Multiple UHECR Events from Galactic hadron jets

We propose a new observational test of top-down source models for the ultra-high-energy cosmic-rays (UHECRs), based on the simultaneous observation of two or more photons from the same Galactic hadron jet. We derive a general formula allowing one to calculate the probability of detecting such `multiple events', for any particular top-down model, once the physical parameters of the associated hadron jets are known. We then apply our results to a generic top-down model involving the decay of a supermassive particle, and show that under reasonable assumptions the next-generation UHECR detectors would be able to detect multiple events on a timescale of a few years, depending on the mass of the top-down progenitor. Either the observation or the non-observation of such events will provide constraints on the UHECR top-down models and/or the physics of hadronization at ultra-high energy.