Browsing by Author "Piepke, Andreas"
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Item Antineutrino neutral current interactions in MiniBooNE(University of Alabama Libraries, 2012) Dharmapalan, Ranjan; Stancu, Ion; University of Alabama TuscaloosaThe antineutrino nucleon neutral current elastic scattering cross section measured at the MiniBooNE experiment is reported. The data set corresponds to 10.1 × 10^20 protons on target which is a world record neutral current elastic antineutrino sample. An antineutrino to neutrino neutral current scattering cross section ratio is measured after accounting for all associated errors. This is the first time such a ratio has been experimentally reported. Previous MiniBooNE neutrino cross section measurements have indicated a higher value for the axial mass, M_A, as compared to the nominal value of M_A=1.0 GeV. A Χ^2 test was performed to find the best value of M_A which matches the antineutrino neutral current elastic data. Finally, an exciting possibility to search for dark matter in the MiniBooNE experiment, using the neutral current interactions is discussedItem An Apparatus to Manipulate and Identify Individual Ba Ions from Bulk Liquid Xe(2014-09-23) Piepke, Andreas; University of Alabama TuscaloosaWe describe a system to transport and identify barium ions produced in liquid xenon, as part of R&D towards the second phase of a double beta decay experiment, nEXO. The goal is to identify the Ba ion resulting from an extremely rare nuclear decay of the isotope ^136Xe, hence providing a confirmation of the occurrence of the decay. This is achieved through Resonance Ionization Spectroscopy (RIS). In the test setup described here, Ba ions can be produced in liquid xenon or vacuum and collected on a clean substrate. This substrate is then removed to an analysis chamber under vacuum, where laser-induced thermal desorption and RIS are used with time-of-flight mass spectroscopy for positive identification of the barium decay product.Item ⁷Be Solar Neutrino Measurement with KamLAND(2015-11-30) Piepke, Andreas; University of Alabama TuscaloosaWe report a measurement of the neutrino-electron elastic scattering rate of 862 keV ⁷Be solar neutrinos based on a 165.4 kt d exposure of KamLAND. The observed rate is 592 ± 94 (kt d)⁻¹, which corresponds to an 862-keV ⁷Be solar neutrino flux of (3.26 ± 0.52) × 10⁹ cm⁻²s⁻¹, assuming a pure electron-flavor flux. Comparing this flux with the standard solar model prediction and further assuming three-flavor mixing, a vₑ survival probability of 0.66 ± 0.15 is determined from the KamLAND data. Utilizing a global three-flavor oscillation analysis, we obtain a total ⁷Be solar neutrino flux of (5.82 ± 1.02) × 10⁹ cm⁻²s⁻¹, which is consistent with the standard solar model predictions.Item Constraining Radon Backgrounds in LZ(2018-01-03) Piepke, Andreas; University of Alabama TuscaloosaThe LZ dark matter detector, like many other rare-event searches, will suffer from backgrounds due to the radioactive decay of radon daughters. In order to achieve its science goals, the concentration of radon within the xenon should not exceed 2 µBq/kg, or 20 mBq total within its 10 tonnes. The LZ collaboration is in the midst of a program to screen all significant components in contact with the xenon. The four institutions involved in this effort have begun sharing two cross-calibration sources to ensure consistent measurement results across multiple distinct devices. We present here five preliminary screening results, some mitigation strategies that will reduce the amount of radon produced by the most problematic components, and a summary of the current estimate of radon emanation throughout the detector. This best estimate totals < 17.3 mBq, sufficiently low to meet the detector’s science goals.Item Correlated Fluctuations Between Luminescence and Ionization in Liquid Xenon(2003-08-01) Piepke, Andreas; University of Alabama TuscaloosaThe ionization of liquefied noble gases by radiation is known to be accompanied by fluctuations much larger than predicted by Poisson statistics. We have studied the fluctuations of both scintillation and ionization in liquid xenon and have measured a strong anti-correlation between the two at a microscopic level, with coefficient −0.80 < ρep < −0.60. This provides direct experimental evidence that electron-ion recombination is partially responsible for the anomalously