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Register a new userAngular analysis of $B^0 to D^{*-}D_s^{*+}$ with $D_s^{*+} to D_s^+ gamma$ decays
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The first full angular analysis of the $B^0 to D^{*-} D_s^{*+}$ decay is performed using 6 fb$^{-1}$ of $pp$ collision data collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The $D_s^{*+} to D_s^+ gamma$ and $D^{*-} to bar{D}^0 pi^-$ vector meson decays are used with the subsequent $D_s^+ to K^+ K^- pi^+$ and $bar{D}^0 to K^+ pi^-$ decays. All helicity amplitudes and phases are measured, and the longitudinal polarisation fraction is determined to be $f_{rm L} = 0.578 pm 0.010 pm 0.011$ with world-best precision, where the first uncertainty is statistical and the second is systematic. The pattern of helicity amplitude magnitudes is found to align with expectations from quark-helicity conservation in $B$ decays. The ratio of branching fractions $[mathcal{B}(B^0 to D^{*-} D_s^{*+}) times mathcal{B}(D_s^{*+} to D_s^+ gamma)]/mathcal{B}(B^0 to D^{*-} D_s^+)$ is measured to be $2.045 pm 0.022 pm 0.071$ with world-best precision. In addition, the first observation of the Cabibbo-suppressed $B_s^0 to D^{*-} D_s^+$ decay is made with a significance of seven standard deviations. The branching fraction ratio $mathcal{B}(B_s^0 to D^{*-} D_s^+)/mathcal{B}(B^0 to D^{*-} D_s^+)$ is measured to be $0.049 pm 0.006 pm 0.003 pm 0.002$, where the third uncertainty is due to limited knowledge of the ratio of fragmentation fractions.
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The $CP$ asymmetry in $B^-to D_s^-D^0$ and $B^-to D^-D^0$ decays is measured using LHCb data corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. The results are $A^{CP}(B^-to D_s^-D^0)=(-0.4pm 0.5pm 0.5)%$ and $A^{CP}(B^-to D^-D^0)=( 2.3pm 2.7pm 0.4)%$, where the first uncertainties are statistical and the second systematic. This is the first measurement of $A^{CP}(B^-to D_s^-D^0)$ and the most precise determination of $A^{CP}(B^-to D^-D^0)$. Neither result shows evidence of $CP$ violation.
We report a measurement of the $B^0$ and $B^+$ meson decays to the $D_s^-K^0_S pi^+$ and $D_s^- K^+K^+$ final states, respectively, using $657 times 10^{6} Boverline{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Using the $D_s^-to phipi^-$, $K^{*}(892)^0 K^-$ and $K^0_S K^-$ decay modes for the $D_s$ reconstruction, we measure the following branching fractions: ${cal B}(B^0to D_s^{-}K^0_Spi^+)=[0.47 pm 0.06 (mathrm {stat}) pm 0.05 (mathrm {syst})]times 10^{-4}$ and ${cal B}(B^+to D_s^-K^+K^+)= [0.93 pm 0.22 (mathrm {stat})pm 0.10 (mathrm {syst})]times 10^{-5}$. We find the ratio of the branching fraction of $B^+to D_s^-K^+K^+$ to that of the analogous Cabibbo favored $B^+to D_s^-K^+pi^+$ decay to be ${cal R}_{cal B} = 0.054 pm 0.013 ({rm stat}) pm 0.006 ({rm syst})$, which is consistent with the na{i}ve factorization model. We also observe a deviation from the three-body phase-space model for both studied decays.
A search for $B^{+} to D_s^{+}K^{+}K^{-}$ decays is performed using $pp$ collision data corresponding to an integrated luminosity of 4.8 fb$^{-1}$, collected at centre-of-mass energies of 7, 8 and 13$,$TeV with the LHCb experiment. A significant signal is observed for the first time and the branching fraction is determined to be begin{equation*} mathcal{B}(B^{+} to D_s^{+}K^{+}K^{-} ) = (7.1 pm 0.5 pm 0.6 pm 0.7) times 10^{-6}, end{equation*} where the first uncertainty is statistical, the second systematic and the third due to the uncertainty on the branching fraction of the normalisation mode $B^{+} to D_s^{+} overline{kern -0.2em D}^{0}$. A search is also performed for the pure annihilation decay $B^{+} to D_s^{+}phi$. No significant signal is observed and a limit of begin{equation*} mathcal{B}(B^{+} to D_s^{+}phi) < 4.9 times 10^{-7}~(4.2 times 10^{-7}) end{equation*} is set on the branching fraction at 95$%$ (90$%$) confidence level.
Using the CLEO~II detector we measure ${cal B}(D_s^+to eta e^+ u)/{cal B}(D_s^+to phi e^+ u) =1.24pm0.12pm0.15$, ${cal B}(D_s^+to eta e^+ u)/{cal B}(D_s^+to phi e^+ u) =0.43pm0.11pm0.07$ and ${cal B}(D_s^+to eta e^+ u)/{cal B}(D_s^+to eta e^+ u) =0.35pm0.09pm0.07$. We find the vector to pseudoscalar ratio, ${cal B}(D_s^+to phi e^+ u)/{cal B}(D_s^+to (eta+eta) e^+ u) =0.60pm0.06pm0.06$, which is similar to the ratio found in non strange $D$ decays.
The first measurement of the effective lifetime of the $bar{B}_s^0$ meson in the decay $bar{B}_s^0to D_s^-D_s^+$ is reported using a proton-proton collision dataset, corresponding to an integrated luminosity of 3 fb$^{-1}$, collected by the LHCb experiment. The measured value of the $bar{B}_s^0to D_s^-D_s^+$ effective lifetime is $1.379pm0.026pm0.017$ ps, where the uncertainties are statistical and systematic, respectively. This lifetime translates into a measurement of the decay width of the light $bar{B}_s^0$ mass eigenstate of Gamma_L$=0.725pm0.014pm0.009$ ps$^{-1}$. The $bar{B}_s^0$ lifetime is also measured using the flavor-specific $bar{B}_s^0to D^-D_s^+$ decay to be $1.52pm0.15pm0.01 {rm ps}$.
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