Evidence for the J^p=1/2^+ narrow state at 1650 MeV in the photoproduction of KLambda

TL;DR

This study investigates the existence of a narrow J^p=1/2^+ resonance at 1650 MeV in kaon photoproduction, providing evidence supporting this specific state through phenomenological modeling and data fitting.

Contribution

The paper introduces a phenomenological approach to identify a narrow resonance at 1650 MeV in kaon photoproduction, consistent across multiple models and parameter variations.

Findings

Resonance candidate at 1650 MeV with 5 MeV width identified

Resonance mass at 1650 MeV consistent across models

Narrow resonances at other masses not excluded

Abstract

We have investigated the existence of the J^p=1/2^+ narrow resonance predicted by the chiral soliton model by utilizing the kaon photoproduction process gamma + p --> K^+ + Lambda. For this purpose we have constructed two phenomenological models based on our previous effective Lagrangian model, which are able to describe kaon photoproduction from threshold up to W = 1730 MeV. By varying the mass (width) of an inserted P_{11} resonance from 1620 to 1730 MeV (0.1 to 1 MeV and 1 to 10 MeV) a number of fits has been performed in order to search for the resonance mass. Our result indicates that the most promising candidate mass (width) of this resonance is 1650 MeV (5 MeV). Although our calculation does not exclude the possibility of narrow resonances with masses of 1680, 1700 and 1720 MeV, the mass of 1650 MeV is obtained for all phenomenological models used in this investigation. Variations of the resonance width and $K\Lambda$ branching ratio are found to have a mild effect on the chi^2. The possibility that the obtained result originates from other resonance states is also discussed.