Download or read book Extending the Physics Reach of the LUX and LZ Dark Matter Experiments by Lowering the Scintillation Threshold written by Nellie Marangou and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Background Modeling and First Searches for Low Energy Signals in The LUX ZEPLIN LZ Dark Matter Experiment written by Daniel Kodroff and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past half-century overwhelming evidence has mounted indicating the existence of a non-baryonic and enigmatic dark matter that constitutes approximately 85% of the total matter in the universe. Among the potential dark matter detection methods, dual- phase time projection chambers (TPCs) have emerged as the leading detector technology. LUX-ZEPLIN (LZ) is a direct detection dark matter experiment located at the 4850-ft depth level of the Sanford Underground Research Facility in South Dakota, USA, employing a 7 tonne active volume of liquid xenon in a dual-phase TPC. It's surrounded by an instrumented xenon "Skin" region and gadolinium-loaded liquid-scintillator outer detector, primarily serving as active vetoes for gamma-ray and neutron backgrounds, respectively, and contained within an ultra-pure water tank. The LZ detector began its first science run in December of 2021 and released its first results in the Summer of 2022. In order to ensure a low-background environment, a comprehensive material assay and selection campaign, for detector components, along with a xenon-purification campaign were pursued prior to and during construction. These mitigations have allowed LZ to achieve a background rate of 63.0 ± 4.5 x 10-6 events/keVee/kg/day in the low- energy region, approximately 60 times lower than that of its predecessor, the LUX experiment. LZ performed comprehensive measurements to constrain backgrounds in situ and construct a well-constrained time-dependent background model to use in searches for novel physics signals within this low-energy (
Download or read book Estimating LUX ZEPLIN s Sensitivity to Sub GeV Dark Matter Scattering Off Electrons in Xenon written by Gus Eberlein and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprising 85% of the mass of the universe, dark matter is one of the most pressing outstanding questions of physics. When it comes to directly detecting dark matter, the LUX-ZEPLIN (LZ) experiment has unparalleled sensitivity. We examine the detector's capability to detect sub-GeV dark matter scattering off the electrons in xenon, LZ's scintillation medium. We develop a signal model by calculating the expected DM-electron event rates as a function of electron recoil energy and as a function of the number of freed electrons. Alongside an established backgrounds model, this signal model is used to simulate events in the LZ detector. With this simulated data and a cut-and-count analysis, we are able to estimate cross sections of dark matter-electron scattering down to which LZ can detect the signal over the background. We find that LUX-ZEPLIN will be able to detect certain light dark matter models at a much greater sensitivity than previous direct detection experiments.
Download or read book Dark Matter Searches with the LUX and LZ Experiments written by Sally Shaw and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The LZ Dark Matter Experiment written by Kelly M Stifter and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to a compelling body of astrophysical and cosmological evidence, dark matter has come to be accepted as a crucial ingredient of modern cosmology, yet its physical nature remains one of the most pressing questions in the field of physics. One historically favored model of dark matter is weakly interacting massive particles, or WIMPs. LUX-ZEPLIN (LZ) is a next-generation dark matter detector designed to achieve field-leading sensitivity to much of the remaining accessible parameter space within the WIMP dark matter paradigm. To help realize the full-scale LZ detector, the System Test R&D platform was constructed at SLAC National Accelerator Laboratory to validate the performance of critical LZ subsystems at scales approaching or comparable to the LZ design. In this dissertation, I present results showing that the passivation of the high voltage electrodes in citric acid leads to a significant reduction in spontaneous emission of single electrons, potentially limiting a major instrumental background by up to several orders of magnitude and enabling a more sensitive dark matter search. The LZ detector has now been assembled at the Sanford Underground Research Facility (SURF) in Lead, South Dakota and is taking early data. I also give a first look at commissioning data that captured the first light from electrons in the LZ detector, and share methods to validate the in situ performance of the high voltage electrodes.
