Identify the source of the KM3-230213A ultra-high-energy neutrino

Identify the astrophysical source of the ultra-high-energy neutrino event KM3-230213A detected by the KM3NeT ARCA array, including the counterpart class and sky location, to ascertain the propagation distance and refine constraints on the Lorentz-invariance-violating superluminal neutrino velocity parameter δ.

Background

KM3-230213A is reported as the highest-energy neutrino detected to date, with an estimated energy of 220^{+570}_{-110} PeV. The analysis uses this event to set a stringent upper limit on the Lorentz-invariance-violating parameter δ, which characterizes potential superluminal neutrino propagation via electron-positron pair emission.

The constraint on δ depends on the neutrino’s energy and propagation distance. While the event’s energy is estimated, the source (and thus the exact distance) remains unidentified. The authors conservatively assume galactic or intergalactic baselines to derive limits, noting that identifying the source would solidify the baseline and enable more precise constraints.