Torus or black disk?

Abstract

We show that the interaction region of colliding protons looks completely absorptive (black) at the impact parameters up to 0.4 - 0.5 fm at the LHC energy 7 TeV. It is governed by the ratio of the elastic diffraction peak slope to the total cross section. The corresponding parameter is approximately equal to 1 at the LHC. The behavior of this ratio at higher energies will show if this region will evolve to the black disk or to the black torus. Recent fits at 7 TeV can not distinguish between these possibilities within the limits of experimental indefiniteness and of extrapolations in the regions of unmeasured transferred momenta.

Comments: 8 pages, 2 Figs, Bulletin of the Lebedev Physics Institute. arXiv admin note: substantial text overlap with arXiv:1401.3106