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Register a new userMeasurements of B- -> D(*)0 K(*)- Decays Related to gamma
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Giampiero Mancinelli
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We present measurements of branching fractions and CP asymmetries of several B- -> D(*)0 K(*)- decays, with the D(*)0 decaying to CP-even, CP-odd, and flavor eigenstates, that can constrain the CP angle gamma as well as the amplitude ratio rb=A(B -> u)/A(B -> c), using methods proposed by Gronau, London and Wyler or Atwood, Dunietz and Sony. We use data collected with the BABAR detector at the PEP-II asymmetric energy e+e- collider at SLAC.
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The B -> D^{(*)} K^- K^{(*)0} decays have been observed for the first time. The branching fractions of the B -> D^{(*)} K^- K^{(*)0} decay modes are measured. Significant signals are found for the B -> D^{(*)} K^- K^{*0} and B^- -> D^0 K^- K^0_S decay modes. The invariant mass and polarization distributions for the K^-K^{*0} and K^-K^0_S subsystems have been studied. For the K^-K^{*0} sybsystem these distributions agree well with those expected for two-body B -> D^{(*)} a_1^-(1260) decays, with a_1^-(1260) -> K^- K^{*0}. The analysis was done using 29.4 fb^{-1} of data collected with the Belle detector at the e^+ e^- asymmetric collider KEKB.
The decay mode $B^{0}_{s} to D^{mp}_{s} K^{pm} $ allows for one of the theoretically cleanest measurements of the CKM angle $gamma$ through the study of time-dependent $ensuremath{CP}xspace$ violation. This paper reports a measurement of its branching fraction relative to the Cabibbo-favoured mode $B^{0}_{s} to D^{-}_{s} pi^{+}$ based on a data sample of 0.37 fb$^{-1}$ proton-proton collisions at $sqrt{s} = 7$ TeV collected in 2011 with the LHCb detector. In addition, the ratio of $ensuremath{mathrm{B}}xspace$ meson production fractions $ensuremath{f_s/f_d}$, determined from semileptonic decays, together with the known branching fraction of the control channel $B^{0} to D^{-} pi^{+}$, is used to perform an absolute measurement of the branching fractions: $B (B^0_s to D^-_s pi^+) ;= (2.95 pm 0.05 pm 0.17^{,+,0.18}_{,-,0.22}) times 10^{-3}$, $B (B^0_s to D^mp_s K^pm) = (1.90 pm 0.12 pm 0.13^{,+,0.12}_{,-,0.14}) times 10^{-4},$, where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to $f_s/f_d$.
The first observation of the $B^0_stobar{D}^0 K^0_S$ decay mode and evidence for the $B^0_stobar{D}^{*0} K^0_S$ decay mode are reported. The data sample corresponds to an integrated luminosity of 3.0 $text{fb}^{-1}$ collected in $pp$ collisions by LHCb at center-of-mass energies of 7 and 8 TeV. The branching fractions are measured to be begin{align*} mathcal{B}(B^0_stobar{D}^0 bar{K}^0) &= (4.3pm0.5(text{stat})pm0.3(text{syst})pm0.3(text{frag})pm0.6(text{norm}))times10^{-4}, mathcal{B}(B^0_stobar{D}^{*0} bar{K}^0) &= (2.8pm1.0(text{stat})pm0.3(text{syst})pm0.2(text{frag})pm0.4(text{norm}))times10^{-4}, end{align*} where the uncertainties are due to contributions coming from statistical precision, systematic effects, and the precision of two external inputs, the ratio $f_s/f_d$ and the branching fraction of $B^0tobar{D}^0 K^0_S$, which is used as a calibration channel.
A binned Dalitz plot analysis of the decays $B^0 to D K^{ast 0}$, with $D to K_{S}^{0} pi^{+} pi^{-}$ and $K_{S}^{0} K^{+} K^{-}$, is performed to measure the observables $x_pm$ and $y_pm$, which are related to the CKM angle $gamma$ and the hadronic parameters of the decays. The $D$ decay strong phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of the $D$ decay model. With a sample of proton-proton collision data, corresponding to an integrated luminosity of $3.0,rm{fb}^{-1}$, collected by the LHCb experiment, the values of the $CP$ violation parameters are found to be $x_+ = 0.05 pm 0.35 pm 0.02$, $x_-=-0.31pm 0.20 pm 0.04$, $y_+=-0.81pm 0.28pm 0.06$ and $y_-=0.31pm 0.21 pm 0.05$, where the first uncertainties are statistical and the second systematic. These observables correspond to values $gamma$ = $(71 pm 20)^circ$, $r_{B^0} = 0.56pm 0.17$ and $delta_{B^0} = (204,^{+21}_{-20})^circ$. The parameters $r_{B^0}$ and $delta_{B^0}$ are the magnitude ratio and strong phase difference between the suppressed and favoured $B^0$ decay amplitudes, and have been measured in a region of $pm 50$ MeV/$c^2$ around the $K^{ast}(892)^{0}$ mass and with the magnitude of the cosine of the $K^{ast}(892)^{0}$ helicity angle larger than 0.4.
A model-dependent amplitude analysis of the decay $B^0rightarrow D(K^0_Spi^+pi^-) K^{*0}$ is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0fb$^{-1}$, recorded at $sqrt{s}=7$ and $8 TeV$ by the LHCb experiment. The CP violation observables $x_{pm}$ and $y_{pm}$, sensitive to the CKM angle $gamma$, are measured to be begin{eqnarray*} x_- &=& -0.15 pm 0.14 pm 0.03 pm 0.01, y_- &=& 0.25 pm 0.15 pm 0.06 pm 0.01, x_+ &=& 0.05 pm 0.24 pm 0.04 pm 0.01, y_+ &=& -0.65^{+0.24}_{-0.23} pm 0.08 pm 0.01, end{eqnarray*} where the first uncertainties are statistical, the second systematic and the third arise from the uncertainty on the $Drightarrow K^0_S pi^+pi^-$ amplitude model. These are the most precise measurements of these observables. They correspond to $gamma=(80^{+21}_{-22})^{circ}$ and $r_{B^0}=0.39pm0.13$, where $r_{B^0}$ is the magnitude of the ratio of the suppressed and favoured $B^0rightarrow D K^+ pi^-$ decay amplitudes, in a $Kpi$ mass region of $pm50 MeV$ around the $K^*(892)^0$ mass and for an absolute value of the cosine of the $K^{*0}$ decay angle larger than $0.4$.
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