Hints of New Physics from the KM3NeT and ANITA Anomalies with Dibya Chattopadhyay

About a year ago, the KM3NeT collaboration reported the observation of KM3-230213A, a neutrino event with an energy of 220 PeV. The absence of any $\mathcal{O}(100)$ PeV events in IceCube, despite its larger effective area and longer data-taking period, suggests an anomaly, with a tension quantified between approximately $ 2\sigma $ and $ 3.5 \sigma $, depending on the assumed source model. This implies a possible new physics origin for the event KM3-230213A. Meanwhile, the anomalous upgoing events detected by the ANITA experiment, with energies above 1 EeV and arrival angles implying traversal through at least a few hundred kilometers of Earth, similarly hint at a possible origin involving new physics in the neutrino sector.

We investigate new physics scenarios that could simultaneously account for both anomalies, particularly focusing on one in which a new matter potential induces a resonance in sterile-to-active neutrino transitions. Using the arc lengths traversed by the ANITA events, we identify the relevant parameter space and explore how matter-enhanced oscillations between the sterile and active sectors may help explain both the ANITA and KM3NeT observations. Overall, I will present the exciting possibility that recent ultra-high-energy neutrino observations have already observed physics beyond the Standard Model.

This lecture was made possible by the William C. Ferguson Fund.