Constraints on non-standard neutrino interactions from Borexino extended data-set

TL;DR

This paper uses Borexino's extended data to set new, more stringent limits on non-standard neutrino interactions, including for the first time a comprehensive analysis of all off-diagonal NSI parameters, advancing the search for new physics.

Contribution

It provides an updated and more comprehensive analysis of flavor-diagonal and off-diagonal NSI parameters using Borexino Phase-III data, surpassing previous constraints and exploring the full NSI parameter space.

Findings

Improved constraints on diagonal NSI parameters.

First comprehensive analysis of all off-diagonal NSI terms.

Enhanced sensitivity compared to Phase-II results.

Abstract

Neutrino non-standard interactions (NSI) constitute an active research field, as they are closely related to potential new physics associated with dark matter searches and exotic interactions arising from fundamental symmetry violations. The Borexino's unprecedented sensitivity to solar neutrinos, derived from its low background and precision spectral measurements, enables stringent constraints on potential deviations from the standard three-flavor neutrino oscillation paradigm. This work presents an update on the analysis of flavor-diagonal NSI using the full Borexino Phase-III data set, extending the study previously reported in Constraints on flavor-diagonal non-standard neutrino interactions from Borexino Phase-II (JHEP 2020, 38). The updated analysis incorporates the extended temporal and statistical coverage of Phase-III. The results indicate improved sensitivity to the diagonal NSI parameters, with constraints exceeding those obtained in Phase-II. Furthermore, a more general analysis that includes all possible off-diagonal NSI terms is presented for the first time, providing a comprehensive exploration of the NSI parameter space associated with the flavors of the incoming and outgoing neutrinos. This work once again underlines Borexino's critical role in probing new physics scenarios and reinforces its legacy in neutrino research. Detailed comparisons with Phase-II results are discussed, along with implications for theoretical models of NSI.