Constraints on Flavor-Diagonal Non-Standard Neutrino Interactions from Borexino Phase-II

Understand

The Borexino detector measures solar neutrino fluxes via neutrino-electron elastic scattering.

• Observed spectra are determined by the solar-$\nu_{e}$ survival probability $P_{ee}(E)$, and the chiral couplings of the neutrino and electron.
• Some theories of physics beyond the Standard Model postulate the existence of Non-Standard Interactions (NSI's) which modify the chiral couplings and $P_{ee}(E)$.
• In this paper, we search for such NSI's, in particular, flavor-diagonal neutral current interactions that modify the $\nu_e e$ and $\nu_\tau e$ couplings using Borexino Phase II data.