Axion Dark Matter and Two-neutrino Double Electron Capture Searches in the Large Underground Xenon Experiment PDF Download

Author: Maria Francesca Marzioni
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Jingqiang Ye
Publisher:
ISBN:
Category :
Languages : en
Pages : 208

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Numerous evidence suggests that the majority of matter in the Universe is made of a rarely interacting, non-luminous component, termed dark matter. The XENON1T experiment, utilizing a two-phase liquid xenon time projection chamber, was primarily designed to search for Weakly Interacting Massive Particles (WIMPs), one of the most promising dark matter candidates. With one tonne-year exposure, XENON1T placed the most stringent upper limits of WIMP interaction strength for a large range of WIMP masses and a variety of interaction types. The unprecedented low background in XENON1T also enabled competitive searches for electronic recoil signals. An excess was observed above the known background at low energies and is most prominent between 2 and 3 keVee. This excess favors solar axions over backgrounds at 3.4 sigma, a hypothetical particle arising from the Peccei-Quinn theory to solve the strong CP problem. The resulting axion couplings, however, are in strong tension with astrophysical constraints. The excess can also be explained by beta decays of tritium at 3.2 sigma with a trace amount, which can neither be confirmed nor be rejected with the current knowledge of its production and mitigation mechanisms. If an unconstrained tritium component is added to both alternate and null hypotheses, the significance of the solar axion hypothesis is reduced to 2.0 sigma. This search also includes other electronic recoil signals, such as an enhanced neutrino magnetic moment, bosonic dark matter, and leptophilic dark matter. The prospect of XENONnT, the next-generation experiment that is expected to take science data in 2021, is also discussed in the context of searching for WIMPs and deciphering the excess observed in XENON1T, respectively.

Author: Jacob Edward Cutter
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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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.

Author: Chang Lee
Publisher:
ISBN:
Category : Astrophysics
Languages : en
Pages : 217

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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.

Author:
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ISBN:
Category :
Languages : en
Pages : 8

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Xenon has recently been the medium of choice in several large scale detectors searching for WIMP dark matter and neutrinoless double beta decay. Though present-day large scale experiments use liquid xenon, the gas phase offers advantages favorable to both types of searches such as improved intrinsic energy resolution and fewer fluctuations in the partition of deposited energy between scintillation and ionization channels. We recently constructed a high pressure xenon gas TPC as a prototype for the NEXT (Neutrino Experiment with a Xenon TPC) neutrinoless double beta decay experiment and have demonstrated the feasibility of 0.5% FWHM energy resolution at the 136Xe double beta Q-value with 3-D tracking capabilities. We now present results from this prototype on the simultaneous observation of cintillation and ionization produced by nuclear recoils at approximately 14 bar pressure. The recoils were produced by neutrons of approximately 2-6 MeV emitted from a radioisotope plutonium-beryllium source, and primary scintillation (S1) and electroluminescent photons produced by ionization (S2) were observed. We discuss the potential of gaseous xenon to distinguish between electron and nuclear recoils through the ratio of these two signals S2/S1. From these results combined with the possibility of using columnar recombination to sense nuclear recoil directionality at high pressures we envision a dual-purpose, ton-scale gaseous xenon detector capable of a combined search for WIMP dark matter and neutrinoless double beta decay. This work has been performed within the context of the NEXT collaboration.

Author: Sergey Uvarov
Publisher:
ISBN: 9781369796834
Category :
Languages : en
Pages :

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Cosmological observations overwhelmingly support the existence of dark matter which constitutes 87% of the universe's total mass. Weakly Interacting Massive Particles (WIMPs) are a prime candidate for dark matter, and the Large Underground Xenon (LUX) experiment aims to a direct-detection of a WIMP-nucleon interaction. The LUX detector is a dual-phase xenon time-projection chamber housed 4,850 feet underground at Sanford Underground Research Facility in Lead, South Dakota. We present the ionization-only analysis of the LUX 2013 WIMP search data. In the 1.04 x 104 kg-days exposure, thirty events were observed out of the 24.8 expected from radioactive backgrounds. We employ a cut-and-count method to set a 1-sided 90% C.L. upper limit for spin-independent WIMP-nucleon cross-sections. A zero charge yield for nuclear-recoils below 0.7 keV is included upper limit calculation. This ionization-only analysis excludes an unexplored region of WIMP-nucleon cross-section for low-mass WIMPs achieving 1.56 x 10−43 cm2 WIMP-nucleon cross-section exclusion for a 5.1 GeV/c2 WIMP.

