Figure 1

Invariant mass distribution of the $\Lambda\phot$ and $\overline{\Lambda}\phot$ candidates, in two \pt intervals of $1.5 - 2.0$\,\GeVc and $6.5 - 7.0$\,\GeVc. The signal is described by a single Gaussian, and the background by a polynomial of third order. The number of \siZ candidates is evaluated within $M_{\siZ}(\pt) \pm 3$\,\MeVmass. Only statistical uncertainties are shown.