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This Is Just the Beginning: The Hunt for Astrophysical Neutrinos

Li, Weishi
http://rave.ohiolink.edu/etdc/view?acc_num=osu1500327728838636

Abstract Details

2017, Doctor of Philosophy, Ohio State University, Physics.
Astrophysical neutrinos are precious messengers of our Universe. They reveal information about the core of the Sun, the interiors of exploding stars, the sites of cosmic-ray acceleration, and fundamental properties of neutrinos. Yet, the study of astrophysical neutrinos has been a difficult quest. Because neutrinos interact only weakly with matter, we need kilo-ton-scale or even larger detectors to detect reasonable numbers of signal events. Modest numbers of signal events are overwhelmed by large numbers of background events, i.e., events that look like neutrinos but they are caused by other processes. On top of that, we are limited in what neutrino properties we can extract from detected events, and with what precision. In this dissertation, I discuss a series of papers aimed at improving our measurements of astrophysical neutrinos. Solar neutrinos, with energies around 10 MeV, have been detected in Super-Kamiokande for 20 years, yet some key measurement results are still inconclusive. One limiting factor is the spallation background induced by cosmic-ray muons. To better reject this background, I first calculate the spallation yields in Super-Kamiokande. I then study the production mechanisms of spallation backgrounds in detail and conclude that they depend on muon-induced electromagnetic and hadronic showers, rather than by muons themselves. Next, I explore how to reconstruct showers in Super-Kamiokande with high fidelity and propose a new spallation cut utilizing better-reconstructed shower profiles. On the TeV -- PeV astrophysical neutrino front, one experimental limitation with current detection techniques is that they cannot distinguish between two neutrino types, or flavors, $\nu_e$ and $\nu_\tau$. To solve this problem, I propose two new shower-related experimental observables, muon echoes and neutron echoes, that are stronger in $\nu_\tau$-initiated events. The methods presented in this dissertation have been adopted by neutrino experimental collaborations, with results yet to come out. This is just the beginning.
John Beacom (Advisor)
168 p.
Astrophysics; Physics

Recommended Citations

Citations

  • Li, W. (2017). This Is Just the Beginning: The Hunt for Astrophysical Neutrinos [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500327728838636

    APA Style (7th edition)

  • Li, Weishi. This Is Just the Beginning: The Hunt for Astrophysical Neutrinos. 2017. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1500327728838636.

    MLA Style (8th edition)

  • Li, Weishi. "This Is Just the Beginning: The Hunt for Astrophysical Neutrinos." Doctoral dissertation, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1500327728838636

    Chicago Manual of Style (17th edition)

osu1500327728838636
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© 2017, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.