Speaker
Description
Speaker: Dibya Sankar Chattopadhyay
Abstract: The ANITA-IV experiment has reported four anomalous upgoing neutrino-candidate events with energies above 1 EeV and arrival directions implying propagation through at least several hundred kilometers of Earth. More recently, the KM3NeT Collaboration reported KM3-230213A, an exceptionally energetic event consistent with a parent neutrino in the (0.1-1) EeV range. The absence of comparable events in IceCube is particularly intriguing, given IceCube’s substantially larger total exposure. In this talk, I first quantify this discrepancy within Standard-Model-like interpretations under both diffuse all-sky and transient-source scenarios. For a diffuse Standard Model interpretation, I show that the ANITA-IV events would correspond to an upward fluctuation of ~7. I then quantify the tension for rare transient populations distributed uniformly across the sky over IceCube’s ~15 year runtime. Finally, I discuss whether beyond-the-Standard-Model modifications involving sterile-to-active neutrino conversions that are enhanced in the presence of matter effects can alleviate this tension, and place the ANITA-IV vs. IceCube anomaly in the broader context of the recent ultra-high-energy event reported by KM3NeT.