Search for Lorentz Invariance breaking with a likelihood fit of the PKS 2155-304 flare data taken on MJD 53944

TL;DR

This study uses a likelihood fit method on PKS 2155-304 flare data to set new constraints on Lorentz Invariance breaking, improving previous limits and providing the best results with blazars and AGN.

Contribution

It introduces a more sensitive likelihood fit approach to analyze gamma-ray data for Lorentz symmetry breaking constraints.

Findings

Linear term limit improved by a factor of ~3 to M^{l}_{QG} > 2.1x10^{18} GeV

Quadratic term limit set at M^{q}_{QG} > 6.4x10^{10} GeV

Achieved the best limits with blazars and AGN to date.

Abstract

Several models of Quantum Gravity predict Lorentz Symmetry breaking at energy scales approaching the Planck scale (10^{19} GeV). With present photon data from the observations of distant astrophysical sources, it is possible to constrain the Lorentz Symmetry breaking linear term in the standard photon dispersion relations. Gamma-ray Bursts (GRB) and flaring Active Galactic Nuclei (AGN) are complementary to each other for this purpose, since they are observed at different distances in different energy ranges and with different levels of variability. Following a previous publication of the High Energy Stereoscopic System (H.E.S.S.) collaboration, a more sensitive event-by-event method consisting of a likelihood fit is applied to PKS 2155-304 flare data of MJD 53944 (July 28, 2006) as used in the previous publication. The previous limit on the linear term is improved by a factor of ~3 up to M^{l}_{QG} > 2.1x10^{18} GeV and is currently the best result obtained with blazars. The sensitivity to the quadratic term is lower and provides a limit of M^{q}_{QG} > 6.4x10^10 GeV, which is the best value obtained so far with an AGN and similar to the best limits obtained with GRB.