large fluctuations and at the same time allows substantial improvement of calorimetric energy resolution.Item Detection of Very Small Neutrino Masses in Double-Beta Decay Using Laser Tagging(2000-05-04) Piepke, Andreas; University of Alabama TuscaloosaWe describe an approach to the study of neutrino masses that combines quantum optics techniques with radiation detectors to obtain unprecedented sensitivity. With it the search for Majorana neutrino masses down to ∼10 meV will become accessible. The experimental technique uses the possibility of individually detecting Ba⁺-ions in the final state of ¹³⁶Xe double-beta decay via resonant excitation with a set of lasers aimed at a specific location in a large Time Projection Chamber. The specificity of the atomic levels provides tagging and, together with more traditional event recognition parameters, greatly suppresses radioactive backgrounds.Item Double Beta Decay of ⁴⁸Ca(1996-12-23) Piepke, Andreas; University of Alabama Tuscaloosa⁴⁸Ca, the lightest experimentally accessible double beta decay candidate, is the only one simple enough to be treated exactly in the nuclear shell model. Thus the ββ₂ᵥ half-life measurement, reported here, provides a unique test of the nuclear physics involved in the ββ matrix element calculation. Enriched ⁴⁸Ca sources of two different thicknesses have been exposed in a time projection chamber. We observe a half-life of T²ᵛ₁/₂ = (4.3⁺².⁴₋₁.₁[stat] ± 1.4[syst]) × 10¹⁹ yr consistent with shell model calculations.Item First observation of 7Be solar neutrinos with KamLAND(University of Alabama Libraries, 2009) Keefer, Gregory John; Piepke, Andreas; University of Alabama TuscaloosaThe international KamLAND collaboration operates a 1 kton liquid scintillation detector in the Kamioka mine in Gifu, Japan. KamLAND's main scientific results are the precision measurement of the solar Δm²₁₂ = 7.58 + +0.14-0.13 stat± 0.15syst and tan² θ₁₂ = 0.56+0.10 -0.07 stat+0.10-0.06 syst utilizing reactor antinuetrinos and first evidence for the observation of geologically produced antineutrinos. In an effort to extend KamLAND's scientific reach, extensive research has been performed on preparing a spectroscopic measurement of ⁷Be solar neutrinos. This work provides the first inclusive analysis of KamLAND's backgrounds below 1 MeV. ⁸⁵Kr and ²¹⁰Pb, dissolved in KamLAND liquid scintillator, were found to be the dominant source of low energy backgrounds. The concentration of these ultra-trace contaminants were determined to be 10⁻²⁰ g/g. This is more then 6 orders of magnitude lower then commercially available ultra-pure liquids. To attain a signal-to-background ratio suitable for the detection of ⁷Be solar neutrinos, the concentration of these contaminants had to be reduced by 5 orders of magnitude. A comprehensive study of ²¹⁰Pb removal was undertaken over the course of this thesis. This work further covers techniques for the removal of ²²⁰Rn, ²²²Rn and their daughter nuclei from liquid scintillator at concentrations of 10⁻¹⁸ g/g . Purification techniques studied in this work include water extraction, isotope exchange, adsorption, and distillation. These laboratory studies guided the design and implementation of a large scale purification system in the Kamioka mine. The purification system's design and operation is discussed in detail as well as specific experiments devised to control scintillator quality and radio-purity. The purification system's effectiveness in removing radioactive trace impurities is analyzed in detail. The total scintillator purified over two years of operation was more then 4.6 ktons. It is shown here that the KamLAND collaboration has successfully reduced the ⁸⁵Kr specific activity of the scintillator by a factor of 2.6 x 10⁴ while ²¹⁰Bi was reduced by a factor 2 x 10³. Due to the success in reducing the intrinsic backgrounds through multiple purifications, this work provides the first evidence for a ⁷Be solar neutrino signal in KamLAND. The presented analysis covers 5.448 kton-days of exposure time. While the current work is not yet providing a robust measurement of the ⁷Be solar neutrino flux, the presence of ⁷Be solar neutrino is shown to be statistically preferred over a null hypothesis.Item First Results from KamLAND: Evidence for Reactor Antineutrino Disappearance(2003-01-17) Piepke, Andreas; University of Alabama TuscaloosaKamLAND has measured the flux of v̅ₑ’s from distant