Speaker
Description
We compare the methods of amplitude reconstruction, for a complete
experiment and a truncated partial wave analysis, applied to the
photoproduction of pseudo-scalar mesons~[1]. A complete experiment
analysis (CEA) determines 4 complex amplitudes up to an overall
phase $\phi_0(E,\theta)$ at any given energy and angle and requires
a minimum set of 8 observables that must include beam-, target- and
recoil polarization, e.g. $\{d\sigma/d\Omega, \Sigma, T, P, F, G,
C_x\, \mbox{and}\, O_x \}$. On the other hand, a truncated partial
wave analysis (TPWA) determines $4\,L_{max}$ complex multipoles up
to an overall phase $\phi_0(E)$ at any given energy and is valid for
all angles. The TPWA requires a minimum set of only 4 observables,
where either target- or recoil polarization can be totally avoided.
E.g., the set $\{d\sigma/d\Omega, \Sigma, F\, \mbox{and}\; H \}$ is
already complete. Examples are given for different order of
truncation.
In an extension of this work we also discuss complete
electroproduction experiments that require 12 observables for a CEA,
whereas a TPWA can already be performed with only 6 observables.
And again, either target or recoil polarization can be avoided.
[1] R.~L.~Workman, L.~Tiator, Y.~Wunderlich, M.~D\"oring
and H.~Haberzettl, Phys.\ Rev.\ C {\bf 95}, 015206 (2017).
