Speaker
Description
The brightest cosmic gamma-ray burst (GRB) ever detected, GRB~221009A, was accompanied by photons of very high energies. These gamma rays may be used to test both the astrophysical models of the burst and our understanding of long-distance propagation of energetic photons, including potential new-physics effects. Here we present the observation of a photon-like air shower with the estimated primary energy of $300^{+43}_{-38}$ TeV, coincident (with the chance probability of $\sim 9\cdot 10^{-3}$) with the GRB in its arrival direction and time. Making use of the upgraded Carpet-3 muon detector and new machine learning analysis, we estimate the probability that the primary was hadronic as $\sim 3 \cdot 10^{-4}$. This is the highest-energy event possibly associated with any GRB.
