A Measurement of Solar Neutrinos and the Development of Reconstruction Algorithms for the SNO+ Experiment

• Author / Creator

  Jie Hu

• This thesis presents a measurement of the flux of Boron-8 ($^8$B) solar neutrinos. The measurement is based on a dataset of 190.33 live days acquired during the SNO+ water physics commissioning. To analyze the data, an event reconstruction framework was developed to evaluate the orientation of the incoming neutrino's momentum vector and the position of the event it induces. A multivariate analysis was applied to reduce the number of background events in the analysis dataset. By analyzing the data within an energy range from 5 to 15 MeV, an observed elastic scattering flux assuming no neutrino flavor transformation is obtained as $\Phi{\mathrm{ES}}=(2.10 \pm 0.204 \mathrm{(stat.)}^{+0.169}{-0.0722}\mathrm{(syst.)})\times10^6$ cm$^{-2}$s$^{-1}$ while the total $^8$B solar neutrino flux is evaluated as $\Phi{\mathrm{^8B}}=(4.62 \pm 0.447 \mathrm{(stat.)}^{+0.300}{-0.137}\mathrm{(syst.)})\times10^6$ cm$^{-2}$s$^{-1}$. These fluxes are consistent with the previous measurement published by SNO+ [Anderson, M., et al. Measurement of the $^8$B Solar Neutrino Flux in SNO+ with Very Low Backgrounds.'' Physical Review D 99.1 (2019): 012012], and the measurements from Super Kamiokande [Abe, K., et al.Solar Neutrino Measurements in Super-Kamiokande-IV.'' Physical Review D 94.5 (2016): 052010] and Borexino [Agostini, M., et al. ``Improved measurement of 8B solar
  neutrinos with 1.5 kt$\cdot$y of Borexino exposure.'' Physical Review D 101.6 (2020): 062001]. The systematics were obtained by reconstructing and analyzing the calibration datasets from a nitrogen-16 calibration source.

  Currently, the SNO+ experiment has completed the water phase commission and is filled with the liquid scintillator. It turns from a water Cherenkov detector into a 780-tonne liquid scintillator detector. Tellurium-130 isotopes will be loaded into the detector to fulfill the ultimate physics goal of SNO+: to search for the neutrinoless double beta decay. The other parts of this thesis discuss the reconstruction framework for the partial-fill and scintillator phases. For the scintillator phase, the event reconstruction gives a high position resolution down to about 65 mm.

• Subjects / Keywords

  • SNO+ solar neutrino reconstruction particle physics

• Graduation date

  Spring 2022

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-xgqf-tt05

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.