Probing the Strength of Non-Standard Interactions Between Solar Neutrinos and Up or Down Quarks in Matter Using Recoil Electron Spectra Measured by Super-Kamiokande

Abstract

Non-Standard Interactions (NSI) between neutrinos and matter affect neutrino flavor oscillations.Due to the high matter density in the core of the Sun, solar neutrinos are well suited to probe these interactions.Using the 277 kton-yr exposure of Super-Kamiokande to $^{8}$B solar neutrinos, we search for the presence of NSI.Our data favors the presence of NSI with down quarks at 1.8$\sigma$, and with up quarks at 1.6$\sigma$, with the best-fit effective NSI parameters being ($\epsilon_{11}^{\textrm{d}},\epsilon_{12}^{\textrm{d}}$) = (-3.3, -3.1) for d-quarks and ($\epsilon_{11}^{\textrm{u}},\epsilon_{12}^{\textrm{u}}$) = (-2.5, -3.1) for u-quarks.After combining with data from the Sudbury Neutrino Observatory and Borexino, the significance increases by 0.1$\sigma$