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| Current Research and Future Direction |
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Neutrinos and Neutrino Oscillations. Beginning in the 1960's, it became clear that our understanding of incident radiation from the sun was incomplete. The incoming flux of neutrinos (elementary, nearly massless particles originally observed in the context of nuclear beta-decay) was approximately one third of the value predicted by theoretical models of the sun's core, a quandary known as the “solar neutrino problem”. Further study has engendered massive international research efforts devoted entirely to these tiny particles. Because neutrinos interact only via the weak force, their behavior is unaffected by electro-magnetic interactions and, if they are truly massless, by the gravitational force as well. This makes them ideal probes of the nucleus, able to provide us with detailed information about nucleon structure. In addition, neutrinos have been observed to oscillate from one variety, or flavor, to another and it is this observation that ultimately led to and explanation of the solar neutrino problem. Neutrinos' oscillatory behavior is currently the subject of intense study to determine the neutrino mass and the extent to which neutrino flavors intermix resulting in “appearances” and “disappearances” along their paths of flight.
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Cosmology and Cosmic Strings. I am also involved in collaborative work focusing on the search for cosmic strings using publicly available Great Observatories Origins Deep Sky Survey (GOODS) data. With the GOODS set, which includes data from the Hubble Space Telescope and Chandra X-ray Observatory, we are investigating paired galaxies and their implications for the existence of cosmic strings. Cosmic strings are theorized to be string-like clumps of energy created during the expansion of the universe subsequent to the “Big Bang” and which are unrelated to other forms of large scale structure such as galaxy filaments and superclusters. Such a string, located between the earth and distant stellar objects (stars and galaxies) along our line of sight would, through gravitational lensing, produce “double images” of those objects observable, in principle, within the GOODS field of view. Cosmic strings have not yet been unequivocally observed and may be the oldest relics in the universe. Indications of their existence would be important confirmation of particle physics models of the first seconds of the Big Bang and their energy density would constrain models of inflation. Discovery of cosmic strings will lead to a vast range of research opportunities.
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T. Araki et al. (The KamLAND Collaboration), “Experimental Investigation of geologically produced antineutrinos with KamLAND”, Phys. Rev. Lett. 94:081801,2005.
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T. Araki et al. (The KamLAND Collaboration), “Measurement of Neutrino Oscillation with KamLAND: Evidence of Spectral Distortion”, Phys. Rev. Lett. 94:081801,2005.
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K. Eguchi et al. (The KamLAND Collaboration), “First Results from KamLAND: Evidence for Reactor Anti-Neutrino Disappearance”, Phys. Rev. Lett. 90, 021802, 2003.
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G.P. Zeller et al. (The NuTeV Collaboration), “A Precise Determination Of Electroweak Parameters In Neutrino Nucleon Scattering”, Phys. Rev. Lett. 88, 091802, 2002.
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