Speaker
Mr
Stefan Ropertz
(University of Bonn)
Description
Dispersion theory is a powerful tool for partial wave analyses of decay and scattering processes involving light mesons. However, as a result of the onset of various inelastic channels, its simple single- or two-channel implementations can in practice be applied only up to energies of about $1.1$ GeV. In this talk we introduce an effective parametrization for the isoscalar, scalar pion form factor which preserves the principles of analyticity and unitarity. Furthermore it allows us to introduce higher resonances and inelastic channels and at the same time matches smoothly on the dispersive representation at low energies. We show how it can be applied to decays $\bar{B}_s^0 \rightarrow J/\psi\,\pi^+\pi^-(K^+K^-)$ measured by LHCb. Since the parametrization is analytic it allows us to explore the structure of the form factor in the complex plane giving rise to resonance poles. In order to extract those we use the model-independent and easily applicable approach of Pad\'e approximants.
Primary author
Mr
Stefan Ropertz
(University of Bonn)
Co-authors
Dr
Bastian Kubis
(University of Bonn)
Dr
Christoph Hanhart
(Forschungszentrum Jülich Institute for Nuclear Physics)
