Lorentz-Violating Scenarios for the Highest-Energy Photons from GRB 221009A.

A photon at E≃251  TeV from GRB 221009A was detected by the Carpet Collaboration in 2022 using a partial dataset. Very recently, Carpet has completed its full data analysis reporting further support for its previous photon now at E=300_{-38}^{+43}  TeV. Within standard propagation models, this observation is in strong tension with conventional expectations since such a photon is absorbed by the CMB. Further, we show that this detection is strongly disfavored within the explored scenarios involving axionlike particles (ALPs) alone. Instead, we find that the considered photon is compatible with specific Lorentz invariant violation (LIV) frameworks with the LIV scale obeying in the linear case E_{LIV,1}<1.22_{-0.22}^{+0.19}×10^{21}  GeV at 95% CL and in the quadratic case E_{LIV,2}<2.03_{-0.22}^{+0.17}×10^{13}  GeV at 95% CL. Finally, we outline scenarios where standard photon-ALP oscillations are combined with LIV-induced modifications of photon propagation, which provide a consistent interpretation of the observations of GRB 221009A concerning the highest-energy photons detected by the LHAASO and the Carpet Collaborations.