A Portalino to the Dark Sector

TL;DR

This paper introduces a simplified dark sector model featuring a 'portalino' that couples standard model neutrinos to dark matter, evading many constraints and offering unique collider and astrophysical signatures.

Contribution

It proposes a novel 'portalino' mechanism linking neutrinos and dark matter, simplifying dark sector interactions and predicting new experimental signals.

Findings

Dark matter can freeze out into neutrinos, avoiding CMB constraints.

The portalino predicts small deviations in neutrino couplings and collider signatures.

Potential astrophysical signals include monochromatic neutrinos and spectral features in cosmic rays.

Abstract

"Portal" models that connect the Standard Model to a Dark Sector allow for a wide variety of scenarios beyond the simplest WIMP models. Kinetic mixing of gauge fields in particular has allowed a broad range of new ideas. However, the models that evade CMB constraints are often non-generic, with new mass scales and operators to split states and suppress indirect detection signals. Models with a "portalino", a neutral fermion that marries a linear combination of a standard model neutrino and dark sector fermion and carries a conserved quantum number, can be simpler. This is especially interesting for interacting dark sectors; then the unmarried linear combination which we identify as the standard model neutrino inherits these interactions too, and provides a new, effective interaction between the dark sector and the standard model. These interactions can be simple $Z'$ type interactions or lepton-flavor changing. Dark matter freezes out into neutrinos, thereby evading CMB constraints, and conventional direct detection signals are largely absent. The model offers different signals, however. The "portalino" mechanism itself predicts small corrections to the standard model neutrino couplings as well as the possibility of discovering the portalino particle in collider experiments. Possible cosmological and astroparticle signatures include monochromatic neutrino signals from annihilation, spectral features in high energy CR neutrinos as well as conventional signals of additional light species and dark matter interactions.