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First evidence for the annihilation decay mode $B^{+} \to D_{s}^{+} \phi$

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Abstract

Evidence for the hadronic annihilation decay mode $B^{+} \to D_s^{+}\phi$ is found with greater than $3\sigma$ significance. The branching fraction and \CP asymmetry are measured to be \mathcal{B}(B^{+} \to D_s^{+}\phi) &=& (1.87^{+1.25}_{-0.73}({\rm stat}) \pm 0.19 ({\rm syst}) \pm 0.32 ({\rm norm})) \times 10^{-6}, \mathcal{A}_{CP}(B^{+} \to D_s^{+}\phi) &=& -0.01 \pm 0.41 ({\rm stat}) \pm 0.03 ({\rm syst}). The last uncertainty on $\mathcal{B}(B^{+} \to D_s^{+}\phi)$ is from the branching fractions of the $B^+ \to D_s^+ \bar{D}{}^0$ normalization mode and intermediate resonance decays. Upper limits are also set for the branching fractions of the related decay modes $B^{+}_{(c)} \to D^{+}_{(s)} K^{*0}$, $B^{+}_{(c)} \to D^{+}_{(s)} \bar{K}{}^{*0}$ and ${B_c^{+} \to D^{+}_{s}\phi}$, including the result ${\mathcal{B}(B^+ \to D^+ K^{*0})} < 1.8 \times 10^{-6}$ at the 90% credibility level.

Figures and captions

Feynman diagrams for $ B^{+}\!\rightarrow D_s^{+}\phi$ , $ B ^+ \!\rightarrow D ^+ K ^{*0} $ and $ B ^+ \!\rightarrow D ^+_ s \overline{ K }{} ^{*0} $ decays.

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Fit results for $ B^{+}\!\rightarrow D_s^{+}\phi$ . The fit regions, as given in Table 1, are labelled on the panels. The PDF components are as given in the legend.

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Invariant mass distributions for (a) $ B ^+ \!\rightarrow D ^+ K ^{*0} $ , (b) $ B ^+ \!\rightarrow D ^+ \overline{ K }{} ^{*0} $ , (c) ${ B ^+ \rightarrow D ^+_ s K ^{*0} }$ and (d) $ B ^+ \!\rightarrow D ^+_ s \overline{ K }{} ^{*0} $ . The bins are each $4\sigma$ wide, where ${\sigma =13.8}$ $ {\mathrm{\,MeV\!/}c^2}$ is the expected width of the signal peaks (the middle bin is centred at the expected $B^+$ mass). The shaded regions are the $\mu_{\rm bkgd}\pm\sigma_{\rm bkgd}$ intervals (see Table 3) used for the limit calculations; they are taken from the truncated-Gaussian priors as discussed in the text. Spline interpolation results (solid blue line and hashed blue areas) are shown for comparison.

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dsksta[..].pdf [14 KiB]
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Animated gif made out of all figures.

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Tables and captions

Summary of fit regions for $ B ^+ \rightarrow D ^+_ s \phi$. About 89% of the signal is expected to be in region A.

Table_1.pdf [42 KiB]
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Table_1.pdf

Systematic uncertainties contributing to $\mathcal{B}( B^{+}\!\rightarrow D_s^{+}\phi )/\mathcal{B}( B ^+ \!\rightarrow D ^+_ s \overline{ D }{} ^0 )$.

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Upper limits on $\cal B (B^\pm \rightarrow D_{(s)}^{\pm} K ^{*0} )$, where $n_{\rm obs}$ is the number of events observed in each of the signal regions, while $\mu_{\rm bkgd}$ and $\sigma_{\rm bkgd}$ are the Gaussian parameters used in the background prior PDFs.

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Upper limits on $f_c/f_u \cdot \mathcal{B}(B_c \rightarrow X)$, where $n_{\rm obs}$ and $n_{\rm bkgd}$ are the number of events observed in the signal and background (sideband) regions, respectively.

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Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.