An Effective Field Theory for the Three-Body System

Abstract

We study the scattering of a particle from a bound pair in an effective field theory using a distorted-wave renormalisation group method to find the power-counting for the three-body force terms. We find that three-body terms appear at lower orders than naively expected. They start with a marginal term that varies as a logarithm rather than a power of the energy scales in the problem. The marginal term has important implications for the three-body problem in nuclear physics.