Role of a triangle singularity in the $\gamma p\to K^{+}\Lambda (1405)$ reaction

Abstract

We show the effects of a triangle singularity mechanism for the $\gamma p\to K^{+}\Lambda (1405)$ reaction. The mechanism has a $N^{\ast }$ resonance around 2030 MeV, which decays into $K^{\ast }\Sigma$. The $K^{\ast }$ decays to $K^{+}\pi$, and the $\pi \Sigma$ merge to form the $\Lambda (1405)$. This mechanism produces a peak around $\sqrt{s}=2110$ MeV, and has its largest contribution around cos$\theta =0$. The addition of this mechanism to other conventional ones, leads to a good reproduction of $\mathrm{d}\sigma /\mathrm{dcos}\theta$ and the integrated cross section around this energy, providing a solution to a problem encountered in previous theoretical models.

Comments: 10 pages, 10 figures