[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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