  Explicit field theory computations are carried out of the joint probabilities
associated with spin correlations of $\mu^{-}\mu^{+}$ produced in $e^{-}e^{+}$
collision in the standard electroweak model to the leading order. The derived
expressions are found to depend not only on the speed of the $e^{-}e^{+}$ pair
but also on the underlying couplings. These expressions are unlike the ones
obtained from simply combining the spins of the relevant particles which are of
kinematical nature. It is remarkable that these explicit results obtained from
quantum field theory show a clear violation of Bell's inequality.
