Luminous solar neutrinos I: Dipole portals

TL;DR

This paper investigates how solar neutrinos interacting within the Earth can produce detectable signals via a dipole portal, revealing new parameter space constraints and potential for future detection methods.

Contribution

It introduces the study of a neutrino dipole portal with decay length considerations, analyzing Borexino data to explore previously untested parameter space in the 0.5--20 MeV range.

Findings

Borexino data constrains new neutrino dipole interactions.

Decay length independence when decay occurs inside Earth.

Complementary to cosmological and supernova bounds.

Abstract

Solar neutrinos upscattering inside the Earth can source unstable particles that can decay inside terrestrial detectors. Contrary to naive expectations we show that when the decay length is much shorter than the radius of the \emph{Earth} (rather than the detector), the event rate is independent of the decay length. In this paper we study a transition dipole operator (neutrino dipole portal) and show that Borexino's existing data probes previously untouched parameter space in the 0.5--20 MeV regime, complementing recent cosmological and supernova bounds. We briefly comment on similarities and differences with luminous dark matter and comment on future prospects for analogous signals stemming from atmospheric neutrinos.