[Jlab-seminars] Theory Center Seminar

[Mary Fox]

Theory Center Seminar
Monday, Feb. 18, 2013
CEBAF Center, Room L102
1:00 p.m. (coffee at 12:45 p.m.)

Bastian Kubis
University of Bonn


*What Can We Learn From Hadronic and Radiative Decays of Light Mesons?" *

Chiral perturbation theory offers a powerful tool for the investigation 
of light pseudoscalar mesons. It incorporates the fundamental symmetries 
of QCD, interrelates various processes, and allows to link these to the 
light quark masses. Its shortcomings lie in a limited energy range: the 
radius of convergence of the chiral expansion is confined to below 
resonance scales. Furthermore, the strongest consequences of chiral 
symmetry are manifest for pseudoscalars (pions, kaons, eta) only: vector 
mesons, e.g., have a severe impact in particular for reactions involving 
photons. In this talk, I advocate dispersions relations as another 
model-independent tool to extend the applicability range of chiral 
perturbation theory. They even allow to tackle the physics of vector 
mesons in a rigorous way. It will be shown how dispersive methods can be 
used to resum large rescattering effects, and to provide 
model-independent links between hadronic and radiative decay modes. 
Examples to be discussed will include Dalitz plot distributions of 
decays into 3 pions; and meson transition form factors, which have an 
important impact on the hadronic light-by-light-scattering contribution 
to the anomalous magnetic moment of the muon.
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