Is There New Physics Beyond 30 TeV in the BOAT?

TL;DR

This work probes Lorentz Invariance Violation (LIV) in the photon sector using a quadratic subluminal framework to predict anomalous transparency in high-energy photon-photon interactions. It adopts the complete LIV-modified cross section for gamma-gamma to e- e+ from Carmona 2024 and computes the observed flux with attenuation τ(E,z_s) determined by integrating over the EBL and CMB backgrounds. Focusing on GRB 221009A as measured by LHAASO, it extrapolates the intrinsic spectrum to ~100 TeV and identifies potential LIV-induced flux recovery above ~30 TeV; the key thresholds are $2 E epsilon (1 - cos theta) - E^4/Lambda^2 ≥ 4 m_e^2$ and $E ≤ [2 epsilon (1 - cos theta) Lambda^2]^{1/3}$, with a SED maximum scaling $E^* ∝ Lambda^{2/3}$ and a diagnostic fit $E^* = 3.3×10^{-5} Lambda^{2/3} + 17.8 TeV$. The results imply that LIV could enhance detectability if the intrinsic spectrum extends beyond 30 TeV, but no LHAASO data in these bins currently constrain Lambda; the work motivates targeted analyses and underscores SWGO's role in LIV searches for AGN.

Abstract

We show that the GRB 221009A spectrum detected by LHAASO can be used to probe effects of quadratic subluminal Lorentz Invariance Violation (LIV) through the enhancement of the observed flux at the highest energies. In particular, we argue that excesses in the GRB 221009A data currently classified as non-detections at energies $E \gtrsim 30$ TeV warrant further investigation, as they may indicate a recovery of the intrinsic source spectrum consistent with the LIV-induced suppression of $γγ\to e^-e^+$ interactions within the quadratic subluminal scenario. This would increase the accessible parameter space of the energy scale of new physics.

Figures (3)

• Figure 1: Intrinsic average data points of GRB 221009A (colored markers) for five time intervals between 14 and 1774 s after the trigger burst, extracted from the supplementary material of LHAASO:2023kyg, together with the corresponding intrinsic spectrum (\ref{['eq:int']}) obtained from the time-averaged fit Miceli:2024yhv normalized to the BOAT highest state, corresponding to the first 14 s (upper brown plus-filled markers). The dashed light-blue curves represent spectra modified by LIV effects for six $\Lambda$ values, using the $\gamma\gamma \rightarrow e^{-}e^{+}$ modified cross section from Carmona:2024thn. The green curves indicate the LHAASO sensitivity scaled to observation times of 1 hour, and 1 minute.
• Figure 2: Relation between the LIV SED peak energy $E^{*}$ and the corresponding energy scale $\Lambda$ for the six cases in consideration. We find that $E^*$ follows the dependence on $\Lambda$ as the second energy threshold, namely $\Lambda^{2/3}$.
• Figure 3: LIV observational prospect for the blazar PKS 2155-304 in the subluminal quadratic scenario. The red solid line shows the intrinsic spectrum taken from 4FGL catalogue modeled as LP, meanwhile the red dashed line shows the 4FGL spectrum with exponential cut-off where $E_{cut}=10$ TeV. The blue solid line shows EBL+CMB absorbed spectrum in SR scenario, while dashed light-blue curves show absorbed spectrum assuming different scales of LIV. The green curves (circles) are the SWGO sensitivities (estimated sensitivity extension) for 1 and 5 years of time observation taken from SWGO:2025taj.