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

Abstract

A photon at ${\cal E} \simeq 251 \, \rm TeV$ from GRB 221009A was detected by the Carpet collaboration in 2022 using a partial data set. Very recently, Carpet has completed its full data analysis reporting further support for its previous photon now at ${\cal E} = 300^{+ 43}_{- 38} \, {\rm TeV}$. 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 axion-like 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 ${\cal E}_{{\rm LIV}, 1} < 1.22_{-0.22}^{+0.19} \times 10^{21} \, {\rm GeV}$ at $95 \%$ CL and in the quadratic case ${\cal E}_{{\rm LIV}, 2} < 2.03_{-0.22}^{+0.17} \times 10^{13} \, {\rm GeV}$ 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 including the highest energy photons detected by the LHAASO and Carpet collaborations.