Speaker
Description
Experimental data for pion photoproduction including
differential cross sections and various polarization observables
from four reaction channels, γp→π0p, γp→π+n, γn→π−p and γn→π0n from
threshold up to W=2.2~GeV have been used in order to perform a
single-energy partial wave analysis with minimal model dependence by
imposing constraints from unitarity and fixed-t analyticity in an
iterative procedure. Reaction models were only used as starting
point in the very first iteration. We demonstrate that with this
procedure partial wave amplitudes can be obtained which show only a
minimal dependence on the initial model assumptions.
We have performed a fixed-t single-energy partial wave analysis of pion
photoproduction in full isospin on the world collection of data. In
an iterative two-step process the single-energy multipoles are
constrained by fixed-t Pietarinen expansions fitted to
experimental data. This leads to a partial wave expansion that obeys
fixed-t analyticity with a least model dependence. In the energy
range of W=1.09−2.20~GeV we have obtained electric and magnetic
multipoles Eℓ±,Mℓ±, up to F waves.
We compared our four SE solutions in their predictions for unmeasured
polarization observables. At lower energies the spread of these
predictions is rather small, but it becomes larger at higher
energies, where it will help to propose new measurements in order to
get a unique PWA.
