Model dependence of single-energy fits to pion photoproduction data

TL;DR

This study investigates how model choices affect the extraction of pion photoproduction amplitudes, demonstrating that different fitting approaches can yield consistent results within certain energy ranges and under specific conditions.

Contribution

It introduces a comprehensive analysis of model dependence in multipole fits to pion photoproduction data using both energy-dependent and single-energy methods.

Findings

Single-energy fits are consistent with input amplitudes from MAID.

Fits achieve a chi-squared per datum of unity or less.

Sensitivity of fits depends on polarization observables and energy regions.

Abstract

Model dependence of multipole analysis has been explored through energy-dependent and single-energy fits to pion photoproduction data. The MAID energy-dependent solution has been used as input for an event generator producing realistic pseudo data. These were fitted using the SAID parametrization approach to determine single-energy and energy-dependent solutions over a range of lab photon energies from 200 to 1200 MeV. The resulting solutions were found to be consistent with the input amplitudes from MAID. Fits with a $\chi$-squared per datum of unity or less were generally achieved. We discuss energy regions where consistent results are expected, and explore the sensitivity of fits to the number of included single- and double-polarization observables. The influence of Watson's theorem is examined in detail.