Title: Dancing in the dark: detecting a population of distant primordial black holes

Abstract: Primordial black holes (PBHs) are compact objects proposed to have formed in the early Universe from the collapse of small-scale over-densities. Their existence may be detected from the observation of gravitational waves (GWs) emitted by PBH mergers, if the signals can be distinguished from those produced by the merging of astrophysical black holes (ABHs). In this talk, I will present a new mock-data-based forecast of the capability of the Einstein Telescope (a proposed third-generation GW observatory) to identify and measure the abundance of a subdominant population of distant PBHs, using the difference in the redshift evolution of the merger rate of the two populations as a discriminant. I will describe the careful modelling of the merger rates and observational uncertainties that we followed to create the mock data and present the two independent statistical methods we used to analyse it. I will show how the more powerful, likelihood-based method revealed that PBH abundances as small as fPBH≈7×10−6 (fPBH≈2×10−6) will be distinguishable from fPBH=0 at the level of 3σ with a one year (ten year) observing run of the Einstein Telescope, a roughly 2 orders of magnitude improvement on current bounds.