Using Bs(t) -> phi K_s to measure Sin 2 beta

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 $\sin 2\beta$.