Effective theory approach to unstable particle production

Abstract

Using the hierarchy of scales between the mass, $M$, and the width, $\hat{I}“$, of a heavy, unstable particle we construct an effective theory that allows calculations for resonant processes to be systematically expanded in powers of the coupling $\hat{I}\pm$ and $\hat{I}“/M$. We illustrate the method by computing the next-to-leading order line shape of a scalar resonance in an abelian gauge-Yukawa model.

4 pages, 1 figure