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Author: Alexis G. Schubert Publisher: ISBN: Category : Languages : en Pages : 350
Book Description
The neutrino, an elementary particle, has been the subject of experimental investigation for over 50 years. Recent experiments have shown that neutrinos have mass and oscillate, but questions about fundamental properties of the neutrino remain. The observation of neutrinoless double-beta decay could determine whether lepton number is violated, discover whether the neutrino is its own antiparticle, and provide information about the absolute scale of neutrino mass. The MAJORANA Collaboration will search for neutrinoless double-beta decay of germanium-76 in an array of germanium detectors. Previous experiments indicate that the half life of this decay mode is greater than 1025 years. To be sensitive to this rate, MAJORANA must construct an ultra-low-background detector. MAJORANA is building the DEMONSTRATOR, a 40-kg detector array, at the Sanford Underground Research Facility in Lead, South Dakota. The neutrinoless double-beta decay of 76-Ge would produce 76-Se and two electrons with 2039 keV of energy. The physics reach of the DEMONSTRATOR will be determined by the background count rate in a 4-keV energy region surrounding the 2039-keV Q-value. MAJORANA has a background goal of less than three counts in the energy region of interest per tonne-year of DEMONSTRATOR exposure. Projections of the DEMONSTRATOR's sensitivity are determined from a background energy-spectrum model based on material assay data and Monte Carlo simulation results. Understanding and minimization of backgrounds is critical to the success of the DEMONSTRATOR. MAJORANA Collaborators operate a low-background detector in a shielded environment at the Kimballton Underground Research Facility near Ripplemeade, Virginia. The contents of the detector cryostat are well known, making it a good candidate for testing the MAJORANA background model. This dissertation describes the creation of a background energy- spectrum model for the Kimballton detector. Energy spectra measured with the detector at Kimballton are compared to results of the background model, and implications for the DEMONSTRATOR are explored.
Author: Alexis G. Schubert Publisher: ISBN: Category : Languages : en Pages : 350
Book Description
The neutrino, an elementary particle, has been the subject of experimental investigation for over 50 years. Recent experiments have shown that neutrinos have mass and oscillate, but questions about fundamental properties of the neutrino remain. The observation of neutrinoless double-beta decay could determine whether lepton number is violated, discover whether the neutrino is its own antiparticle, and provide information about the absolute scale of neutrino mass. The MAJORANA Collaboration will search for neutrinoless double-beta decay of germanium-76 in an array of germanium detectors. Previous experiments indicate that the half life of this decay mode is greater than 1025 years. To be sensitive to this rate, MAJORANA must construct an ultra-low-background detector. MAJORANA is building the DEMONSTRATOR, a 40-kg detector array, at the Sanford Underground Research Facility in Lead, South Dakota. The neutrinoless double-beta decay of 76-Ge would produce 76-Se and two electrons with 2039 keV of energy. The physics reach of the DEMONSTRATOR will be determined by the background count rate in a 4-keV energy region surrounding the 2039-keV Q-value. MAJORANA has a background goal of less than three counts in the energy region of interest per tonne-year of DEMONSTRATOR exposure. Projections of the DEMONSTRATOR's sensitivity are determined from a background energy-spectrum model based on material assay data and Monte Carlo simulation results. Understanding and minimization of backgrounds is critical to the success of the DEMONSTRATOR. MAJORANA Collaborators operate a low-background detector in a shielded environment at the Kimballton Underground Research Facility near Ripplemeade, Virginia. The contents of the detector cryostat are well known, making it a good candidate for testing the MAJORANA background model. This dissertation describes the creation of a background energy- spectrum model for the Kimballton detector. Energy spectra measured with the detector at Kimballton are compared to results of the background model, and implications for the DEMONSTRATOR are explored.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Neutrino less double-beta (Ov beta beta) decay is a hypothesized process where in some even-even nuclei it might be possible for two neutrons to simultaneously decay into two protons and two electrons without emitting neutrinos. This is possible only if neutrinos are Majorana particles, i.e. fermions that are their own antiparticles. Neutrinos being Majorana particles would explicitly violate lepton number conservation, and might play a role in the matter-antimatter asymmetry in the universe. The observation of neutrinoless double-beta decay would also provide complementary information related to neutrino masses. The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, with a total of 40-kg Germanium detectors, to search for the Ov beta beta decay of Ge-76 and to demonstrate a background rate at or below 3 counts/ (ROI.t.y) in the 4 keV region of interest (ROT) around the 2039 keV Q-value for Ge-76 Ov beta beta decay. In this paper, we discuss the physics of neutrinoless double beta decay and then focus on the MAJORANA DEMONSTRATOR, including its design and approach to achieve ultra-low backgrounds and the status of the experiment.
