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 non-relativistic 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 keVnr. 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 non-relativistic WIMP-nucleon operator for both elastic and inelastic interactions in the isoscalar and isovector bases.
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/\(c^2\) to a few TeV/\(c^2\). 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 re-analysis of the first science run (SR1) of the LZ experiment, with an exposure of \(0.9\) tonne\(\times\)year, 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 10\(^{17}\) GeV/\(c^2\).
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 5.5t. 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 axion-like 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.
Invasion and angiogenesis are two of the major hallmarks of glioblastoma growth. While tumor cells in angiogenic areas undergo hypoxic stress, invasive tumor cells are often found in less hypoxic ...areas and in close vicinity to brain vessels. This difference in microenvironment most likely influences the metabolic profile of these two different types of tumor cells. However, there is a lack of suitable in vivo models for malignant glioma to experimentally separate invasive and angiogenic tumor cells in order to analyze their metabolism. In the present study we used a human GBM xenograft model with EGFR amplification that grows invasive and independent of angiogenesis. This tumor undergoes an angiogenic switch upon overexpression of a dominant-negative EGFR mutant. Here, we show that the transcription factors Smad3, BHLHE40, CEB/P and STAT3 are central transcriptional regulators of the angiogenic switch in this model. By using the REMBRANDT database to assess the clinical relevance of our model, we found that genes upregulated in the angiogenic xenografts are also upregulated in patient GBMs compared to low grades, while the genes upregulated in the invasive tumors are upregulated in low-grade gliomas compared to GBMs. Within the xenograft model, we analyzed the metabolic differences between invasive and angiogenic tumor phenotypes. In vivo MRI spectroscopy showed an upregulation of lactate and glutamine in the angiogenic compared to invasive xenografts. The upregulation of glycolysis in angiogenic xenografts was confirmed by enzymehistochemistry of key enzymes, which in addition showed a substantial upregulation of pentose-phosphate pathway activity. Analysis of mitochondrial respiratory chain revealed reduction of complex I in angiogenic xenografts compared to invasive xenografts. Thus, the use of glycolysis for energy production within human GBMs is highly dependent on the specific microenvironment. The metabolic flexibility of GBM cells highlights the difficulty of targeting one specific metabolic pathway for therapy.
Background: There have been a number of reports of brain abscesses suggesting an odontogenic etiology. However, no efforts have been made to compare brain abscess isolates with isolates from the oral ...cavity using highly discriminative methods. We report a brain abscess caused by Streptococcus constellatus in an immunocompromised patient where oral infection (periodontitis) was suspected to be implicated.
Methods: The brain abscess and oral isolates were compared by means of one phenotypic and three genetic (restriction fragment length polymorphism RFLP, ribotyping, and random amplified polymorphic DNA RAPD) fingerprinting techniques.
Results: The phenotypic method and RFLP showed identical profiles between brain and periodontal isolates, while ribotyping and RAPD showed very close similarity, with only one band difference in one of the three ribotypes and in one of the three polymorphic RAPD.
Conclusions: Gene transfer by genetic recombinational events in the periodontal pocket might have been responsible for the emergence of a strain variant of S. constellatusthat had the potential to cause an abscess at a distant site (brain). The importance of odontogenic sources as potential foci of infection for brain abscesses is discussed. J Periodontol 2004;75:1720‐1723.
We estimate the amount of \(^{37}\)Ar 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 \(^{37}\)Ar 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 \(^{37}\)Ar 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 \(^{37}\)Ar activity after 10~tonnes are purified and transported underground is 0.058--0.090~\(\mu\)Bq/kg, depending on the degree of argon removal during above-ground purification. Such cosmogenic \(^{37}\)Ar 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 \(^{37}\)Ar should be considered when planning for future liquid xenon-based experiments.
