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

Abstract

A photon at $\mathcal{E}\simeq 251\mathrm{TeV}$ 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 $\mathcal{E}=300_{-38}^{+43}\mathrm{TeV}$. 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 ${\mathcal{E}}_{\mathrm{LIV},1}<1.22_{-0.22}^{+0.19}\times 10^{21}\mathrm{GeV}$ at $95\%$ CL and in the quadratic case ${\mathcal{E}}_{\mathrm{LIV},2}<2.03_{-0.22}^{+0.17}\times 10^{13}\mathrm{GeV}$ 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.

Comments: Accepted for publication in Physical Review Letters. 26 pages, 10 figures. Includes Supplemental Material