nuclear reactors. We find fewer v̅ₑ events than expected from standard assumptions about v̅ₑ propagation at the 99.95% C.L. In a 162 ton ∙ yr exposure the ratio of the observed inverse β-decay events to the expected number without v̅ₑ disappearance is 0.611 ± 0.085(stat) ± 0.041(syst) for v̅ₑ energies ˃ 3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the “large mixing angle” region are excluded.Item Gauge & Higgs Boson Summary Table(Elsevier, 2004-07-15) Piepke, Andreas; University of Alabama TuscaloosaItem Investigation of the Majoron-Accompanied Double-Beta Decay Mode of ⁷⁶Ge(1993-05-10) Piepke, Andreas; University of Alabama TuscaloosaWe have examined the double-beta decay mode accompanied by Majoron emission. After 223 days of measurement corresponding to about 615 kg d or 19.3 mol yr of exposure we find a lower half-life limit for this decay channel of T⁰ᵛˣ₁/₂ ˃ 1.66(1.99) × 10²² yr [90% (68%) C.L.] yielding a new limit for the Majoron-neutrino coupling of 〈 gᵥₓ 〉 < 1.8 × 10⁻⁴ (90% C.L.).Item KamLAND Sensitivity to Neutrinos from Pre-Supernova Stars(2016-02-10) Piepke, Andreas; University of Alabama TuscaloosaIn the late stages of nuclear burning for massive stars (M > 8 M⊙), the production of neutrino–antineutrino pairs through various processes becomes the dominant stellar cooling mechanism. As the star evolves, the energy of these neutrinos increases and in the days preceding the supernova a significant fraction of emitted electron anti-neutrinos exceeds the energy threshold for inverse beta decay on free hydrogen. This is the golden channel for liquid scintillator detectors because the coincidence signature allows for significant reductions in background signals. We find that the kiloton-scale liquid scintillator detector KamLAND can detect these pre-supernova neutrinos from a star with a mass of 25 M⊙ at a distance less than 690 pc with 3σ significance before the supernova. This limit is dependent on the neutrino mass ordering and background levels. KamLAND takes data continuously and can provide a supernova alert to the community.Item Measurement of the ⁸B Solar Neutrino Flux with the KamLAND Liquid Scintillator Detector(2011-09-13) Piepke, Andreas; University of Alabama TuscaloosaWe report a measurement of the neutrino-electron elastic scattering rate from ⁸B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5-MeV analysis threshold is 1.49 ± 0.14(stat) ± 0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a ⁸B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77 ± 0.26(stat) ± 0.32(syst) × 10⁶ cm⁻²s⁻¹. The analysis threshold is driven by ²⁰⁸Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic ¹¹Be. The measured rate is consistent with existing measurements and with standard solar model predictions which include matter-enhanced neutrino oscillation.Item Measuring the neutrino mixing angle theta-13 with the double chooz far detector(University of Alabama Libraries, 2012) Ostrovskiy, Igor; Busenitz, Jerome K.; University of Alabama TuscaloosaThe neutrino mixing angle theta-13 is the last one which value is still unknown. This dissertation presents an analysis suggesting a non-zero value of the theta-13. The analysis is based on four months of data taken with the far Double Chooz reactor anti-neutrino detector. Using only rate information yields a best fit value of sin2(2theta-13) equal to 0.0934±0.0785 (1 sigma). Incorporating information on the shape of the signal energy spectrum in the analysis results in a best fit value of 0.0849±0.0509 (1 sigma). Based on frequentist studies, sin2(2theta-13)=0 is excluded at the 92.6% confidence level. The frequentist construction using delta chi-square as an ordering rule gives [0.0098, 0.1825] interval for sin2(2theta-13) at 90% C.L.Item A Monte Carlo approach to 7Be solar neutrino analysis with KamLAND(University of Alabama Libraries, 2012) Grant, Christopher; Piepke, Andreas; University of Alabama TuscaloosaTerrestrial measurements of neutrinos produced by the Sun have been of great interest for over half a century because of their ability to test the accuracy of solar models. The first solar neutrinos detected with KamLAND provided a measurement of the ^8B solar neutrino interaction rate above an analysis threshold of 5.5 MeV. This work describes efforts to extend KamLAND's detection sensitivity to solar neutrinos below 1 MeV, more specifically, those produced with an energy of 0.862 