Hints of New Physics from the KM3NeT and ANITA Anomalies

by Dibya Sankar Chattopadhyay (Oklahoma State University)

Thursday 28 Aug 2025, 13:30 → 14:30 Europe/Zurich

4/2-037 - TH meeting room (CERN)

The KM3NeT collaboration recently reported the observation of KM3-230213A, a neutrino event with an energy of 220 PeV. The absence of any 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 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.