$\Theta^{+}$ Search in CLAS with $\gamma d\rightarrow pK^{0}_{s}K^{-}(p)$*

A search for photo-production of the $\Theta^{+}(1540)$ pentaquark in the $pK^{0}$ decay mode was performed with the CLAS detector at Jefferson Lab. About $20,000$ $\gamma d\rightarrow pK^{0}_{s}K^{-}(p)$ events with photon beam energies $1.6-3.6GeV$ were fully reconstructed and kinematically fitted. To investigate the resonant backgrounds, a phenomological model including hyperon and meson production has been developed and fitted to the data w ith a maximum-likelihood method. The model results serve as a background to evaluate the existence of a pentaquark signal in the invariant mass of the $pK^{0}$ system. The cross-section upper limit on $\Theta^{+}$ photo-production in this channel will be reported.