Author:
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ISBN:
Category :
Languages : en
Pages : 12

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This research project is a collaboration with the axion search experiment at Lawrence Livermore National Laboratory. The axion is a particle that affects two important issues in particle physics and astrophysics: the origin of CP symmetry in the strong interactions, and the composition of the dark-matter of the universe. First predicted in 1978, present laboratory, astrophysical, and cosmological constraints suggest axions have a mass in the 1 [mu]eV-1 meV range. Axions are especially significant as dark matter if their mass is in the range 1-10 [mu]eV. These dark matter axions may be detected by their coupling to photons through the E - B interaction in a tunable high-Q microwave cavity permeated by a strong external magnetic field. The present experiment is the first cavity experiment with the sensitivity to possibly observe cosmic axions. It has recently begun taking data and will operate for the next several years. The University of Florida plans to contribute to the operation of this detector and to the design and prototyping of cavities for the experiment.

Author: Jeremy Allen Mock
Publisher:
ISBN: 9781321609462
Category :
Languages : en
Pages :

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The Weakly Interacting Massive Particles (WIMP) has been postulated as a candidate that constitutes dark matter, which dominates the matter density in the universe. The Large Underground Xenon (LUX) detector is a 370 kg (112 kg fiducial) dual-phase xenon time projection chamber operating 4,850 feet underground at the Sanford Underground Research Facility in Lead, South Dakota with the goal of detecting WIMPs. A refined understanding of detector response is required in order to make such searches more sophisticated. The LUX simulation includes a new physics model, the Noble Element Simulation Technique, which accurately predicts the scintillation and ionization yields as well as the prompt and electroluminescence pulse shapes in xenon. These models, combined with a new technique for in-situ, low-energy neutron calibration, allow for the extension of the WIMP detection regime into a lower-energy region. A novel analysis technique for the removal of spurious, high-rate background events facilitates the reduction of conservative analysis thresholds. Both of these improvements, which lead to an increased sensitivity of LUX to low-mass WIMPs, are described in this thesis. While no discovery is reported, this work establishes the most stringent 90% confidence level upper limit on the WIMP-nucleon cross-section of 7.43 x 10−46 cm2 for a WIMP with mass 33 GeV/c2.

Author: Nirmala Prakash
Publisher: World Scientific
ISBN: 9814449202
Category : Science
Languages : en
Pages : 674

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Book Description
Dark Matter, Neutrinos, and Our Solar System is a unique enterprise that should be viewed as an important contribution to our understanding of dark matter, neutrinos and the solar system. It describes these issues in terms of links, between cosmology, particle and nuclear physics, as well as between cosmology, atmospheric and terrestrial physics. It studies the constituents of dark matter (classified as hot warm and cold) first in terms of their individual structures (baryonic and non-baryonic, massive and non-massive, interacting and non-interacting) and second, in terms of facilities available to detect these structures (large and small). Neutrinos (an important component of dark matter) are treated as a separate entity. A detailed study of these elusive (sub-atomic) particles is done, from the year 1913 when they were found as byproducts of beta decay — until the discovery in 2007 which confirmed that neutrino flavors were not more than three (as speculated by some).The last chapter of the book details the real-time stories about the “regions” that were not explored thus far, for lack of advanced technology. Their untold fascinating stories (which span up to 2010) are illustrated here datewise in full.The book concludes with the latest news that the Large Hadron Collider team at CERN has finally succeeded in producing 7 trillion electronic Volts of energy by creating head-on-collisions of protons and more protons (in search of God-particle). The energy produced was three times more than previous records.

Author: Douglas R. Tiedt
Publisher:
ISBN:
Category : Dark matter (Astronomy)
Languages : en
Pages : 266

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Cosmological observations of the universe find a stark mismatch between the expected levels of visible matter and the state of the universe. Rotational velocities of galaxies, interactions of galaxy clusters, and the cosmic microwave background (CMB) all point to the existence of some kind of \dark matter" that primarily interacts gravitationally. One theory for the nature of this matter is the Weakly Interacting Massive Particle (WIMP), whose existence is predicted both by extensions to the particle physics standard model, and by straightforward thermodynamic arguments following the expansion and cooling of the early universe. The search for dark matter in our labs has become critical in order to understand its true nature. The Large Underground Xenon (LUX) dark matter detector operated at the Sanford Underground Research Facility (SURF) for several years until it was decommissioned in 2016. It was a two-phase time projection chamber (TPC) that used 370 kg of xenon to search for the nuclear recoil signature of WIMPs.