Laurent+Pietarinen Partial Wave Analysis

Abstract: A new energy-dependent fit strategy, independent of any specific microscopic theory, is applied to kaon photoproduction data with center-of-mass energies ranging from 1625 MeV to 2296 MeV. Experimental data are fitted in terms of a modified Laurent expansion (Laurent+Pietarinen expansion) which previously has been successfully applied to multipoles. The present aim is to extract resonance pole parameters directly from the data, rather than from sets of multipoles. A constrained single-energy fit is then used to search for missing structures. In this proof-of-principle study, the data are well-described by the initial L+P fit, and it is shown that only a moderate amount of structure, mostly in higher multipoles, is missing from the original fit. Problems due to an unmeasurable overall phase, plaguing single-channel multipole analyses, are mitigated by implementing a form of phase limitation, fixing the initial values of fit parameters using a multi-channel analysis.