The projected sensitivity of the LUX-ZEPLIN (LZ) experiment to two-neutrino and neutrinoless double beta decay of \(^{134}\)Xe is presented. LZ is a 10-tonne xenon time projection chamber optimized ...for the detection of dark matter particles, that is expected to start operating in 2021 at Sanford Underground Research Facility, USA. Its large mass of natural xenon provides an exceptional opportunity to search for the double beta decay of \(^{134}\)Xe, for which xenon detectors enriched in \(^{136}\)Xe are less effective. For the two-neutrino decay mode, LZ is predicted to exclude values of the half-life up to 1.7\(\times\)10\(^{24}\) years at 90% confidence level (CL), and has a three-sigma observation potential of 8.7\(\times\)10\(^{23}\) years, approaching the predictions of nuclear models. For the neutrinoless decay mode LZ, is projected to exclude values of the half-life up to 7.3\(\times\)10\(^{24}\) years at 90% CL.
LUX-ZEPLIN (LZ) is a dark matter detector expected to obtain world-leading sensitivity to weakly interacting massive particles (WIMPs) interacting via nuclear recoils with a ~7-tonne xenon target ...mass. This manuscript presents sensitivity projections to several low-energy signals of the complementary electron recoil signal type: 1) an effective neutrino magnetic moment and 2) an effective neutrino millicharge, both for pp-chain solar neutrinos, 3) an axion flux generated by the Sun, 4) axion-like particles forming the galactic dark matter, 5) hidden photons, 6) mirror dark matter, and 7) leptophilic dark matter. World-leading sensitivities are expected in each case, a result of the large 5.6t 1000d exposure and low expected rate of electron recoil backgrounds in the \(<\)100keV energy regime. A consistent signal generation, background model and profile-likelihood analysis framework is used throughout.
Two-phase xenon detectors, such as that at the core of the forthcoming LZ dark matter experiment, use photomultiplier tubes to sense the primary (S1) and secondary (S2) scintillation signals ...resulting from particle interactions in their liquid xenon target. This paper describes a simulation study exploring two techniques to lower the energy threshold of LZ to gain sensitivity to low-mass dark matter and astrophysical neutrinos, which will be applicable to other liquid xenon detectors. The energy threshold is determined by the number of detected S1 photons; typically, these must be recorded in three or more photomultiplier channels to avoid dark count coincidences that mimic real signals. To lower this threshold: a) we take advantage of the double photoelectron emission effect, whereby a single vacuum ultraviolet photon has a \(\sim20\%\) probability of ejecting two photoelectrons from a photomultiplier tube photocathode; and b) we drop the requirement of an S1 signal altogether, and use only the ionization signal, which can be detected more efficiently. For both techniques we develop signal and background models for the nominal exposure, and explore accompanying systematic effects, including the dependence on the free electron lifetime in the liquid xenon. When incorporating double photoelectron signals, we predict a factor of \(\sim 4\) sensitivity improvement to the dark matter-nucleon scattering cross-section at \(2.5\) GeV/c\(^2\), and a factor of \(\sim1.6\) increase in the solar \(^8\)B neutrino detection rate. Dropping the S1 requirement may allow sensitivity gains of two orders of magnitude in both cases. Finally, we apply these techniques to even lower masses by taking into account the atomic Migdal effect; this could lower the dark matter particle mass threshold to \(80\) MeV/c\(^2\).
The LUX-ZEPLIN dark matter search aims to achieve a sensitivity to the WIMP-nucleon spin-independent cross-section down to (1--2)\(\times10^{-12}\)\,pb at a WIMP mass of 40 GeV/\(c^2\). This paper ...describes the simulations framework that, along with radioactivity measurements, was used to support this projection, and also to provide mock data for validating reconstruction and analysis software. Of particular note are the event generators, which allow us to model the background radiation, and the detector response physics used in the production of raw signals, which can be converted into digitized waveforms similar to data from the operational detector. Inclusion of the detector response allows us to process simulated data using the same analysis routines as developed to process the experimental data.
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