Constraining the mass and width of the N^*(1685) resonance

We have examined the existence of the N^*(1685) resonance, which is recently listed by the Particle Data Group as a one-star nucleon resonance, by using a covariant isobar model for kaon photoproduction and assuming that the resonance has Jp=1/2⁺, in accordance with our previous finding. After the inclusion of this resonance, the changes in the total χ2 show two clear minima at MN^*=1650 and 1696 MeV, which correspond to two different resonance states. The former corresponds to the narrow nucleon resonance found in our previous investigation, whereas the latter corresponds to a new resonance found as we increase the resonance width. From the latter we derive the mass and width relation of the N ^*(1685) resonance. We observe that the properties of both the N^*(1685) and N^*(1710)P₁₁ resonances are strongly correlated. Although the best fit of the present work yields MN^*=1696 MeV and ΓN^*=76 MeV, the apparently small N^*(1710)P₁₁ coupling constant to the K⁺Λ channel found in previous investigations suggests that ΓN^*â‰35 MeV, which, according to the mass and width relation, corresponds to MN^*â‰1680 MeV.