  In this talk we show that, unlike other pure $b\to d$ penguin processes, the
decay $\bs(t)\to\phi\ks$ is dominated by a single amplitude, that of the
internal $t$-quark. Thus, the indirect CP asymmetry in this decay probes $\sin
2\beta$. This cancellation holds for most part of the parameter space and error
on $\sin 2\beta$ is less than 10%. By measuring the direct CP asymmetry, one
can get a better idea of the probable error on $\sin 2\beta$.
