Unstable-particle effective field theory

Abstract

Unstable particles are notorious in perturbative quantum field theory for producing singular propagators in scattering amplitudes that require regularization by the finite width. In this review I discuss the construction of an effective field theory for unstable particles, based on the hierarchy of scales between the mass, M, and the width,Gamma, of the unstable particle that allows resonant processes to be systematically expanded in powers of the coupling alpha and Gamma/M, thereby providing gauge-invariant approximations at every order. I illustrate the method with the next-to-leading order line-shape of a scalar resonance in an abelian gauge-Yukawa model, and results on NLO and dominant NNLO corrections to (resonant and non-resonant) pair production of W-bosons and top quarks.

14 pages, LaTeX, 12 figures, to appear in Nucl. Phys. (Proc. Suppl.) ,"Advances in Computational Particle Physics", Proceedings of the Final Meeting of the Collaborative Research Centre / Transregio 9 "Computational Particle Physics", Durbach, Germany, September 2014

References in corpus (4)

• Mixed QCD-electroweak O(α_sα) corrections to Drell-Yan processes in the resonance region: pole approximation and non-factorizable corrections
• Four-fermion production near the W pair production threshold
• Ultrasoft contribution to heavy-quark pair production near threshold
• Dominant NNLO corrections to four-fermion production near the W-pair production threshold