Measurement of Branching Fractions and Charge Asymmetries in $B$ Decays to an $\eta$ Meson and a $K^{*}$ Meson

We present measurements of branching fractions and charge asymmetries for the decays $B\to \eta K^{*}$, where $K^{*}$ indicates a spin 0, 1, or 2 $K\pi$ system. The data sample corresponds to $344\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at SLAC. We measure the branching fractions (in units of ${10}^{-6}$): $\mathcal{B}\mathbf{(}{B}^0\to \eta K^{*0}(892)\mathbf{)}=16.5\pm 1.1\pm 0.8$, $\mathcal{B}\mathbf{(}{B}^{+}\to \eta K^{*+}(892)\mathbf{)}=18.9\pm 1.8\pm 1.3$, $\mathcal{B}\mathbf{(}{\mathrm{B}}^0\to \eta (K\pi {)}_0^{*0}\mathbf{)}=11.0\pm 1.6\pm 1.5$, $\mathcal{B}\mathbf{(}{\mathrm{B}}^{+}\to \eta (K\pi {)}_0^{*+}\mathbf{)}=18.2\pm 2.6\pm 2.6$, $\mathcal{B}\mathbf{(}{\mathrm{B}}^0\to \eta K_2^{*0}(1430)\mathbf{)}=9.6\pm 1.8\pm 1.1$, and $\mathcal{B}\mathbf{(}{\mathrm{B}}^{+}\to \eta K_2^{*+}(1430)\mathbf{)}=9.1\pm 2.7\pm 1.4$. We also determine the charge asymmetries for all decay modes.

Figure 1

$B$-candidate $m_{\mathrm{ES}}$ projections obtained with a cut on the signal likelihood (see text) for (a) $B^0\to \eta K^{*0}(892)$, (b) $B^0\to \eta (K\pi {)}_0^{*0}$ (long-dashed, red) plus $B^0\to \eta K_2^{*0}(1430)$ (short-dashed, blue), (c) $B^{+}\to \eta K^{*+}(892)$, and (d) $B^{+}\to \eta (K\pi {)}_0^{*+}$ (long-dashed, red) plus $B^0\to \eta K_2^{*0}(1430)$ (short-dashed, blue). Points with uncertainties represent the data, solid curves the full fit functions, and dotted curves the full background functions.

Figure 2

Projection of the signals in the HMR, obtained with a cut on the signal likelihood (see text): $K\pi$ mass for (a) $B^0$, and (c) $B^{+}$ channels; $\mathcal{H}$ for (b) $B^0$, and (d) $B^{+}$ channels. Points with uncertainties represent the data, solid curves the full fit functions, dotted curves the $(K\pi {)}_0^{*}$ portion, dot-dashed curves the $K_2^{*}(1430)$ portion, and dashed curves the full background functions.