Speaker
Description
Flares produced by some classes of astrophysical objects may be sources of some ultra-high-energy particles, which, if they are neutral, would group into clusters, highly correlated in space and time. Identification of such clustering in cosmic-ray data would provide important evidence for possible existence of neutral particles of ultra-high-energies (UHE) and could potentially help identify their sources. We present an analysis method to search for space-time clustering of ultra-high-energy extensive air showers, namely the stacking method, which uses a time-clustering algorithm combined with an unbinned likelihood study. In addition, to enhance the capability to discriminate between signal (specifically photon-initiated events) and background (hadron-initiated) events, we apply a photon tag. This involves using relevant probability distribution functions to classify each event as more likely to be either a photon or a hadron. We demonstrate that the stacking method is able to effectively distinguish between events initiated by photons and those initiated by hadrons (background). The number of photon events in a data sample, as well as the flare/flares duration can also be retrieved correctly. The stacking method with a photon tag requires only a few events to identify a photon flare. This method can be used to search for the cosmic ray sources and/or improve limits on the fluxes of UHE photons.