MeV from the ^7Be electron-capture decay. Many of the difficulties in measuring solar neutrinos below 1 MeV arise from backgrounds caused abundantly by both naturally occuring, and man-made, radioactive nuclides. The primary nuclides of concern were ^210Bi, ^85Kr, and ^39Ar. Since May of 2007, the KamLAND experiment has undergone two separate purification campaigns. During both campaigns a total of 5.4 ktons (about 6440 m^3) of scintillator was circulated through a purification system, which utilized fractional distillation and nitrogen purging. After the purification campaign, reduction factors of 1.5 x 10^3 for ^210Bi and 6.5 x 10^4 for ^85Kr were observed. The reduction of the backgrounds provided a unique opportunity to observe the ^7Be solar neutrino rate in KamLAND. An observation required detailed knowledge of the detector response at low energies, and to accomplish this, a full detector Monte Carlo simulation, called KLG4sim, was utilized. The optical model of the simulation was tuned to match the detector response observed in data after purification, and the software was optimized for the simulation of internal backgrounds used in the ^7Be solar neutrino analysis. The results of this tuning and estimates from simulations of the internal backgrounds and external backgrounds caused by radioactivity on the detector components are presented. The first KamLAND analysis based on Monte Carlo simulations in the energy region below 2 MeV is shown here. The comparison of the Δχ^2 between the null hypothesis and the existence of the ^7Be solar neutrino signal in the data shows a change of 27.9 units, providing evidence that the signal is statistically favored. This analysis reports a measured interaction rate from ^7Be solar neutrinos of R = 343.3 ± 65.0(stat) ± 99.2(syst) events/(kton·day), which corresponds to a total flux of ɸ = (3.41 ±; 1.18) x 10^9 cm^-2 s^-1. The ^7Be solar neutrino flux reported in this work is only the second measurement made of this quantity worldwide. It provides an important cross-check of the Borexino experiment. The flux measurement reported here agrees within 1σ with the standard solar model predictions thus validating our basic understanding of solar fusion reaction processes.Item Neutrino-nucleus neutral current elastic interactions measurement in MiniBooNE(University of Alabama Libraries, 2010) Perevalov, Denis; Stancu, Ion; University of Alabama TuscaloosaThe MiniBooNE experiment at the Fermi National Accelerator Laboratory (Fermilab) was designed to search for electron to muon neutrino oscillations at Delta m^2~1 eV^2 using an intense neutrino flux with an average energy of about 700 MeV. From 2002 to 2009 MiniBooNE has accumulated more than 1.0x10^{21} protons on target (POT) in both neutrino and antineutrino modes. MiniBooNE provides a perfect platform for detailed measurements of exclusive and semiinclusive neutrino cross-sections, for which MiniBooNE has the largest samples of events up to date, such as neutral current elastic (NCE), neutral current pi^0, charged current quasi-elastic (CCQE), charged current pi^+, and other channels. These measured cross-sections, in turn, allow to improve the knowledge of nucleon structure. This thesis is devoted to the study of NCE interactions. Neutrino-nucleus neutral current elastic scattering accounts for about 18% of all neutrino interactions in MiniBooNE. Using a high-statistics, high purity sample of NCE interactions in MiniBooNE, the flux-averaged NCE differential cross-section has been measured and is being reported here. Further study of the NCE cross-section allowed for probing the structure of nuclei. The main interest in the NCE cross-section is that it may be sensitive to the strange quark contribution to the nucleon spin, $Delta s$, this however requires a separation of NCE proton from NCE neutron events, which in general is a challenging task. MiniBooNE uses a Cherenkov detector, which imposes restrictions on the measured nucleon kinematic variables, mainly due to the impossibility to reconstruct the nucleon direction below the Cherenkov threshold. However, at kinetic energies above this threshold MiniBooNE is able to identify NCE proton events that do not experience final state interactions. These events were used for the $Delta s$ measurement. In this thesis MiniBooNE reports the NCE (n+p) cross-section, the measurement of the axial mass, $M_A$, and the $Delta