An alternative explanation for the $\Theta(1540)$ pentaquark peak

Abstract

We have studied the $\gamma d \to K^+ K^- n p$ reaction in which the LEPS collaboration found a signal in the $K^+ n$ invariant mass for the claimed $\Theta(1540)$ pentaquark peak. Our study reveal that the procedure used at LEPS to reconstruct the $K^+n$ invariant mass generates an artificial strength in the $\Theta(1540)$ region and that the LEPS collaboration underestimated the background in that region, such that the signal observed for the $\Theta(1540)$ is compatible with a fluctuation of $2\sigma$ over the calculated background.