Observation of $B_s^0\to D_s^{\ast -}{\pi }^{+}$, $B_s^0\to D_s^{(\ast )-}{\rho }^{+}$ and $B_s^0\to D_s^{(\ast )+}{D}_s^{(\ast )-}$ and Estimate of $\Delta {\Gamma }_{CP}$ at Belle

Abstract

The large data sample being recorded with the Belle detector at the ${\rm Y}$(5S) energy provides a unique opportunity to study the less-well-known $B_s^0$ meson decays. Following our recent measurement of $B_s^0\to D_s^{-}{\pi }^{+}$ in a sample of 23.6 fb${}^{-1}$, we extend the analysis to include decays with photons in the final state. Using the same sample, we report the first observation of three other dominant exclusive $B_s^0$ decays, in the modes $B_s^0\to D_s^{\ast -}{\pi }^{+}$, $B_s^0\to D_s^{-}{\rho }^{+}$ and $B_s^0\to D_s^{\ast -}{\rho }^{+}$. We measure their respective branching fractions and, using helicity-angle distributions, the longitudinal polarization fraction of the $B_s^0\to D_s^{\ast -}{\rho }^{+}$ decay. We also present a measurement of the branching fractions for the decays $B_s^0\to D_s^{(\ast )+}{D}_s^{(\ast )-}$. In the heavy quark limit, this branching fraction is directly related to the width difference between the $B_s$ CP-even and CP-odd eigenstates.

arXiv comment4 pages, 2 figures, To appear in the proceedings of the "35th International Conference On High Energy Physics: ICHEP 2010", 21-28 July 2010, Paris, France