The precise determination of the CKM matrix element $\left| V_{cb}\right|$ is important for carrying out tests of the flavour sector of the Standard Model. In this article we present a preliminary analysis of the $\bar B^0 \to D^{*\,+} \, \ell^- \, \bar \nu_\ell$ decay mode and its charge conjugate, selected in events that contain a fully reconstructed $B$-meson, using 772 million $e^+ \, e^- \to \Upsilon(4S) \to B \bar B$ events recorded by the Belle detector at KEKB. Unfolded differential decay rates of four kinematic variables fully describing the $\bar B^0 \to D^{*\,+} \, \ell^- \, \bar \nu_\ell$ decay in the $B$-meson rest frame are presented. We measure the total branching fraction $\mathcal{B}( \bar B^0 \to D^{*\,+} \, \ell^- \, \bar \nu_\ell ) = \left(4.95 \pm 0.11 \pm 0.22 \right) \times 10^{-2}$, where the errors are statistical and systematic respectively. The value of $\left|V_{cb} \right|$ is determined to be $\left( 37.4 \pm 1.3 \right) \times 10^{-3}$. Both results are in good agreement with current world averages.
The unfolded differential rate as a function of $w$.
The unfolded differential rate as a function of $\cos\theta_\nu$.
The unfolded differential rate as a function of $\cos\theta_\ell$.
We report a study of radiative decays of \chi_{bJ}(1P)(J=0,1,2) mesons into 74 hadronic final states comprising charged and neutral pions, kaons, protons; out of these, 41 modes are observed with at least 5 standard deviation significance. Our measurements not only improve the previous measurements by the CLEO Collaboration but also lead to first observations in many new modes. The large sample allows us to probe the total decay width of the \chi_{b0}(1P). In the absence of a statistically significant result, a 90% confidence-level upper limit is set on the width at \Gamma_{total}< 2.4 MeV. Our results are based on 24.7 fb^{-1} of e+e- collision data recorded by the Belle detector at the \Upsilon(2S) resonance, corresponding to (157.8\pm3.6)\times10^6 \Upsilon(2S) decays.
Product branching fractions ${\cal B}[\Upsilon(2S)\to\gamma\chi_{b0}(1P)]\times{\cal B}[\chi_{b1}(1P)\to h_{i}]$ ($\times 10^{-5}$) and statistical significance for $\chi_{b0}(1P)$ state. Upper limits at the 90% CL are calculated for modes having significance less than 3$\sigma$.
Product branching fractions ${\cal B}[\Upsilon(2S)\to\gamma\chi_{b1}(1P)]\times{\cal B}[\chi_{b1}(1P)\to h_{i}]$ ($\times 10^{-5}$) and statistical significance for $\chi_{b1}(1P)$ state. Upper limits at the 90% CL are calculated for modes having significance less than 3$\sigma$.
Product branching fractions ${\cal B}[\Upsilon(2S)\to\gamma\chi_{b2}(1P)]\times{\cal B}[\chi_{b1}(1P)\to h_{i}]$ ($\times 10^{-5}$) and statistical significance for $\chi_{b2}(1P)$ state. Upper limits at the 90% CL are calculated for modes having significance less than 3$\sigma$.
We present a measurement of angular observables, $P_4'$, $P_5'$, $P_6'$, $P_8'$, in the decay $B^0 \to K^\ast(892)^0 \ell^+ \ell^-$, where $\ell^+\ell^-$ is either $e^+e^-$ or $\mu^+\mu^-$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711~\mathrm{fb}^{-1}$ containing $772\times 10^{6}$ $B\bar B$ pairs, collected at the $\Upsilon(4S)$ resonance with the Belle detector at the asymmetric-energy $e^+e^-$ collider KEKB. Four angular observables, $P_{4,5,6,8}'$ are extracted in five bins of the invariant mass squared of the lepton system, $q^2$. We compare our results for $P_{4,5,6,8}'$ with Standard Model predictions including the $q^2$ region in which the LHCb collaboration reported the so-called $P_5'$ anomaly.
Results of the angular analysis of $B^0 \to K^\ast(892)^0 \ell^+ \ell^-$ (where $\ell = e,\mu$) in five bins of $q^2$, the di-lepton invariant mass squared.
