the gas purification getters, due to radon daughter ion decays on the surfaces of the walls of the chamber. An acceptance window, defined by the neutron calibration data, of 50% nuclear recoil acceptance between 5 keV ee and 20 keV ee , had an observed count of 29 events, with a summed expectation of 28.6 ± 4.3 γ-ray and radon progeny induced background events. These figures provide a 90% c.l. upper limit to the number of nuclear recoils of 10.4 events in this acceptance window, which converts to a WIMP–nucleon spin-independent cross-section with a minimum of 6.6 × 10 −7 pb following the inclusion of an energy-dependent, calibrated, efficiency. A second run is currently underway in which the radon progeny will be eliminated, thereby removing the background population, with a projected sensitivity of 2 × 10 −7 pb for similar exposures as the first run.
Subfields: Atomic and Molecular Physics, and Optics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/20a680ff154f61d2b19f075e905eb4159b4242ea
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Citations in the corpus
- The impact of priors and observables on parameter inferences in the constrained MSSM (2008, background): “The current strongest experimental 90% CL limits from CDMS [50], XENON-10 [51] and ZEPLIN-II [52] have also been marked for comparison (athough they have not been imposed as constraints in the analysis).”
- Dark matter direct detection with non-Maxwellian velocity structure (2009, methodology): “Recent studies [27, 25, 41, 42] have shown that iDM remains a viable explanation of the DAMA data, consistent with recent results from CDMS [43], XENON10 [44], KIMS [45], ZEPLIN II [46], ZEPLIN III [47] and CRESST [48].”
- Liquid noble gas detectors for low energy particle physics (2012, methodology): “ZEPLIN-III concluded the liquid xenon program at Boulby, with – 70 – science runs in 2008 [376] and, following an upgrade phase, in 2010/11 [56]; its design featured 31 2-inch PMTs immersed in the liquid, viewing a thin disc geometry of 12 kg of liquid xenon under high electric field [50].”