Photoproduction of the $\Lambda$(1405) Hyperon

Abstract

We propose to use the high current photon beam available at A2 to produce the isosinglet $\Lambda(1405)1/2^-$ hyperon at threshold via $\gamma p\rightarrow K^+\Lambda(1405)$. Its nature is still controversial and actively debated. Since the only available photoproduction data from CLAS are lacking in precision in the $\Sigma^0\pi^0$ decay channel, we propose a new independent measurement of this most important pure $I = 0$ final state including the unmeasured beam-helicity observable $I^\odot$. In addition, the excellent photon detection acceptance of the A2 setup will offer the opportunity for a first measurement of the radiative decays of the $\Lambda(1405)$, which will provide clean and stringent constraints for model descriptions in terms of, e.g., unitary chiral perturbation theory.