Author: Hans Volker Klapdor-kleingrothaus Publisher: World Scientific ISBN: 9814470554 Category : Science Languages : en Pages : 1559
Book Description
In the last 20 years the disciplines of particle physics, astrophysics, nuclear physics and cosmology have grown together in an unprecedented way. A brilliant example is nuclear double beta decay, an extremely rare radioactive decay mode, which is one of the most exciting and important fields of research in particle physics at present and the flagship of non-accelerator particle physics.While already discussed in the 1930s, only in the 1980s was it understood that neutrinoless double beta decay can yield information on the Majorana mass of the neutrino, which has an impact on the structure of space-time. Today, double beta decay is indispensable for solving the problem of the neutrino mass spectrum and the structure of the neutrino mass matrix. The potential of double beta decay has also been extended such that it is now one of the most promising tools for probing beyond-the-standard-model particle physics, and gives access to energy scales beyond the potential of future accelerators.This book presents the breathtaking manner in which achievements in particle physics have been made from a nuclear physics process. Consisting of a 150-page highly factual overview of the field of double beta decay and a 1200-page collection of the most important original articles, the book outlines the development of double beta decay research — theoretical and experimental — from its humble beginnings until its most recent achievements, with its revolutionary consequences for the theory of particle physics. It further presents an outlook on the exciting future of the field.
Author: A. Morales Publisher: Elsevier ISBN: 1483257142 Category : Science Languages : en Pages : 539
Book Description
TAUP 91 covers the proceedings of the Second International Workshop on Theoretical and Phenomenological Aspects of Underground Physics, held in Toledo, Spain on September 9-13, 1991. The book focuses on the processes, methodologies, reactions, and transformations involved in underground physics. The selection first offers information on the fundamental issues in particle astrophysics and an overview of the problems related to general cosmology. Topics include connections between particle physics, astrophysics, and cosmology, stellar physics and particles, astrophysical ages, cosmic background radiation, and abundances of light elements. The text also takes a look at big bang nucleosynthesis constraints on new physics and microwave background radiation. The publication ponders on very wide band interferometric gravitational wave antenna and search for stellar gravitational collapse by macro. The text also examines high energy cosmic neutrinos of acceleration and non-acceleration origin; tests of general relativity and Newtonian gravity at large distances and the dark matter problem; and nuclear form factors for the scattering of neutralinos. The selection is a valuable reference for readers interested in underground physics.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Neutrinoless double beta decay searches play a major role in determining neutrino properties, in particular the Majorana or Dirac nature of the neutrino and the absolute scale of the neutrino mass. The consequences of these searches go beyond neutrino physics, with implications for Grand Unification and leptogenesis. The Majorana Collaboration is assembling a low-background array of high purity Germanium (HPGe) detectors to search for neutrinoless double-beta decay in 76Ge. The Majorana Demonstrator, which is currently being constructed and commissioned at the Sanford Underground Research Facility in Lead, South Dakota, will contain 44 kg (30 kg enriched in 76Ge) of HPGe detectors. Its primary goal is to demonstrate the scalability and background required for a tonne-scale Ge experiment. This is accomplished via a modular design and projected background of less than 3 cnts/tonne-yr in the region of interest. The experiment is currently taking data with the first of its enriched detectors.