Download or read book Dark Matter Searches with the LUX and LZ Experiments written by S. Shaw and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurements of the LUX Trigger Efficiency written by Mongkol Moongweluwan and published by . This book was released on 2018 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Physicists discovered that all the known matter in the universe accounts for only about 5% of the total mass-energy of the universe. About 25% of the unknown matter, called dark matter, is missing. The remaining 70% is called dark energy. One of the most popular candidates for the dark matter is the Weakly Interacting Massive Particle (WIMP). WIMPs are theoretical particles that interact via the weak-nuclear and the gravitational forces. Its mass is in the order of 100 GeV/c2. Many detection technologies have been developed to search for WIMPs. The Large Underground Xenon experiment (LUX) uses a dual-phase xenon detector to search for WIMPs. The dual-phase xenon detector uses xenon in liquid and gaseous phases to detect interactions between WIMPs and xenon atoms. An event from a WIMP-xenon interaction consists of two light signals, called S1 and S2 signals. Successful data taking and subsequent analyses rely on an ability to correctly identify and record the S1 and S2 signals. LUX uses a trigger system developed at the University of Rochester for event selection. It is crucial to understand the performance of the trigger system and its impact on the data collected, so that the WIMP search results can be correctly interpreted. Many studies were carried to ensure that the performance and the functionality of the trigger system are understood. In the WIMP analysis, not only the WIMP-xenon interaction events are important, but also the background events. For WIMPs, which do not interact via the electromagnetic force, the interactions occur with the nucleus of the xenon atoms. This process is called nuclear recoil (NR). For background events, which are dominated by [gamma]-rays and electrons from beta-decays, the interactions occur mostly with the orbital electrons of the xenon atoms. This type of interaction is called electron recoil (ER). The trigger efficiency, which is defined as the probability that an event of interest is selected for offline analysis, is studied using raw data obtained from both ER and NR calibrations. The measured efficiency exceeds 98% at a pulse area of 90 detected photons, which is well below the WIMP analysis threshold on the S2 pulse area of 165 phd. The efficiency also exceeds 98% at recoil energies of 1.3 keV and above, for both ER and NR. The measured trigger efficiency varies between 99% and 100% over the fiducial volume of the detector. These efficiencies are sufficiently high for WIMP search analyses. The LUX experiment has been completed. The results from LUX yield no discovery of WIMPs and LUX has put a strong limit on the possible properties of WIMPs. The LUXZEPLIN experiment (LZ), which is a successor of LUX, is currently under construction. LZ will continue searching for WIMP and probe the WIMP property regions where LUX could not reach before."--Pages xiv-xv.
Download or read book Mitigation of Backgrounds for the Large Underground Xenon Dark Matter Experiment written by Chang Lee and published by . This book was released on 2015 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: While the existence of particle dark matter is widely accepted through multitude of astrophysics evidence, its exact nature remains mysterious. It is expected to comprise the local galactic halo, and one of the most favored candidates, weakly interacting massive particle (WIMP), is hypothesized to interact with baryonic matter. Such an interaction can be detected in a radio-quiet low-threshold detector such as the large underground xenon (LUX) detector. The LUX is a dual-phase xenon time projection chamber (TPC), and it operates at Sanford Underground Research Facility in Lead, SD. Analysis of the first science data with a 86.3 days live-time from LUX yielded the best spin-independent WIMP-nucleon cross-section exclusion limit to date, with the lower limit of $7.6\times10^{-46}$~cm$^2$ at 33~GeV/c$^2$ with a 90\% confidence level. This thesis consists the following chapters. The case for cold dark matter from the current cosmological observations is reviewed. The natures of the expected WIMP-nucleon scattering signal and the techniques to discriminate the background events are discussed. Principles of the dual-phase TPC are explained, with details of the LUX hardware. The original works for this thesis follows. A campaign to remove radioactive noble impurities from the target xenon is described in depth. A position reconstruction algorithm based on comparison of observed data to simulation is developed. Background events from the detector's internal walls are studied and modeled for the profile likelihood ratio test of the second analysis. Finally, the first published results are reviewed in detail.
