Search for $B^0\to \varphi (K^{+}{\pi }^{-})$ decays with large $K^{+}{\pi }^{-}$ invariant mass

Motivated by the polarization anomaly in the $B\to \varphi (1020)K^{*}(892)$ decay, we extend our search for other $K^{*}$ final states in the decay $B^0\to \varphi (1020)K^{*0}$ with the $K^{*0}\to K^{+}{\pi }^{-}$ invariant mass above 1.6 GeV. The final states considered include the $K^{*}(1680{)}^0$, $K_3^{*}(1780{)}^0$, $K_4^{*}(2045{)}^0$, and a $K\pi$ spin-zero nonresonant component. We also search for $B^0\to \varphi {\overline{D}}^0$ decay with the same final state. The analysis is based on a sample of about $384\times {10}^6$ $B\overline{B}$ pairs recorded with the BABAR detector. We place upper limits on the branching fractions $\mathcal{B}(B^0\to \varphi K^{*}(1680{)}^0)<3.5\times {10}^{-6}$, $\mathcal{B}(B^0\to \varphi K_3^{*}(1780{)}^0)<2.7\times {10}^{-6}$, $\mathcal{B}(B^0\to \varphi K_4^{*}(2045{)}^0)<15.3\times {10}^{-6}$, and $\mathcal{B}(B^0\to \varphi {\overline{D}}^0)<11.7\times {10}^{-6}$ at 90% C.L. The nonresonant contribution is consistent with the measurements in the lower invariant mass range.

Figure 1

(a) Feynman diagram describing the $B^0\to \varphi K^{*0}$ decay; (b) definition of decay angles given in the rest frames of the decaying parents.

Figure 2

Distribution of the $K\pi$ invariant mass extended above 1.6 GeV from the study of $B^0\to \varphi (K^{+}{\pi }^{-})$ decays in Ref. [5]. The data distribution is shown with a requirement to enhance the signal as discussed in regard to Fig. 3 in the text. The solid (dashed) line shows the signal-plus-background (background) expected distributions. The arrows indicate the higher-mass range, 1.60 to 2.15 GeV, used in this analysis.

Figure 3

Projections onto the variables $\Delta E$ (a), $m_{\mathrm{ES}}$ (b), $m_{K\pi }$ (c), $m_{K\overline{K}}$ (d), ${\mathcal{H}}_1$ (e), and ${\mathcal{H}}_2$ (f) for the signal $B^0\to \varphi (K\pi )$ and $B^0\to \varphi {\overline{D}}^0$ candidates. The solid (dotted-dashed) line shows the signal-plus-background (background only) PDF projection, while the dashed (long-dashed) line shows PDF projection for the sum of four $B^0\to \varphi (K\pi )$ categories (for $B^0\to \varphi {\overline{D}}^0$). The pronounced $D^0$ mass peak in (c) is predominantly due to background. The $D_{(s)}^{+}$-meson veto causes the sharp acceptance dips seen in (e).