Author: Julieta Gruszko Publisher: ISBN: Category : Languages : en Pages : 178
Book Description
Though the existence of neutrino oscillations proves that neutrinos must have non-zero mass, Beyond-the-Standard-Model physics is needed to explain the origins of that mass. One intriguing possibility is that neutrinos are Majorana particles, i.e., they are their own anti-particles. Such a mechanism could naturally explain the observed smallness of the neutrino masses, and would have consequences that go far beyond neutrino physics, with implications for Grand Unification and leptogenesis. If neutrinos are Majorana particles, they could undergo neutrinoless double-beta decay (0nBB), a hypothesized rare decay in which two antineutrinos annihilate one another. This process, if it exists, would be exceedingly rare, with a half-life over 1E25 years. Therefore, searching for it requires experiments with extremely low background rates. One promising technique in the search for 0nBB is the use of P-type point-contact (P-PC) high-purity Germanium (HPGe) detectors enriched in 76Ge, operated in large low-background arrays. This approach is used, with some key differences, by the MAJORANA and GERDA Collaborations. A problematic background in such large granular detector arrays is posed by alpha particles incident on the surfaces of the detectors, often caused by 222Rn contamination of parts or of the detectors themselves. In the MAJORANA DEMONSTRATOR, events have been observed that are consistent with energy-degraded alphas originating near the passivated surface of the detectors, leading to a potential background contribution in the region-of-interest for neutrinoless double-beta decay. However, it is also observed that when energy deposition occurs very close to the passivated surface, high charge trapping occurs along with subsequent slow charge re-release. This leads to both a reduced prompt signal and a measurable change in slope of the tail of a recorded pulse. Here we discuss the characteristics of these events and the development of a filter that can identify the occurrence of this delayed charge recovery (DCR) effect, allowing for the efficient rejection of passivated surface alpha events in analysis. Using a dedicated test-stand called the TUM Upside-down BEGe (TUBE) scanner, we have characterized the response of a P-PC detector like those used in the DEMONSTRATOR to alphas incident on the sensitive surfaces, developing a model for the radial dependence of the energy loss to charge trapping and determining the dominant mechanism behind the delayed charge effect. We have also used these measurements to demonstrate the complementarity of the DCR analysis with the drift-time analysis that is used to identify alpha background candidate events in the GERDA detectors. Using these two methods, we demonstrate the ability to effectively reject all alpha events (to within statistical uncertainty) with only 0.2% bulk event sacrifice. Applying the DCR analysis to the events observed in the MAJORANA DEMONSTRATOR, we find that it reduces the backgrounds in the 0nBB region-of-interest by a factor of 29, increasing the expected experimental sensitivity by a factor of 3 over the lifetime of the DEMONSTRATOR. The results of the dedicated measurements in the TUBE scanner can be used to build a background model for alpha decays in the DEMONSTRATOR; here, we examine two simplified geometric models for the alpha source distribution and find that the observed spectral shape is consistent with alpha events originating in the plastics of the detector units.
Author: Publisher: ISBN: Category : Languages : en Pages : 6
Book Description
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, 40-kg modular HPGe detector array to search for neutrinoless double beta decay in 76Ge. In view of the next generation of tonne-scale Ge-based 0[nu][beta][beta]-decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. The background rejection techniques to be applied to the data include cuts based on data reduction, pulse shape analysis, event coincidences, and time correlations. The Point Contact design of the DEMONSTRATOR's germanium detectors allows for significant reduction of gamma background.
Author: Alexis G. Schubert
Author: Alexis G. Schubert
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Author: Hans Volker Klapdor-kleingrothaus
Author: A. Morales![A Search for Double Beta Decay in [superscript]76 Ge PDF](https://books.google.com/books/content/images/frontcover/Y1RFQwAACAAJ?fife=w80-h100)
Author: Peter H. Fisher
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Author: Julieta Gruszko
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