International Light Cone Advisory Committee


Light-front wavefunctions, covariant Bethe--Salpeter amplitudes, and meson elastic and transition form factors

by Pieter Maris (Iowa State University)

Both light-front wavefunctions and covariant Bethe--Salpeter
amplitudes allow us to calculate a wide range of physical observables;
however, neither the light-front wavefunctions nor the Bethe--Salpeter
amplitudes themselves are physical observables, and can therefore not
be measured directly.  On the other hand, both can be (and have been)
used to evaluate e.g. meson elastic and transition form factors,
though the range in Q^2 over which one can unambiguously evalute such
form factors without further assumptions generally differs between
light-front approaches and the Bethe--Salpeter aproach based on a
Euclidean formulation.

I will present recent results for meson light-front wavefunctions,
as well as physical observables such as elastic and transition form
factors, obtained in the Basis Light-Front Quantization approach.
I will also discuss explicitly covariant calculations of meson elastic
and transition form factors based on a Euclidean formulation of the
Dyson--Schwinger equations, and highlight the (dis)advantages of each
of these two approach.  Finally, I will indicate how one can in
principle obtain the light-front wavefunction from the Bethe--Salpeter
amplitudes using the Nakanishi integral representation, and what
bottlenecks one might encounter in practice.


Webinar at