Study of the Decay $B^{0}_{s} \to J/\psi\phi \to \mu^{+}\mu^{-}K^{+}K^{-}$

A study of the decay bs->psi phi is presented, with a description of a possible selection strategy and a maximum likelihood fit of the angular distribution of the final decay products. Prospects for the measurement of the difference of the width of the weak eigenstates of the bs are given for an untagged analysis.