Download or read book Characterizing the Peripheral Dynamics of Xenon Dark Matter Detectors written by Jacob Edward Cutter and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most important fundamental problems in physics today is to understand the nature of dark matter. The landscape of explanations for observed dark matter phenomena is vast and still expanding, and an impressive number of experiments have been built to probe the dark sector of the universe. A prominent class of detectors is aimed at discovering (or excluding) a particular kind of dark matter: the Weakly Interacting Massive Particle (WIMP). Searching for this popular dark matter candidate requires an ultra-sensitive, low-background target; xenon detectors serve as such a target for dark matter interactions. The Large Underground Xenon (LUX) detector is a dual-phase xenon time-projection chamber (TPC) which was operated underground at the Homestake Mine in Lead, South Dakota from 2013 to 2016, and was able to achieve the world's leading WIMP exclusion limit. However, successful reconstruction of WIMP-nucleus scatters in such detectors requires thorough understanding of the detection medium, which is made difficult by various confounding effects near the detector walls. Field-fringing is a major component of confusion in the periphery, and the large electric field non-uniformities in Run 4 of LUX provided a significant challenge in the dark matter analysis. Here is presented an algorithm to bijectively map between reconstructed event positions and true spatial coordinates, which serves as an important tool for studying field effects and fiducialization in LUX. Additionally, a successful dark matter search must model interfering background events in the WIMP search region which can't be directly vetoed. One class of unavoidable backgrounds comes from nuclear decay chain daughters in detector materials themselves, which may produce WIMP-like signals (an effect which is amplified due to various detector effects). The Davis Xenon (DAX) test bed system and a dual-phase TPC have been assembled and operated at UC Davis to characterize these common "wall backgrounds", as well as perform other R&D studies for the next-generation LUX-ZEPLIN (LZ) experiment. The DAX TPC specifically measures the xenon response to heavy nuclei produced by custom [alpha] decay sources created using novel chemical deposition procedures. In this thesis, results will be presented for the light and charge yields of immersed localized sources of 206Pb ions in liquid xenon, as well as a method for tagging such recoil events in situ by using PIN diodes as charged particle detectors to capture the correlated [alpha] particles. We also compare our isolated 206Pb events with previous WIMP search data from LUX, and discuss the significance of 206Pb as a WIMP background. Such information is most useful to future experiments if it can improve existing background models and simulations. The Noble Element Simulation Technique (NEST) is the ultimate software package for calculating expected signal yields in xenon detectors, but is an empirical framework that relies on experimental data to inform the models. We discuss the development of current NEST v2 models, specifically the heavy nuclear recoil models, as well as our current understanding of the xenon microphysics. We also show NEST predictions for mono-energetic 206Pb recoils, and discuss how our most recent DAX 206Pb measurements may inform NEST models in future work.
Download or read book Background and Sensitivity Studies for the LUX ZEPLIN Dark Matter Experiment written by Umit Utku and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pulse Shape Discrimination in the LUX Dark Matter Detector written by Dev Ashish Khaitan and published by . This book was released on 2019 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Abundant evidence from astrophysical and cosmological observations suggests 80% of the total matter density in the Universe is in the form of dark matter (DM). This matter is not described by the Standard Model (SM) and numerous candidates have been proposed. Weakly Interacting Massive Particles (WIMPs) are one of the leading DM candidates. The Large Underground Xenon (LUX) experiment was built to directly observe the interaction of DM with xenon target nuclei. LUX acquired data between April 2013 until August 2016 at Sanford Underground Research Facility (SURF) in Lead, South Dakota. The analysis of this data led to the publication of numerous world-leading upper limits on the WIMP-nucleon scattering cross-section. WIMPs are expected to produce nuclear recoil (NR) events within liquid xenon time-projection chambers. We present a measurement of the scintillation timing characteristics of liquid xenon in the LUX dark matter detector and develop a pulse shape discriminant to be used for particle identification. To accurately measure the timing characteristics, we develop a template-fitting method to reconstruct the detection times of photons. Analyzing calibration data collected during the 2013-16 LUX WIMP search, we provide a new measurement of the singlet-to-triplet scintillation ratio for electron recoils (ER) below 46 keV, and we make a first-ever measurement of the NR singlet-to-triplet ratio at recoil energies below 74 keV. We exploit the difference of the photon time spectra for NR and ER events by using a prompt fraction discrimination parameter, which is optimized using calibration data to have the least number of ER events that occur in the 50% NR acceptance region. We then demonstrate how this discriminant can be used in conjunction with the charge-to-light discrimination to improve the signal-to-noise ratio for NRs"--Pages xii-xiii.
