PeV neutrinos and a 3.5 keV x-ray line from a PeV-scale supersymmetric neutrino sector

Abstract

Recent measurements of PeV energy neutrinos at IceCube and a 3.5 keV x-ray line in the spectra of several galaxies are both tantalizing signatures of new physics. This paper shows that one or both of these observations can be explained within an extended supersymmetric neutrino sector. Obtaining light active neutrino masses as well as phenomenologically interesting (keV--GeV) sterile neutrino masses without any unnaturally small parameters hints at a new symmetry in the neutrino sector that is broken at the PeV scale, presumably tied to supersymmetry breaking. The same symmetry and structure can sufficiently stabilize an additional PeV particle, produce its abundance through the freeze-in mechanism, and lead to decays that can give the energetic neutrinos observed by IceCube. The lightest sterile neutrino, if at 7 keV, is a nonresonantly produced fraction of dark matter, and can account for the 3.5 keV x-ray line. The two signals could therefore be the first probes of an extended supersymmetric neutrino sector.