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

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.

Figure 1

The mass spectrum of our model. The left box displays the heavy PeV-scale states as well as the TeV-scale Higgsinos. The right box shows the active and sterile neutrino mass eigenstates. Particles that form some fraction of dark matter are denoted by dashed blue lines.

Figure 2

The expected number of neutrino events at IceCube from the decay of $X$ (blue), together with IceCube data points and error bars (black) and atmospheric background (green) from Ref. [1], and the total number of $\text{signal}+\text{background}$ events (red).