The Black Hole of Geneva

Black holes are known as the omnivorous destroyers of stars. In reality black holes not only take but give. Near their event horizons, where space is so drastically warped, black holes spawn particle-antiparticle pairs out of sheer vacuum. In some cases one of the pair escapes beyond the horizon while its counterpart is pulled back into the hole. Thus black holes can shed energy in the form of this "Hawking radiation."

Physicists hope to bring this whole process down to earth by manufacturing tiny black holes amid the stupendous smashups of protons at the Large Hadron Collider (LHC) being built at CERN. Until recently theorists thought gravity was so weak compared to the other forces that it, and gravitationally bound objects like black holes, could be studied on an equal footing with the other forces like the strong nuclear force only at energies of 10¹⁹ GeV.

In the past few years, though, some models featuring extra spatial dimensions hint that the unification of the forces, including gravity, might set in at much more modest energies, even in the TeV realm of the LHC. Thus one can contemplate forming a TeV-mass black hole even as one can imagine creating new particles in that mass range.

But what would a black hole look like? Savas Dimopoulos of Stanford (650-723-4231) and Greg Landsberg of Brown University (landsberg@hep.brown.edu, 401-863-1464) have drawn a picture in which proton-proton collisions could create black holes with a cross section (likelihood of creation) only about a factor of ten less than for producing top quarks and at a rate of up to one per second (see figure). A black hole produced in this way would quickly decay, not in the usual particle way but in a furious burst of Hawking radiation. A particularly striking signature of the black hole would involve an electron, muon, and photon in the final state of debris particles. Properties of Hawking radiation could tell physicists about the shape of extra spatial dimensions. A possibility of recreating the early moments of the universe in the lab would further unite particle physics and cosmology (Dimopoulous and Landsberg, Physical Review Letters, 15 October 2001.)