Effective theory approach to unstable particle production

Abstract

Using the hierarchy of scales between the mass, $M$, and the width, $Γ$, 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 $α$ and $Γ/M$. We illustrate the method by computing the next-to-leading order line shape of a scalar resonance in an abelian gauge-Yukawa model.

Figures (1)

• Figure 1: The line shape (in GeV$^{-2})$ in the effective theory at LO (light grey/magenta dashed) and NLO (light grey/magenta) and the LO cross section off resonance in the full theory (dark grey/blue dashed) as a function of the center-of-mass energy (in GeV).