Browsing by Subject "Neutrinos--Mass"
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Item Inferencing neutrino mass hierarchy from cosmology(2011-05) Leu, Richard Hsueh-Yee; Dicus, Duane A.; Bohm, Arno; Chiu, Charles; Komatsu, Eiichiro; Sitz, GregThe observation of solar and atmospheric neutrino oscillations place bounds on the mass differences. However, these probes are insensitive to the absolute mass. To date, cosmology has provided the best bounds on the total neutrino mass. These bounds are based on a degenerate mass model. With the increasing precision of cosmological data, we investigate the effect of the neutrino mass hierarchy. The precision of the parameter estimates stems from precise observations of the cosmic microwave background. However, the effect of neutrino mass hierarchy on this observation is smaller than the cosmic variance. Therefore, we rely on the measurement of the matter power spectrum for hierarchy effects. We propose the use of importance sampling rather than the commonly used Markov chain Monte Carlo. Importance sampling takes advantage of the microwave background's statistical insensitivity to hierarchy. We present forecasted bounds due to Planck and the proposed CMBPol. We also discuss the needed precision for future galaxy surveys in detecting the effect of neutrino mass hierarchy.Item The tritium recycling system for the Neutrino Mass Experiment at Texas (NEXTEX)(2004-12-18) Eckart, Michael; Fink, Manfred, 1937-For decades people have tried to measure the rest masses of the neutrinos, but this quest has not yet been successful. The most commonly used method to determine the rest mass of the electron anti-neutrino is to measure the high energy end of the tritium beta decay spectrum. Various experiments suffered from conceptional problems, so that currently only an upper limit of 2.3 eV is known for the rest mass of the electron anti-neutrino. The Neutrino Experiment at the University of Texas (NEXTEX) has been thoroughly designed to avoid many problems that have been encountered in former attempts to measure the rest mass. The goal of NEXTEX is to lower the upper limit to less than 0.8 eV and by doing so possibly measure the rest mass of the electron anti-neutrino for the first time. The tritium recycling system is an important part of this experiment and the purpose of this thesis is not only to describe this recycling system in detail, but also to provide information about various potential problems that might arise and how they have been solved. These potential problems include catalysts, unwanted surface reactions and the solubility of tritium in Fomblin. The latter has just recently been investigated and a great deal of attention will therefore be dedicated to the presentation of the latest results.