CKM phaseαthroughB→a0π

We propose the decay modes $\overrightarrow{B}{a}_0(\to \eta \pi )\pi$ to determine the CKM phase $\alpha .$ One can analyze these modes through (i) the $\overrightarrow{B}{a}_0\pi$ isospin pentagon, (ii) the time dependent Dalitz plot of $B^0\mathrm{}\left(t\right)\mathrm{}\to a_0^{\pm }{\pi }^{\mp }\to \eta {\pi }^{+}{\pi }^{-},$ and (iii) the time dependence of $B^0\mathrm{}\left(t\right)\mathrm{}\to a_0^0(\to \eta {\pi }^0){\pi }^0.$ We show that the $a_0\pi$ modes have certain advantages as compared to the $\rho \pi$ modes, and strongly recommend the time dependent Dalitz plot analysis in the $a_0\pi$ channel.