s$ parameter from the NCE data.Item Prospects for Barium Tagging in Gaseous Xenon(2011-08-10) Piepke, Andreas; University of Alabama TuscaloosaTagging events with the coincident detection of a barium ion would greatly reduce the background for a neutrino-less double beta decay search in xenon. This paper describes progress towards realizing this goal. It outlines a source that can produce large quantities of Ba++ in gas, shows that this can be extracted to vacuum, and demonstrates a mechanism by which the Ba++ can be efficiently converted to Ba+ as required for laser identification.Item Radon Detection and 241Am-7Li Source Development for the Lux-Zeplin Dark Matter Experiment(University of Alabama Libraries, 2025) Sazzad, A. B. M. Rafi; Piepke, AndreasDark matter presents a conundrum at the intersection of particle physics and cosmology. Observational data from astronomy and precision cosmology have allowed scientists to calculate the relic abundance of dark matter with considerable accuracy. Yet, the exact nature of the dark matter particle remains a mystery. Theoretical models and hypotheses suggest that the mass of dark matter particle candidates ranges from as low as $10⁻²² eV/c² to as high as 10³ M_⊙(10⁷⁰ eV/c², spanning an astounding ~90 orders of magnitude! Of the numerous candidate particles, those that also resolve issues in the highly successful standard model of particle physics, are of particular interest to experimentalists. One such candidate is the Weakly Interacting Massive Particle (WIMP), which if it exists, could also resolve the gauge hierarchy problem in particle physics. WIMPs are theorized to interact with certain detector materials such as liquid xenon (LXe), via the weak force, active on all other known particles, and produce nuclear recoil (NR). However, this detection scheme meets several challenges. Firstly, the LXe must be sufficiently purified of radioactive impurities like ⁸⁵Kr and ²²²Rn to not overwhelm the rare NR signal events in terms of interaction rate. Secondly, the detector requires precise calibration of its response to NR-type interactions, specifically in the energy region where WIMP interactions are expected. In this thesis, I describe my contributions to the ongoing direct dark matter search experiment called LUX-ZEPLIN (LZ). Most of my work relates to the preparation of the experiment, namely the measurement of the release of trace amounts of radon gas from detector materials, forming the dominant background component. This work was important to ensure a low detector background and, with it, high sensitivity to dark matter. As a second contribution, I participated in all phases of the development, manufacture, testing and calibration of AmLi neutron sources important for mapping out the NR band for WIMP detection. Both subjects have been documented in publications with me as the first author; the work was performed at UA. The thesis, furthermore, describes my data analysis effort, utilizing AmLi source calibration data to help establish the WIMP event parameter range in LZ.Item Recent Double Beta Decay Results(American Institute of Physics, 2008-05-29) Piepke, Andreas; University of Alabama TuscaloosaThe status and recent results of second generation ββ‐experiments using isotopically enriched source materials are described. These experiments are at present the most sensitive tools to distinguish Dirac from Majorana neutrinos. The at present most advanced experimental techniques, namely the use of high‐resolution calorimetric detectors and of time projection chambers are compared. New limits on the Majorana neutrino mass as well as for the Majoron‐neutrino coupling are presented.Item REVIEW OF PARTICLE PHYSICS Particle Data Group(IOP Publishing Ltd, 2016) Piepke, Andreas; University of Alabama TuscaloosaThe Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 3,062 new measurements from 721 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 117 reviews are many that are new or heavily revised, including those on Pentaquarks and Inflation.The complete Review is published online in a journal and on the website of the Particle Data Group (http://pdg.lbl.gov). The printed PDG Book contains the Summary Tables and all review articles but no longer includes the detailed tables from the Particle Listings. A Booklet with the Summary Tables and abbreviated versions of some of the review articles is also available.