Double-Cascade Events from New Physics in Icecube

A variety of new physics models allows for neutrinos to up-scatter into heavier states. If the incident neutrino is energetic enough, the heavy neutrino may travel some distance before decaying. In this work, we consider the atmospheric neutrino flux as a source of such events. At IceCube, this would lead to a “double-bang” (DB) event topology, similar to what is predicted to occur for tau neutrinos at ultrahigh energies. The DB event topology has an extremely low background rate from coincident atmospheric cascades, making this a distinctive signature of new physics. Our results indicate that IceCube should already be able to derive new competitive constraints on models with GeV-scale sterile neutrinos using existing data.

Figure 1

Schematic illustration of a DB event in IceCube. An incoming active neutrino $\nu$ up-scatters into a heavy neutrino $N$, which then propagates and decays into SM particles. The small circles represent the DOMs while the large circles indicate the positions where energy was deposited.

Figure 2

Expected potential of IceCube to constrain the mixing between ${\nu }_{\tau }$ and a heavy neutrino. In the region enclosed by the solid green contour, more than one DB event is expected during six years of data taking at IceCube. The dashed contour shows the most conservative result, where only the DeepCore volume is considered. The shaded regions are disfavored by CHARM [18] and DELPHI [17] at 90% and 95% C.L., respectively; see Ref. [14].

Figure 3

Expected potential to constrain magnetic moments leading to the transitions ${\nu }_{\tau }-N$ (left panel) and ${\nu }_{\mu }-N$ (right panel) at IceCube. In the region enclosed by the solid contours, at least one DB event would be expected at IceCube, for a data taking period of six years. The shaded regions are disfavored by previous experiments; see text for details.