We report a measurement of the differential cross section of $\pi^0$ pair production in single-tag two-photon collisions, $\gamma^* \gamma \to \pi^0 \pi^0$, in $e^+ e^-$ scattering. The cross section is measured for $Q^2$ up to 30 GeV$^2$, where $Q^2$ is the negative of the invariant mass squared of the tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and $|\cos \theta^*|$ < 1.0 for the total energy and pion scattering angle, respectively, in the $\gamma^* \gamma$ center-of-mass system. The results are based on a data sample of 759 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The transition form factor of the $f_0(980)$ and that of the $f_2(1270)$ with the helicity-0, -1, and -2 components separately are measured for the first time and are compared with theoretical calculations.
$W$ dependence of the differential cross section ${\rm d}\sigma/{\rm d}|\cos\theta^*|$ in five $|\cos\theta^*|$ bins for $Q^2$=3.45 GeV$^2$.
$W$ dependence of the differential cross section ${\rm d}\sigma/{\rm d}|\cos\theta^*|$ in five $|\cos\theta^*|$ bins for $Q^2$=4.46 GeV$^2$.
$W$ dependence of the differential cross section ${\rm d}\sigma/{\rm d}|\cos\theta^*|$ in five $|\cos\theta^*|$ bins for $Q^2$=5.47 GeV$^2$.
Using data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we measure the energy dependence of the $e^+e^- \to h_b(nP)\pi^+\pi^-$ $(n=1,2)$ cross sections from thresholds up to $11.02\,$GeV. We find clear $\Upsilon(10860)$ and $\Upsilon(11020)$ peaks with little or no continuum contribution. We study the resonant substructure of the $\Upsilon(11020) \to h_b(nP)\pi^+\pi^-$ transitions and find evidence that they proceed entirely via the intermediate isovector states $Z_b(10610)$ and $Z_b(10650)$. The relative fraction of these states is loosely constrained by the current data: the hypothesis that only $Z_b(10610)$ is produced is excluded at the level of 3.3 standard deviations, while the hypothesis that only $Z_b(10650)$ is produced is not excluded at a significant level.
Center-of-mass energies, integrated luminosities and Born cross sections for all energy points. The first uncertainty in the energy is uncorrelated, the second is correlated. The three uncertainties in the cross sections are statistical, uncorrelated systematic and correlated systematic.
We report the first measurement of the lepton forward-backward asymmetry ${\cal A}_{\rm FB}$ as a function of the squared four-momentum of the dilepton system, $q^2$, for the electroweak penguin process $B \rightarrow X_s \ell^+ \ell^-$ with a sum of exclusive final states, where $\ell$ is an electron or a muon and $X_s$ is a hadronic recoil system with an $s$ quark. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ pairs recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. ${\cal A}_{\rm FB}$ for the inclusive $B \rightarrow X_s \ell^+ \ell^-$ is extrapolated from the sum of 10 exclusive $X_s$ states whose invariant mass is less than 2 GeV/$c^2$. For $q^2 > 10.2$ GeV$^2$/$c^2$, ${\cal A}_{\rm FB} < 0$ is excluded at the 2.3$\sigma$ level, where $\sigma$ is the standard deviation. For $q^2 < 4.3$ GeV$^2$/$c^2$, the result is within 1.8$\sigma$ of the Standard Model theoretical expectation.
The value of ASYM(FB) obtained from the fit in each of the four Q**2 bins.
We report a high-statistics measurement of the differential cross section of the process gamma gamma --> K^0_S K^0_S in the range 1.05 GeV <= W <= 4.00 GeV, where W is the center-of-mass energy of the colliding photons, using 972 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider operated at and near the Upsilon-resonance region. The differential cross section is fitted by parameterized S-, D_0-, D_2-, G_0- and G_2-wave amplitudes. In the D_2 wave, the f_2(1270), a_2(1320) and f_2'(1525) are dominant and a resonance, the f_2(2200), is also present. The f_0(1710) and possibly the f_0(2500) are seen in the S wave. The mass, total width and product of the two-photon partial decay width and decay branching fraction to the K bar{K} state Gamma_{gamma gamma}B(K bar{K}) are extracted for the f_2'(1525), f_0(1710), f_2(2200) and f_0(2500). The destructive interference between the f_2(1270) and a_2(1320) is confirmed by measuring their relative phase. The parameters of the charmonium states chi_{c0} and chi_{c2} are updated. Possible contributions from the chi_{c0}(2P) and chi_{c2}(2P) states are discussed. A new upper limit for the branching fraction of the P- and CP-violating decay channel eta_c --> K^0_S K^0_S is reported. The detailed behavior of the cross section is updated and compared with QCD-based calculations.
