A Genetic Algorithm Analysis of N* Resonances in $p(\gamma,K^{+})\Lambda$ Reactions

Abstract

The problem of extracting information on new and known $N^{*}$ resonances by fitting isobar models to photonuclear data is addressed. A new fitting strategy, incorporating a genetic algorithm, is outlined. As an example, the method is applied to a typical tree-level analysis of published $p(\gamma,K^{+})\Lambda$ data. It is shown that, within the limitations of this tree-level analysis, a resonance in addition to the known set is required to obtain a reasonable fit. An additional $P_{11}$ resonance, with a mass of about 1.9 GeV, gives the best agreement with the published data, but additional $S_{11}$ or $D_{13}$ resonances cannot be ruled out. Our genetic algorithm method predicts that photon beam asymmetry and double polarization $p(\gamma,K^{+})\Lambda$ measurements should provide the most sensitive information with respect to missing resonances.