This discussion centers on the status of massive gauge bosons, specifically W and Z bosons, in quantum field theory (QFT) regarding their inclusion in in/out states. It is established that these bosons, due to their finite lifetimes and resonance nature, do not qualify as asymptotic free states and are therefore restricted to internal lines in Feynman diagrams. The conversation references the UA1 experiment and the use of electromagnetic calorimeters to detect Z bosons, emphasizing that while tracks of these particles can be observed, they do not imply their existence as real particles in the context of QFT. The distinction between resonances and virtual particles is clarified, underscoring that resonances correspond to states in the Hilbert space but do not survive to asymptotic infinity.
PREREQUISITESPhysicists, particularly those specializing in particle physics and quantum field theory, as well as students and researchers interested in the properties and behaviors of gauge bosons and their detection methods.