The W dependence of the cross section after integrating up to |cosTheta*|<0.8 and 0.6.
The cos(Theta*) dependence of the differential cross section for the W ranges 1.10-1.11, 1.11-1.12 and 1.12-1.13.
The cos(Theta*) dependence of the differential cross section for the W ranges 1.13-1.14, 1.14-1.15 and 1.15-1.16.
Measurements of inclusive differential cross sections for charged pion and kaon production in electron-positron annihilation have been carried out at a center-of-mass energy of Q = 10.52 GeV. The measurements were performed with the Belle detector at the KEKB electron-positron collider using a data sample containing 113 million e+e- -> qqbar events, where q={u,d,s,c}. We present charge-integrated differential cross sections d\sigma_h+-/dz for h+- = pi+-, K+- as a function of the relative hadron energy z = 2*E_h / sqrt{s} from 0.2 to 0.98. The combined statistical and systematic uncertainties for pi+- (K+-) are 4% (4%) at z ~ 0.6 and 15% (24%) at z ~ 0.9. The cross sections are the first measurements of the z-dependence of pion and kaon production for z > 0.7 as well as the first precision cross section measurements at a center-of-mass energy far below the Z^0 resonance used by the experiments at LEP and SLC.
Measured charged-integrated differential cross sections for charged pion and kaon production as a function of the fractional hadron energy Z (=2*Eh/sqrt(s)).
This article describes a determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ from the decay $B^0\to D^{*-}\ell^+\nu_\ell$ using 711 fb$^{-1}$ of Belle data collected near the $\Upsilon(4S)$ resonance. We simultaneously measure the product of the form factor normalization $\mathcal{F}(1)$ and the matrix element $|V_{cb}|$ as well as the three parameters $\rho^2$, $R_1(1)$ and $R_2(1)$, which determine the form factors of this decay in the framework of the Heavy Quark Effective Theory. The results, based on about 120,000 reconstructed $B^0\to D^{*-}\ell^+\nu_\ell$ decays, are $\rho^2=1.214\pm 0.034\pm 0.009$, $R_1(1)=1.401\pm 0.034\pm 0.018$, $R_2(1)=0.864\pm 0.024\pm 0.008$ and $\mathcal{F}(1)|V_{cb}|=(34.6\pm 0.2\pm 1.0)\times 10^{-3}$. The branching fraction of $B^0\to D^{*-}\ell^+\nu_\ell$ is measured at the same time/ we obtain a value of $\mathcal{B}(B^0 \to D^{*-}\ell^+ \nu_\ell) = (4.58 \pm 0.03 \pm 0.26) %$. The errors correspond to the statistical and systematic uncertainties. These results give the most precise determination of the form factor parameters and $\mathcal{F}(1)|V_{cb}|$ to date. In addition, a direct, model-independent determination of the form factor shapes has been carried out.
Continuum-subtracted on-resonance data as a function of the $w$ kinematic variable.
Continuum-subtracted on-resonance data as a function of the $\cos\theta_\ell$ variable.
Continuum-subtracted on-resonance data as a function of the $\cos\theta_\nu$ variable.
We present a study of differential two jet ratios in multi-hadronic final states produced by e + e − annihilation in the AMY detector at TRISTAN. The data are compared to the predictions of the next-to-leading logarithm parton-shower (NLL PS) Monte Carlo and the O ( α s 2 ) matrix element QCD models. We determine the strong coupling strength α s (57.3 GeV) = 0.130 ± 0.006.
The data are compared to the predictions of Monte-Carlo.
Using the p-scheme for jet clustering.
Using the E-scheme for jet clustering.
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