On the potential catastrophic risk from metastable quantum-black holes produced at particle colliders

Microscopic black holes that might be produced at the LHC are usually assumed to evaporate harmlessly and essentially instantaneously via Hawking radiation. Using a quantum-mechanical treatment, I consider a scenario in which a collider-produced black hole is *metastable* rather than either perfectly stable or instantly evaporating, and in which it accretes ambient matter at the Eddington limit shortly after its production. In this scenario the Hawking radiation emitted during accretion could be harmful to Earth and/or to CERN. I argue that such black holes would remain undetectable in existing astrophysical observations, so the astrophysical bounds invoked by Giddings & Mangano (2008) and Koch, Bleicher & Stöcker (2009) do not exclude the relevant region of parameter space. I propose feasible operational measures at colliders to reduce the remaining risk.

Because the dangerous region is, by his argument, unconstrained by current observation, Plaga concludes that the published risk analyses do not establish that the residual probability of catastrophe is negligible. He recommends precautionary operational measures.

In a follow-up note (arXiv:0808.4087, 29 August 2008), Steven Giddings and Michelangelo Mangano responded that Plaga's scenario is internally inconsistent: the same physics that would allow a black hole to accrete and radiate as Plaga describes also forces it into the regime where their astrophysical bounds apply, so the proposed "gap" does not exist. Casadio, Fabi and Harms (2009, published in Physical Review D) separately argued that catastrophic growth does not occur in the scenario Plaga considers. Plaga revised the paper in response to these criticisms; as of those revisions it had not been published in a peer-reviewed journal. It remains the most-cited stated dissent from the LHC black hole safety consensus.