Download or read book The LZ Dark Matter Search and Development of a New Gas Phase Technique to Characterize Low Level Electron Emission from Electrode Grids written by Wei Ji and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dark Matter is needed to explain many cosmological observations and therefore has been proposed for many decades, but it awaits direct detection. One of the most popular classes of dark matter candidates is Weakly Interacting Massive Particles (WIMPs), which have masses in the order of 100 GeV and couple to ordinary matter at weak scale. In WIMP direct detection experiments, we look for WIMPs being scattered by nuclei, a process which produces low energy (smaller than 100 keV) recoiling nuclei that can be observed. We are building LZ, a detector looking for WIMPs using liquid xenon in a dual-phase time projection chamber (TPC), at 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. LZ aims to achieve the world's highest sensitivity to find WIMPs via WIMP-nucleon interactions. After a brief discussion of dark matter and the LZ experiment, this dissertation presents the details of my study to solve the electron emission problem. The LZ TPC will consist of electrode grids and other metallic surfaces that can emit electrons when operated under voltage. Because the charge measurement in the LZ detector is sensitive to single electrons, electrons from the grids can be both a significant nuisance for data collection and a source of background at low-energies, limiting the sensitivity of the experiment for low-mass WIMPs. This has motivated us to develop a test detector to study how to reduce this background. The test detector consists of a pair of grids biased to high voltage and operated in xenon gas. The electric field between the grid causes the electrons to produce electroluminescence scintillation light that is measured by PMTs. This new technique is sensitive to single electrons emitted by the grids, allowing a measurement of emission currents as low as atto-amperes. We used this detector to study the properties of different grids and to determine what treatments can be done to reduce their electron emission. We found that passivation with citric acid reduces electron emission from stainless steel surfaces. This work was supervised by Professor Thomas Shutt and was completed in collaboration with members of the LZ collaboration and the SLAC LZ group.
Download or read book Early Career written by and published by . This book was released on 2017 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report results from a search for weakly interacting dark matter particles obtained with the LUX experiment. LUX was located at a depth of 4850 feet at the Sanford Underground Research Facility in Lead, South Dakota from 2013 through 2016. It found no evidence for dark matter particle interactions and set new constraints on the properties of such particles for masses between 6 GeV and 100 TeV. The work reported here also characterized the performance of such experiments by developing a new calibration technique based upon a tritium beta decay source.
Download or read book Photoneutron Sources written by B. W. Sargent and published by . This book was released on 1946 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Noble Gas Detectors written by Elena Aprile and published by John Wiley & Sons. This book was released on 2007-02-27 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the physical properties of noble fluids, operational principles of detectors based on these media, and the best technical solutions to the design of these detectors. Essential attention is given to detector technology: purification methods and monitoring of purity, information readout methods, electronics, detection of hard ultra-violet light emission, selection of materials, cryogenics etc. The book is mostly addressed to physicists and graduate students involved in the preparation of fundamental next generation experiments, nuclear engineers developing instrumentation for national nuclear security and for monitoring nuclear materials.
Download or read book Neutrino Physics written by E. Bellotti and published by IOS Press. This book was released on 2003-12-08 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutrino physics contributed in an fundamental way to the progress of science, opening important windows of knowledge in elementary particle physics, as well in astrophysics and cosmology. Substantial experimental efforts are presently dedicated to improve our knowledge on neutrino properties as, in fact, we don't know yet some of the basic ones. Although very significant steps forward have been done, neutrino masses and mixings still remain largely unknown and constitute an important field for future research. Are neutrinos Majorana or Dirac particles? Have they a magnetic moment? Historically, studies on weak processes and, therefore, on neutrino physics, provided first the Fermi theory of weak interactions and then the V-A theory. Finally, the observation of weak neutral currents provided the first experimental evidence for unification of weak and electromagnetic interactions by the so called "Standard Model' of elementary particles. In addition to the results obtained from the measurement of the solar neutrino flux, the study of atmospheric neutrinos strongly supports the hypothesis of neutrino oscillation among different flavours. At the same time, the detection of neutrinos emitted by our Sun gave an important confirmation that the Sun produces energy via a chain of nuclear reactions; in particular in our Sun a specific cycle - the hydrogen cycle - is responsible for practically all the produced energy.
Download or read book Illuminating Dark Matter written by Rouven Essig and published by Springer Nature. This book was released on 2019-11-22 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on a Simons Symposium held in 2018, the proceedings in this volume focus on the theoretical, numerical, and observational quest for dark matter in the universe. Present ground-based and satellite searches have so far severely constrained the long-proposed theoretical models for dark matter. Nevertheless, there is continuously growing astrophysical and cosmological evidence for its existence. To address present and future developments in the field, novel ideas, theories, and approaches are called for. The symposium gathered together a new generation of experts pursuing innovative, more complex theories of dark matter than previously considered.This is being done hand in hand with experts in numerical astrophysical simulations and observational techniques—all paramount for deciphering the nature of dark matter. The proceedings volume provides coverage of the most advanced stage of understanding dark matter in various new frameworks. The collection will be useful for graduate students, postdocs, and investigators interested in cutting-edge research on one of the biggest mysteries of our universe.
