# On the spin-observables in pseudoscalar meson photoproduction

## TL;DR

This paper introduces a Pauli-spin basis approach to analyze spin-observables in pseudoscalar meson photoproduction, enabling straightforward calculation of observables and identification of complete experiments, with applications to baryon spectroscopy.

## Contribution

It presents a novel Pauli-spin basis method for analyzing reaction amplitudes, identifying new sets of observables for complete experiments, and applying model-independent partial-wave analysis.

## Key findings

- Identified new sets of eight observables for reaction amplitude determination.
- Demonstrated the utility of the Pauli-spin basis in simplifying calculations.
- Applied partial-wave analysis to eta' photoproduction near threshold.

## Abstract

Spin-observables in pseudoscalar meson photoproduction is discussed. This work is complementary to the earlier works on this topic. Here, the reaction amplitude is expressed in Pauli-spin basis which allows to calculate all the observables straightforwardly. We make use of the fact that the underlying reflection symmetry about the reaction plane can be most conveniently and easily exploited in this basis to help finding the non-vanishing and independent observables in this reaction. The important issue of complete experiments is reviewed. By expressing the reaction amplitude in Pauli-spin basis, many sets of eight observables - distinct from those found in earlier works from the amplitude in transversity basis - capable of determining the reaction amplitude up to an overall phase are found. It is also shown that some of the combinations of the spin observables are suited for studying certain aspects of the reaction dynamics. We, then, carry out a (strictly) model-independent partial-wave analysis, in particular, of the peculiar angular behavior of the beam asymmetry observed in eta' photoproduction very close to threshold [P. Levi Sandri et al. 2015 Eur. Phys. J. A 51, 77]. This work should be useful, especially, for newcomers in the field of baryon spectroscopy, where the photoproduction reactions are a major tool for probing the baryon spectra.