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Register a new userMeasurement of the decay $B^0topi^-ell^+ u$ and determination of $|V_{ub}|$
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We present a measurement of the charmless semileptonic decay $B^0topi^-ell^+ u$ using a data sample containing 657$times 10^6$ $Bbar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider operating near the $Upsilon(4S)$ resonance. We determine the total branching fraction of the decay, $mathcal{B}(B^0topi^-ell^+ u)=(1.49pm 0.04{(mathrm{stat})}pm 0.07{(mathrm{syst})})times 10^{-4}$. We also report a new precise measurement of the differential decay rate, and extract the Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ using model-independent and -dependent approaches. From a simultaneous fit to the measured differential decay rate and lattice QCD results, we obtain $|V_{ub}|=(3.43pm 0.33)times 10^{-3}$, where the error includes both statistical and systematic uncertainties.
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We reassess the $Btopiell u_{ell}$ differential branching ratio distribution experimental data released by the BaBar and Belle Collaborations supplemented with all lattice calculations of the $Btopi$ form factor shape available up to date obtained by the HPQCD, FNAL/MILC and RBC/UKQCD Collaborations. Our study is based on the method of Pad{e} approximants, and includes a detailed scrutiny of each individual data set that allow us to obtain $|V_{ub}|=3.53(8)_{rm{stat}}(6)_{rm{syst}}times10^{-3}$. The semileptonic $B^{+}toeta^{(prime)}ell^{+} u_{ell}$ decays are also addressed and the $eta$-$eta^{prime}$ mixing discussed.
B --> rho l nu decay is analyzed in the effective theory of heavy quark with infinite mass limit. The matrix element relevant to the heavy to light vector meson semileptonic decays is parametrized by a set of four heavy flavor-spin independent universal wave functions at the leading order of effective theory. The form factors are calculated at the leading 1/m_Q order using the light cone sum rule method in the framework of effective theory. |V_{ub}| is then extracted via B --> rho l nu decay mode.
We investigate $ovar{B^0} to D_s^- pi^+$ decay in perturbative QCD approach which has recently been applied to $B$ meson decays. $ovar{B^0} to D_s^- pi^+$ decay (and its charge conjugated mode) can be one of the hopeful modes to determine $|V_{ub}|$ since it occurs through $b to u$ transition only. We estimate both factorizable and non-factorizable contribution, and show that the non-factorizable contribution is much less than the factorizable one. Our calculation gives ${BR}(ovar{B^0} to D_s^- pi^+) = (50 sim 70) times f_{Ds}^2|{V_{ub}}{V_{cs}}|^2$.
The first observation of the suppressed semileptonic $B_s^0 to K^-mu^+ u_mu$ decay is reported. Using a data sample recorded in {it pp} collisions in 2012 with the LHCb detector, corresponding to an integrated luminosity of 2 $mathrm{fb}^{-1}$, the branching fraction mbox{$mathcal{B}(B_s^0 to K^-mu^+ u_mu)$} is measured to be $(1.06pm0.05~(mathrm{stat})pm0.08~(mathrm{syst}))times 10^{-4}$, where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. The decay $B_s^0 to D_s^-mu^+ u_mu$, where $D_s^-$ is reconstructed in the final state $K^+K^-pi^-$, is used as a normalization channel to minimize the experimental systematic uncertainty. Theoretical calculations on the form factors of the $B_s^0 to K^-$ and $B_s^0 to D_s^-$ transitions are employed to determine the ratio of the CKM matrix elements ${|V_{ub}|}/{|V_{cb}|}$ at low and high $B_s^0 to K^-$ momentum transfer.
We present a lattice quantum chromodynamics determination of the ratio of the scalar and vector form factors for two semileptonic decays of the $B_s$ meson: $B_s rightarrow K ell u$ and $B_s rightarrow D_s ell u$. In conjunction with future experimental data, our results for these correlated form factors will provide a new method to extract $|V_{ub}/V_{cb}|$, which may elucidate the current tension between exclusive and inclusive determinations of these Cabibbo-Kobayashi-Maskawa mixing matrix parameters. In addition to the form factor results, we determine the ratio of the differential decay rates, and forward-backward and polarization asymmetries, for the two decays.
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