# 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. b2dsph[..].pdf [7 KiB] HiDef png [53 KiB] Thumbnail [102 KiB] *.C file b2dkst[..].pdf [7 KiB] HiDef png [56 KiB] Thumbnail [89 KiB] *.C file b2dsks[..].pdf [7 KiB] HiDef png [57 KiB] Thumbnail [89 KiB] *.C file 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. B2Dsphi.pdf [27 KiB] HiDef png [381 KiB] Thumbnail [297 KiB] *.C file 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 ${\sigma =13.8}$ ${\mathrm{ Me V /}c^2}$ 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. dkstar[..].pdf [14 KiB] HiDef png [229 KiB] Thumbnail [191 KiB] *.C file dkstar[..].pdf [14 KiB] HiDef png [273 KiB] Thumbnail [216 KiB] *.C file dsksta[..].pdf [14 KiB] HiDef png [256 KiB] Thumbnail [204 KiB] *.C file dsksta[..].pdf [14 KiB] HiDef png [227 KiB] Thumbnail [187 KiB] *.C file Animated gif made out of all figures. PAPER-2012-025.gif Thumbnail

## 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] HiDef png [43 KiB] Thumbnail [19 KiB] tex code Systematic uncertainties contributing to $\mathcal{B}( B^{+} \rightarrow D_s^{+}\phi )/\mathcal{B}( B ^+ \rightarrow D ^+_ s \overline{ D }{} ^0 )$. Table_2.pdf [16 KiB] HiDef png [58 KiB] Thumbnail [25 KiB] tex code 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. Table_3.pdf [53 KiB] HiDef png [43 KiB] Thumbnail [21 KiB] tex code 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. Table_4.pdf [53 KiB] HiDef png [52 KiB] Thumbnail [26 KiB] tex code

Created on 01 June 2020.