Resonances and poles in the second Riemann sheet

Understand

In this work we study basic properties of unstable particles and scalar hadronic resonances, respectively, within simple quantum mechanical and quantum field theoretical (effective) models.

• We start with the basic ideas of quantum field theory.
• In particular, we introduce the Feynman propagator for unstable scalar resonances and motivate the idea that this kind of correlation function should possess complex poles which parameterize the mass and decay width of the considered particle.
• We also briefly discuss the problematic scalar sector in particle physics, emphasizing that hadronic loop contributions dominate its dynamics.