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| Home > Publications database > Solar neutrino detection: CNO discovery with Borexino and preparations for success in JUNO and OSIRIS |
| Home > Publications database > Solar neutrino detection: CNO discovery with Borexino and preparations for success in JUNO and OSIRIS |
| Dissertation / PhD Thesis | FZJ-2023-01554 |
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2022
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Please use a persistent id in citations: http://hdl.handle.net/2128/34200 doi:10.18154/RWTH-2023-00596
Abstract: The Sun is powered through different fusion processes that can be grouped in two major categories: the pp-chain and the CNO cycle. Building a theory of the balance between gravitational and radiation forces is difficult, not least because almost all of the information about the Sun can only be gathered at a surface level. Particle physics however predicts that the two aforementioned processes emit different kinds of neutrinos: solar neutrinos. While their elusive nature makes them extremely difficult to detect, the same property allows them to escape from the solar core. They are the only direct probe of the solar interior and their measurement on Earth represents a tremendous experimental and theoretical success. In this thesis, methods related to the experimental challenges of measuring CNO neutrinos are being explored. These neutrinos constitute less than one percent of the Sun’s neutrino output but their generating process is thought to be the main source of stellar energy in our universe. The findings in this thesis led in part to the first experimental evidence for CNO neutrinos with the Borexino detector, which was published in Nature. Another part of this thesis focuses on JUNO’s expected sensitivity to solar neutrinos. JUNO is a very large liquid scintillator currently under construction in south China and is shown in this thesis to have the potential for unprecedentedly precise solar neutrino measurements. These sensitivity studies are also currently under preparation for publication. Finally, this thesis encompasses work with the OSIRIS detector, a pre-detector for JUNO which will make sure its liquid scintillator doesn’t exceed certain levels of contamination - which could dismantle its sensitivity not only to its main goal of measuring the neutrino mass hierarchy with 3σ in six years, but also severely hinder its solar neutrino measurements. The first part of this section is about developing a source calibration program which will perform all of OSIRIS’s calibration needs: energy reconstruction, vertex reconstruction, charge reconstruction, inter-PMT time offsets on a sub-nano-second scale, and charge dependence of PMT responses. It will also be used to monitor OSIRIS’s scintillator for time-dependent changes thus providing fast feedback. The results presented in this thesis are also currently being implemented in a paper which is planned to be published once the first calibration data has been measured, which will probably be at the end of the year. In the second part of this section, OSIRIS’s sensitivity to its main goal of measuring $^{238}$U and $^{232}$Th in the liquid scintillator is calculated with an improved analysis compared to existing ones. The results on OSIRIS’s sensitivity to its main goal and to $^{85}$Kr were already published in the European Physical Journal C as part of an overall design and sensitivity review.
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