Constraining the HEP solar neutrino and diffuse supernova neutrino background fluxes with the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory has demonstrated that the apparent deficit in solar neutrinos observed on Earth is due to matter-enhanced flavor transitions, and provided precision measurements of the relevant oscillation parameters. The low backgrounds and large, spectral charged-current $\nu_e-d$ cross section that enabled these measurements also give SNO unique sensitivity to two yet-unobserved neutrino signals of great interest: the $hep$ solar neutrino flux and the diffuse supernova neutrino background (DSNB). This work presents a joint analysis of all three running configurations of the SNO experiment in order to improve constraints on the $hep$ and DSNB $\nu_e$ fluxes. The crucial uncertainties in the energy response and atmospheric neutrino background, as well as the event selection criteria, are reevaluated. Two analysis approaches are taken, a single-bin counting analysis ($hep$ and DSNB) and multidimensional signal extraction fit ($hep$), using a random sample representing 1/3 of the total SNO data. These searches are the most sensitive to date for these important signals, and will improve further when the full dataset is analyzed. The SNO+ liquid scintillator experiment is a successor to SNO primarily concerned with a search for neutrinoless double-beta decay ($0\nu\beta\beta$) in $^{130}$Te. The modifications to the SNO detector in preparation for SNO+ and an analysis of the $0\nu\beta\beta$ sensitivity of this upcoming experiment will also be presented in this work. SNO+ will be the first experiment to load Te into liquid scintillator, and is expected to achieve world-class sensitivity in an initial phase commencing in 2017, with significantly improved sensitivity in an upgraded configuration to follow using much higher Te target mass. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Physics & Astronomy First Advisor Joshua R. Klein Subject Categories Physics This dissertation is available at ScholarlyCommons: http://repository.upenn. edu/edissertations/1884 CONSTRAINING THE HEP SOLAR NEUTRINO AND DIFFUSE SUPERNOVA NEUTRINO BACKGROUND FLUXES WITH THE SUDBURY NEUTRINO OBSERVATORY Andrew T. Mastbaum A DISSERTATION in Physics and Astronomy Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2016 Supervisor of Dissertation Graduate Group Chairperson Joshua R. Klein Ravi Sheth Professor of Physics Professor of Physics Dissertation Committee: Evelyn Thomson, Associate Professor of Physics Eugene Beier, Professor of Physics Masao Sako, Associate Professor of Physics Adam Lidz, Associate Professor of Physics CONSTRAINING THE HEP SOLAR NEUTRINO AND DIFFUSE SUPERNOVA NEUTRINO BACKGROUND FLUXES WITH THE SUDBURY NEUTRINO OBSERVATORY COPYRIGHT c © 2016 Andrew T. Mastbaum This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/4.0/ “In cosmological neutrino physics, no neutrinos are harmed. In neutrino astrophysics individual neutrinos must be captured and killed so that we can learn more. ” — John Beacom, APS April Meeting 2015 This dissertation is dedicated to all the neutrinos who sacrificed everything in the name of scientific progress. Seriously, though, it’s for Lauren.