The total cross section at the LHC

Understand

We do not have the ability to perform precise calculations of long-range strong interaction effects, because the effective QCD coupling is not small and so we cannot use perturbation theory.

• Nevertheless, I show that we know a lot, though not nearly enough.
• As a measure of our lack of knowledge, the best prediction for the total cross section at LHC energy is 125 +/- 25 mb.