Rapidity gap survival probability and total cross sections 1

We discuss recent calculations of the survival probability of the large rapidity gaps in exclusive processes of the type pp → p+ A+ p at high energies. Absorptive or screening effects are important, and one consequence is that the total cross section at the LHC is predicted to be only about 90 mb. At the LHC, the observation of an exclusive process of the type pp → p + A + p, where a produced new heavy object A is separated from the outgoing protons by large rapidity gaps (LRG), will provide very good experimental conditions to study the properties of object A [1, 2, 3]. The process is sketched in Fig. 1. The case of A = H → bb̄ is particularly interesting. Thecross is usually written in the form