Origin of the second peak in the cross section of the $K^+Λ$ photoproduction

Abstract

By using a covariant isobar model and the latest experimental data we have analyzed the role of the $P_{13}(1900)$ and $D_{13}(2080)$ resonances in the kaon photoproduction process $γp\to K^+Λ$. Special attention has been paid to the region where the second peak in the cross section is located, i.e. at total c.m. energies around 1.9 GeV. It is found that this peak originates mostly from the $P_{13}(1900)$ resonance contribution. Although the contribution of the $D_{13}(2080)$ resonance is not negligible, it is much smaller than that of the $P_{13}(1900)$ state. Our finding confirms that the $P_{13}(1900)$ resonance is also important in explaining the beam-recoil double polarization data $C_x$ and $C_z$, provided that the mass and the width of this resonance are 1871 and 131 MeV, respectively.