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Register a new userMeasurement of the decay $Bto Dell u_ell$ in fully reconstructed events and determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$
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We present a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ using the decay $Bto Dell u_ell$ ($ell=e,mu$) based on 711 fb$^{-1}$ of $e^+e^-to Upsilon(4S)$ data recorded by the Belle detector and containing $772 times 10^6$ $Bbar{B}$ pairs. One $B$ meson in the event is fully reconstructed in a hadronic decay mode while the other, on the signal side, is partially reconstructed from a charged lepton and either a $D^+$ or $D^0$ meson in a total of 23 hadronic decay modes. The isospin-averaged branching fraction of the decay $Bto Dell u_ell$ is found to be $mathcal{B}(B^0 to D^- ell^+ u_{ell})=(2.31pm 0.03(mathrm{stat})pm 0.11(mathrm{syst}))%$. Analyzing the differential decay rate as a function of the hadronic recoil with the parameterization of Caprini, Lelouch and Neubert and using the form-factor prediction $mathcal{G}(1)=1.0541pm 0.0083$ calculated by FNAL/MILC, we obtain $eta_mathrm{EW}|V_{cb}|=(40.12pm 1.34)times 10^{-3}$, where $eta_mathrm{EW}$ is the electroweak correction factor. Alternatively, assuming the model-independent form-factor parameterization of Boyd, Grinstein and Lebed and using lattice QCD data from the FNAL/MILC and HPQCD collaborations, we find $eta_mathrm{EW}|V_{cb}|=(41.10 pm 1.14)times 10^{-3}$.
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A complete review of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements and of the experimental methods for their determination is presented. A critical analysis of the relevant experimental results, and in particular of the most recent ones, allows to improve the accuracies of all the matrix elements. A chi-square minimization with the three-family unitarity constraint on the CKM matrix is performed to test the current interpretation of the CP violating phenomena inside the Standard Model. A complete and unambiguous solution satisfying all the imposed constraints is found. As a by-product of the fit, the precision on the values of the matrix elements is further increased and it is possible to obtain estimates for the important CP violation observables $sin 2beta$, $sin 2alpha$ and $gamma$. Finally, an independent estimation of the CKM elements based on a Bayesian approach is performed. This complementary method constitutes a check of the results obtained, providing also the probability functions of the CKM elements and of the related quantities.
We present a new measurement of the CKM matrix element $|V_{cb}|$ from $B^{0} to D^{*-} ell^+ u_ell$ decays, reconstructed with the full Belle data set of $711 , rm fb^{-1}$ integrated luminosity. Two form factor parameterizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product $mathcal{F}(1)eta_{rm EW}|V_{cb}|$ and the decay form factors, where $mathcal{F}(1)$ is the normalization factor and $eta_{rm EW}$ is a small electroweak correction. In the CLN parameterization we find $mathcal{F}(1)eta_{rm EW}|V_{cb}| = (35.06 pm 0.15 pm 0.56) times 10^{-3}$, $rho^{2}=1.106 pm 0.031 pm 0.007$, $R_{1}(1)=1.229 pm 0.028 pm 0.009$, $R_{2}(1)=0.852 pm 0.021 pm 0.006$. For the BGL parameterization we obtain $mathcal{F}(1)eta_{rm EW}|V_{cb}|= (34.93 pm 0.23 pm 0.59)times 10^{-3}$, which is consistent with the World Average when correcting for $mathcal{F}(1)eta_{rm EW}$. The branching fraction of $B^{0} to D^{*-} ell^+ u_ell$ is measured to be $mathcal{B}(B^{0}rightarrow D^{*-}ell^{+} u_{ell}) = (4.90 pm 0.02 pm 0.16)%$. We also present a new test of lepton flavor universality violation in semileptonic $B$ decays, $frac{{cal B }(B^0 to D^{*-} e^+ u)}{{cal B }(B^0 to D^{*-} mu^+ u)} = 1.01 pm 0.01 pm 0.03~$. The errors correspond to the statistical and systematic uncertainties respectively. This is the most precise measurement of $mathcal{F}(1)eta_{rm EW}|V_{cb}|$ and form factors to date and the first experimental study of the BGL form factor parameterization in an experimental measurement.
This paper describes a determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ using the decay $B^0to D^{*-}ell^+ u_ell$. We perform a combined measurement of this quantity and of the form factors $rho^2$, $R_1(1)$, and $R_2(1)$ which fully characterize this decay in the framework of heavy-quark effective theory, based on 140 fb$^{-1}$ of Belle data collected near the $Upsilon(4S)$ resonance. The results, based on about 69,000 reconstructed $B^0to D^{*-}ell^+ u_ell$ decays, are $rho^2=1.293pm 0.045pm 0.029$, $R_1(1)=1.495pm 0.050pm 0.062$, $R_2(1)=0.844pm 0.034pm 0.019$ and $mathcal{F}(1)|V_{cb}|=34.4pm 0.2pm 1.0$. The $B^0to D^{*-}ell^+ u_ell$ branching fraction is found to be $(4.42pm 0.03pm 0.25)%$. For all these numbers, the first error is the statistical and the second is the systematic uncertainty. All results are preliminary.
We report branching fraction measurements of the decays $B^+toetaell^+ u_ell$ and $B^+toeta^primeell^+ u_ell$ based on 711~fb$^{-1}$ of data collected near the $Upsilon(4S)$ resonance with the Belle experiment at the KEKB asymmetric-energy $e^+e^-$ collider. This data sample contains 772 million $Bbar B$~events. One of the two $B$~mesons is fully reconstructed in a hadronic decay mode. Among the remaining (signal-$B$) daughters, we search for the $eta$~meson in two decay channels, $etatogammagamma$ and $etatopi^+pi^-pi^0$, and reconstruct the $eta^{prime}$~meson in $eta^primetoetapi^+pi^-$ with subsequent decay of the $eta$ into $gammagamma$. Combining the two $eta$ modes and using an extended maximum likelihood, the $B^+toetaell^+ u_ell$ branching fraction is measured to be $(4.2pm 1.1 (rm stat.)pm 0.3 (rm syst.))times 10^{-5}$. For $B^+toeta^primeell^+ u_ell$, we observe no significant signal and set an upper limit of $0.72times 10^{-4}$ at 90% confidence level.
We present an analysis of the exclusive $B^{+}topi^{+}pi^{-}ell^{+} u_{ell}$ decay, where $ell$ represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The analysis uses the full $Upsilon(4S)$ data sample collected by the Belle detector, corresponding to 711 fb$^{-1}$ of integrated luminosity. We select the events by fully reconstructing one $B$ meson in hadronic decay modes, subsequently determining the properties of the other $B$ meson. We extract the signal yields using a binned maximum-likelihood fit to the missing-mass squared distribution in bins of the invariant mass of the two pions or the momentum transfer squared. We measure a total branching fraction of ${{cal B}(B^{+}to pi^{+}pi^{-}ell^{+} u_{ell})= [22.7 ^{+1.9}_{-1.6} (mathrm{stat}) pm 3.5(mathrm{syst}) ]times 10^{-5}}$, where the uncertainties are statistical and systematic, respectively. This result is the first reported measurement of this decay.
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