An algorithm for detecting quantum gravity photon dispersion in gamma-ray bursts: DisCan

DisCan is a new algorithm implementing photon dispersion cancellation in order to measure energy-dependent delays in variable sources. This method finds the amount of reversed dispersion that optimally cancels any actual dispersion present. It applies to any time- and energy-tagged photon data and avoids binning in both time and energy. The primary motivation here is the search for quantum gravity-based dispersion in future gamma-ray burst data from the Gamma-Ray Large Area Space Telescope ( GLAST). Extrapolation of what is known about bursts at lower energies yields a reasonable prospect that photon dispersion effects consistent with some quantum gravity formalisms may be detected in sufficiently bright bursts. Short bursts have no or very small inherent lags and are therefore better prospects than long ones, but even they suffer a systematic error due to pulse asymmetry that may yield an irreducible uncertainty. We note that observations at TeV energies and higher will be useful for detecting dispersion in GRBs, using this and other algorithms, only if energy resolution can be improved over what is currently achieved.