Polarization of $\Lambda (1405)$ in the $\gamma p\to K^{+}\pi \Sigma$ reaction

Abstract

In this paper, we study the polarization of the $\Lambda (1405)$ in the $\gamma p\to K^{+}\pi \Sigma$ reaction within an effective Lagrangian approach and isobar model. In our model, the $\Lambda (1405)$ is excited through the t-channel $K/K^{\ast }$ exchanges and u-channel hyperon exchange. Compared to previous studies, we also include the contribution from a contact term, which is necessary for our model to interpret the polarization of the $\Lambda (1405)$. In addition, we also discuss the possibility to verify the proposed two-pole structure of the $\Lambda (1405)$ using the polarization data. We find that the polarization of the $\Lambda (1405)$ or the polarization of the final $\Sigma$ in this reaction is sensitive to the invariant mass $M_{\pi \Sigma }$. Thus the measurement of the dependence of the $\Lambda (1405)$ polarization on the $M_{\pi \Sigma }$ can offer valuable information about the pole structure of the $\Lambda (1405)$.

Comments: 8 pages, 7 figures. Version accepted by PLB