LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above
1.4
×
10
-
48
cm
2
for a WIMP mass of
40
GeV
/
c
2
and a
1000
days
...exposure. LZ achieves this sensitivity through a combination of a large
5.6
t
fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
We estimate the amount of 37Ar produced in natural xenon via cosmic-ray-induced spallation, an inevitable consequence of the transportation and storage of xenon on the Earth’s surface. We then ...calculate the resulting 37Ar concentration in a 10-tonne payload (similar to that of the LUX-ZEPLIN experiment) assuming a representative schedule of xenon purification, storage, and delivery to the underground facility. Using the spallation model by Silberberg and Tsao, the sea-level production rate of 37Ar in natural xenon is estimated to be 0.024 atoms/ kg/day . Assuming the xenon is successively purified to remove radioactive contaminants in 1-tonne batches at a rate of 1 tonne/month, the average 37Ar activity after 10 tons are purified and transported underground is 0.058 - 0.090 μBq/kg , depending on the degree of argon removal during above-ground purification. Such cosmogenic 37Ar will appear as a noticeable background in the early science data, while decaying with a 35-day half-life. This newly noticed production mechanism of 37Ar should be considered when planning for future liquid-xenon-based experiments.
The visible world is founded on the proton, the only composite building block of matter that is stable in nature. Consequently, understanding the formation of matter relies on explaining the dynamics ...and the properties of the proton's bound state. A fundamental property of the proton involves the response of the system to an external electromagnetic field. It is characterized by the electromagnetic polarizabilities
that describe how easily the charge and magnetization distributions inside the system are distorted by the electromagnetic field. Moreover, the generalized polarizabilities
map out the resulting deformation of the densities in a proton subject to an electromagnetic field. They disclose essential information about the underlying system dynamics and provide a key for decoding the proton structure in terms of the theory of the strong interaction that binds its elementary quark and gluon constituents. Of particular interest is a puzzle in the electric generalized polarizability of the proton that remains unresolved for two decades
. Here we report measurements of the proton's electromagnetic generalized polarizabilities at low four-momentum transfer squared. We show evidence of an anomaly to the behaviour of the proton's electric generalized polarizability that contradicts the predictions of nuclear theory and derive its signature in the spatial distribution of the induced polarization in the proton. The reported measurements suggest the presence of a new, not-yet-understood dynamical mechanism in the proton and present notable challenges to the nuclear theory.
LUX-ZEPLIN (LZ) is a next-generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. ...Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with weakly interacting massive particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6-tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above 1.4 × 10−48 cm2 for a 40 GeV/c2 mass WIMP. Additionally, a 5 σ discovery potential is projected, reaching cross sections below the exclusion limits of recent experiments. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of 2.3 × 10−43 cm2 (7.1 × 10−42 cm2) for a 40 GeV/c2 mass WIMP is expected. With underground installation well underway, LZ is on track for commissioning at SURF in 2020.
LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above 1.4 × 10-48 cm2 for a WIMP mass of 40 GeV/c 2 and a 1000 d ...exposure. LZ achieves this sensitivity through a combination of a large 5.6 t fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and be spoke detector systems to assay scintillator are presented.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
8.
The LUX-ZEPLIN (LZ) experiment Akimov, D.Yu; Angelides, N.; Araújo, H.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Letnik:
953, Številka:
C
Journal Article
Recenzirano
Odprti dostop
We describe the design and assembly of the LUX-ZEPLIN experiment, a direct detection search for cosmic WIMP dark matter particles. The centerpiece of the experiment is a large liquid xenon time ...projection chamber sensitive to low energy nuclear recoils. Rejection of backgrounds is enhanced by a Xe skin veto detector and by a liquid scintillator Outer Detector loaded with gadolinium for efficient neutron capture and tagging. LZ is located in the Davis Cavern at the 4850’ level of the Sanford Underground Research Facility in Lead, South Dakota, USA. We describe the major subsystems of the experiment and its key design features and requirements.
The purpose of this study was to describe the spectrum of radiologic and pathologic manifestations of calcific tendinitis involving bone.
We retrospectively reviewed 50 cases of calcific tendinitis ...involving underlying bone. Clinical data reviewed included patient age and sex and lesion location. Images reviewed included radiographs (n = 44), CT scans (n = 13), MRIs (n = 16), and bone scintigrams (n = 13). Radiologic examinations were evaluated for the presence of cortical erosion, periosteal reaction, and marrow extension. Pathology confirmation was available in 37 cases.
The average age of patients was 50 years (range, 16-82 years), with 29 female patients (58%). Calcific tendinitis with associated bone involvement was seen most commonly in the femur (40%) and the humerus (40%). Concretions were most commonly solid-appearing (50%). Cortical erosion was the most common manifestation of osseous involvement (78% of cases). Marrow involvement was shown in 18 (36%) of 50 cases. Marrow extension was most commonly seen in the lesser and greater tuberosities of the humerus, which accounted for 61% (11/18) of cases. Focal increased radionuclide uptake was seen in 13 (100%) of 13 cases.
Calcific tendinitis presenting with osseous destruction, marrow changes, and soft-tissue calcifications may be confused with neoplasm both radiologically and pathologically. Recognition of the atypical presentation of this common disease may prevent unnecessary biopsy.
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