Measurement of low-energy nuclear-recoil quenching factors in CsI[Na] and statistical analysis of the first observation of coherent, elastic neutrino-nucleus scattering Public Deposited

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  • March 20, 2019
Creator
  • Rich, Grayson
    • Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
Abstract
  • The COHERENT Collaboration has produced the first-ever observation, with a significance of \xsig{6.7}, of a process consistent with coherent, elastic neutrino-nucleus scattering (\cevns) as first predicted and described by D.Z. Freedman in 1974 \cite{freedman74}. Physics of the \cevns process are presented along with its relationship to future measurements in the arenas of nuclear physics, fundamental particle physics, and astroparticle physics, where the newly-observed interaction presents a viable tool for investigations into numerous outstanding questions about the nature of the universe. To enable the \cevns observation with a 14.6-kg \csi detector, new measurements of the response of \csi to low-energy nuclear recoils, which is the only mechanism by which \cevns is detectable, were carried out at Triangle Universities Nuclear Laboratory; these measurements are detailed and an effective nuclear-recoil quenching factor of $8.78 \pm 1.66 \%$ is established for \csi in the recoil-energy range of 5--30 keV, based on new and literature data. Following separate analyses of the \cevns-search data by groups at the University of Chicago and the Moscow Engineering and Physics Institute, information from simulations, calculations, and ancillary measurements were used to inform statistical analyses of the collected data. Based on input from the Chicago analysis, the number of \cevns events expected from the Standard Model is $173 \pm 48$; interpretation as a simple counting experiment finds $136 \pm 31$ \cevns counts in the data, while a two-dimensional, profile likelihood fit yields $134 \pm 22$ \cevns counts. Details of the simulations, calculations, and supporting measurements are discussed, in addition to the statistical procedures. Finally, potential improvements to the \csi-based \cevns measurement are presented along with future possibilities for COHERENT Collaboration, including new \cevns detectors and measurement of the neutrino-induced neutron spallation process.
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DOI
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Rights statement
  • In Copyright
Advisor
  • Henning, Reyco
  • Engel, Jonathan
  • Karwowski, Hugon
  • Barbeau, Phillip
  • Washburn, Sean
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017
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