Renormalon

In quantum field theory, a renormalon is a "power-like" infrared-sensitive contribution to a hard (high-energy) process, as opposed to the usual logarithmic infrared-sensitive effects encountered in quantum chromodynamics (QCD) calculations. For example, the relation between the pole mass of a quark "Q" and the physical observables from which it can be extracted suffers from a renormalon ambiguity, which is a relative correction of order $Lambda\_\{QCD\}/m\_Q$. The usual logarithmic infrared-sensitive effects in QCD go like $log(Lambda\_\{QCD\}/m\_Q)$.