Two depositional models to account for Holocene gravel-dominated beach ridges covered by dunes, occurring on the northern coast of Ireland, are considered in the light of infrared-stimulated ...luminescence ages of sand units within beach ridges, and
14C ages from organic horizons in dunes. A new chronostratigraphy obtained from prograded beach ridges with covering dunes at Murlough, north-east Ireland, supports a model of mesoscale alternating sediment decoupling (ASD) on the upper beach, rather than macroscale sequential sediment sourcing to account for prograded beach ridges and covering dunes. The ASD model specifies storm or fair-weather sand beach ridges forming at high-tide positions (on an annual basis at minimum), which acted as deflationary sources for landward foredune development. Only a limited number of such late-Holocene beach ridges survive in the observed prograded series. Beach ridges only survive when capped by storm-generated gravel beaches that are deposited on a mesoscale time spacing of 50–130 years. The morphodynamic shift from a dissipative beach face for dune formation to a reflective beach face for gravel capping appears to be controlled by the beach sand volume falling to a level where reflective conditions can prevail. Sediment volume entering the beach is thought to have fluctuated as a function of a forced regression associated with the falling sea level from the mid-Holocene highstand (ca. 6000 cal. yr BP) identified in north-east Ireland. The prograded beach ridges dated at ca. 3000 to 2000 cal. yr BP indicate that the Holocene highstand’s regressive phase may have lasted longer than previously specified.
The LUX-ZEPLIN (LZ) experiment is a dark matter detector centered on a dual-phase xenon time projection chamber. We report searches for new physics appearing through few-keV-scale electron recoils, ...using the experiment’s first exposure of 60 live days and a fiducial mass of 5.5 t. The data are found to be
consistent with a background-only hypothesis, and limits are set on models for new physics including solar axion electron coupling, solar neutrino magnetic moment and millicharge, and electron couplings to galactic axionlike particles and hidden photons. Similar limits are set on weakly interacting massive
particle (WIMP) dark matter producing signals through ionized atomic states from the Migdal effect.
The LUX-ZEPLIN experiment recently reported limits on WIMP-nucleus interactions from its initial science run, down to 9.2 x 10–48 cm2 for the spin-independent interaction of a 36 GeV/c2 WIMP at 90% ...confidence level. In this paper, we present a comprehensive analysis of the backgrounds important for this result and for other upcoming physics analyses, including neutrinoless double-beta decay searches and effective field theory interpretations of LUX-ZEPLIN data. We confirm that the in-situ determinations of bulk and fixed radioactive backgrounds are consistent with expectations from the ex-situ assays. The observed background rate after WIMP search criteria were applied was (6.3 ± 0.5) x 10–5 events /keVee/kg/day in the low-energy region, approximately 60 times lower than the equivalent rate reported by the LUX experiment.
Following the first science results of the LUX-ZEPLIN (LZ) experiment, a dual-phase xenon time projection chamber operating from the Sanford Underground Research Facility in Lead, South Dakota, USA, ...we report the initial limits on a model-independent nonrelativistic effective field theory describing the complete set of possible interactions of a weakly interacting massive particle (WIMP) with a nucleon. These results utilize the same 5.5 t fiducial mass and 60 live days of exposure collected for the LZ spin-independent and spin-dependent analyses while extending the upper limit of the energy region of interest by a factor of 7.5 to 270 keV. No significant excess in this high energy region is observed. Using a profile-likelihood ratio analysis, we report 90% confidence level exclusion limits on the coupling of each individual nonrelativistic WIMP-nucleon operator for both elastic and inelastic interactions in the isoscalar and isovector bases.
Published by the American Physical Society
2024
Searches for dark matter with liquid xenon time projection chamber experiments have traditionally focused on the region of the parameter space that is characteristic of weakly interacting massive ...particles, ranging from a few GeV/c2 to a few TeV/c2. Models of dark matter with a mass much heavier than this are well motivated by early production mechanisms different from the standard thermal freeze-out, but they have generally been less explored experimentally. In this work, we present a reanalysis of the first science run of the LZ experiment, with an exposure of 0.9 tonne x yr, to search for ultraheavy particle dark matter. The signal topology consists of multiple energy deposits in the active region of the detector forming a straight line, from which the velocity of the incoming particle can be reconstructed on an event-by-event basis. Zero events with this topology were observed after applying the data selection calibrated on a simulated sample of signal-like events. New experimental constraints are derived, which rule out previously unexplored regions of the dark matter parameter space of spin-independent interactions beyond a mass of 1017 GeV/c2.
The data acquisition system of the LZ dark matter detector: FADR Aalbers, J.; Al Musalhi, A.K.; Amarasinghe, C.S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
November 2024, 2024-11-00, Letnik:
1068
Journal Article
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The Data Acquisition System (DAQ) for the LUX-ZEPLIN (LZ) dark matter detector is described. The signals from 745 PMTs, distributed across three subsystems, are sampled with 100-MHz 32-channel ...digitizers (DDC-32s). A basic waveform analysis is carried out on the on-board Field Programmable Gate Arrays (FPGAs) to extract information about the observed scintillation and electroluminescence signals. This information is used to determine if the digitized waveforms should be preserved for offline analysis.
The system is designed around the Kintex-7 FPGA. In addition to digitizing the PMT signals and providing basic event selection in real time, the flexibility provided by the use of FPGAs allows us to monitor the performance of the detector and the DAQ in parallel to normal data acquisition.
The hardware and software/firmware of this FPGA-based Architecture for Data acquisition and Realtime monitoring (FADR) are discussed and performance measurements are described.
The aim of this study was to determine the risk factors for admission to hospital with stroke by means of a case-control study recruiting age- and sex-matched controls from the local community. Four ...hundred pairs of patients and controls were recruited. Of historical factors, preceding cerebrovascular disease contributed the greatest odds of stroke (odds ratio 9.8). Taking prescribed medicines (odds ratio 2.6), regular snoring (odds ratio 3.2), smoking (odds ratio 1.7) and some factors in the family history were also significant risk factors.
In a case-controlled study into the risk factors for admission to hospital with stroke, 400 subjects and 400 age and sex-matched controls were recruited. All bar two subjects were followed until ...death or 6 months. Previous stroke and regular snoring (p = 0.0013 and p < 0.0001 respectively) were the only two risk factors adversely to effect mortality. Transient ischaemic attack, ischaemic heart diseasehypertension, atrial fibrillation, diabetes mellitus did not significantly effect prognosis. An apparent beneficial effect of drinking alcohol and smoking became insignificant when the confounding influence of age was taken into account.
In this paper, we present the design, implementation, and evaluation of a custom-built wideband RF front-end for enabling dynamic spectrum access communications in software-defined radio platforms. ...The frontend is designed for wireless operation within the 50 MHz - 2.5 GHz frequency range, and is entirely software-controlled by the platform. Evaluation of the proposed design was conducted using the Universal Software Radio Peripheral (USRP) software defined radio platform and controlled via GNU Radio software. A prototype of the design was successfully demonstrated over a wide range of frequencies. Finally, several remaining design challenges are identified that would further enhance transmission performance.
This thesis evaluates the effectiveness of the Fleet Support community's management practices in meeting the dynamic changes in the complex fleet support arena, while increasing its value to the Navy ...in the future. The Fleet Support community's mission statement was used as a benchmark in the evaluation process. Data on billet base management, accession policies, education and the detailing process were evaluated against the mission statement to determine the extent to which these practices support it. The results of the study indicate that current practices provide limited support in meeting the Fleet Support community's mission statement.
