Measurement of D0-D0bar mixing and search for CP violation in D0 -> K+K-, pi+pi- decays with the full Belle data set

We report an improved measurement of D0-D0bar mixing and a search for CP violation in D0 decays to CP-even final states K+K- and pi+pi-. The measurement is based on the final Belle data sample of 976/fb. The results are y_CP=(1.11 +- 0.22 +- 0.09)% and A_Gamma=(-0.03 +- 0.20 +- 0.07)%, where the first uncertainty is statistical and the second is systematic.Comment: 8 pages, 5 figures; submitted to Phys. Lett.

Study of X(3872) in BB meson decays

We present results on the X(3872), produced in $B^+ \to X(3872) K^+$ and $B^0 \to X(3872) K^0_S$ decays where $X(3872) \to J/\psi \pi^+ \pi^-$. We report the first statistically significant observation of $B^0 \to X(3872) K^0_S$ and measure the ratio of branching fractions to be $\frac{{\cal B}(B^0 \to X(3872)K^0)} {{\cal B}(B^+ \to X(3872)K^+)} = 0.82 \pm 0.22 \pm 0.05$, consistent with unity. The mass difference between the X(3872) states produced in $B^+$ and $B^0$ decay is found to be $\delta M \equiv M_{XK^+} - M_{XK^0} = (+0.18 \pm 0.89 \pm 0.26)$ MeV/$c^2$, consistent with zero. In addition, we search for the X(3872) in the decay $B^0 \to X(3872)K^+\pi^-$, $X(3872) \to J/\psi \pi^+ \pi^-$. We measure ${\cal B}(B^0 \to X(3872) (K^+ \pi^-)_{NR}) \times {\cal B}(X(3872) \to J/\psi \pi^+ \pi^-) = (8.1 \pm 2.0 ^{+1.1}_{-1.4})\times 10^{-6}$ and we set the 90% C.L. limit, ${\cal B}(B^0 \to X(3872)K^{*}(892)^0) \times {\cal B}(X(3872) \to J/\psi \pi^+ \pi^-) < 3.4 \times 10^{-6}$. The analysis is based on a 605 fb$^{-1}$ data sample collected at the $\Upsilon(4S)$ with the Belle detector at the KEKB collider.Comment: 10 pages, 5 figures, Contributed to the 34th International Conference On High Energy Physics (ICHEP 2008

Hadronic Mass Moments in B -> X_c l nu Decays

We report measurements of the first and second moments of the hadronic invariant mass squared distribution, and )^2>, in B -> X_c l nu decays for minimum lepton momenta ranging from 0.7 to 1.5 GeV/c in the B meson rest frame. The measurement uses BBbar events in which the hadronic decay of one B meson is fully reconstructed and the semileptonic decay of the other B is inferred from the presence of an identified lepton. These results are obtained from a 140 fb^-1 data sample collected near the Y(4S) resonance with the Belle detector at the KEKB asymmetric energy e^+e^- collider.Comment: 9 pages, 2 figures, 4 tables, contributed to Lepton Photon and EPS 200

Moments of the Electron Energy Spectrum in B --> X_c l \nu decays at Belle

We report a measurement of the inclusive electron energy spectrum for charmed semileptonic decays of B mesons in a 140 fb^-1 data sample collected on the Upsilon(4S) resonance, with the Belle detector at the KEKB asymmetric energy e^+ e^- collider. We determine the first, second and third moments of the electron energy spectrum for threshold values of the electron energy between 0.4 and 1.5 GeV.Comment: 13 pages, 3 figures, 6 tables, contributed to HEP2005 International Europhysics Conference on High Energy Physic

Measurement of D0 -> pilnu (Klnu) and their form factors

Using a data sample of 282 1/fb collected by the Belle experiment at the KEKB e+e- collider, we study D0 -> pilnu and D0 -> Klnu decays (l = mu,e) in e+e- annihilation. We identify D* -> D0pi decays by using the mass of the system recoiling against a fully reconstructed tag-side D* or D meson, allowing for additional primary mesons from fragmentation. Using a novel global reconstruction method that provides very good resolution in neutrino momentum and in q^2 = (p_l+p_nu)^2, we reconstructed D0 -> pilnu and D0 -> Klnu decays. From these events we measured the branching fraction ratios BR(D0 -> pienu)/BR(D0 -> Kenu) = 0.0809 +- 0.0080 +- 0.0032$ and BR(D0 -> pimunu)/BR(D0 -> Kmunu) = 0.0677 +- 0.0078 +- 0.0047, and the semileptonic form factor ratio f+(D0 -> pilnu})^2/f+(D0 -> Klnu})^2|Vcd|^2/|Vcs|^2|_{q^2=0} = 0.041 +- 0.003 +- 0.004, where the errors are statistical and systematic, respectively.Comment: 20 pages, 8 figures; corrected form factor rati

Moments of the Hadronic Mass Spectrum in Inclusive Semileptonic B Decays at Belle

We report a measurement of the first and second moment of the hadronic mass distribution M_X in B -> X_c l nu decays for lepton threshold momenta ranging from 0.9 to 1.6 GeV/c in the center of mass frame. The measurement uses B Bbar events in which the hadronic decay of one B meson is fully reconstructed and a charged lepton from the decay of the other B meson is identified. These results are obtained from a 140 fb^-1 data sample collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e^+ e^- collider.Comment: 9 pages, 3 figures, submitted to ICHEP2004, Beijing, Chin

Study of the Y (4260) resonance in e+e- collisions with initial state radiation at Belle

We present a study of Y(4260) properties using the initial-state radiation process e^+e^- -> gamma_{ISR} Y(4260). The Y(4260) resonance is reconstructed in the pi^+ pi^- J/\psi decay mode, using data collected by the Belle detector at the KEKB e^+e^- collider. We find a significant signal with a central mass value of (4295 +-10 +10 -3) MeV/c^2 and a width of (133 +-26 +13 -6) MeV/c^2. We find Gamma_{ee}.B(Y(4260) -> pi^+ pi^- J/\psi) = (8.7 +- 1.1 +0.3 -0.9) eV. These results are preliminary.Comment: 15 pages, 11 figures, shown at ICHEP 0

Improved Measurement of the Electroweak Penguin Process B->Xsll

We present an improved measurement of the branching fraction for the electroweak penguin process B->Xsl+l-, where l is an electron or a muon and Xs is a hadronic system containing an s-quark. The measurement is based on a sample of 152 * 10^6 ~ Upsilon(4S) -> BB-bar events collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. The Xs hadronic system is reconstructed from one K+- or K0s and up to four pions, where at most one pion can be neutral. Summing over both lepton flavors, the inclusive branching fraction is measured to be Br(B->Xsll)=(4.11 +- 0.83(stat.) +0.74 -0.70 (syst.) )*10^{-6} for m(ll) > 0.2GeV.Comment: 22 pages, 5 figures, submitted to ICHEP2004, Beijing, Chin

Observation of the decay Bs0→J/ψηB_s^0\to J/\psi\eta and Evidence for Bs0→J/ψη′B_s^0\to J/\psi\eta'

We report the first observation of $B_s^0\to J/\psi\eta$ and evidence for $B_s^0\to J/\psi\eta'$. These results are obtained from $23.6 \mathrm{fb}^{-1}$ of data collected at the $\Upsilon(5S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We measure the branching fractions \mathcal{B}(B_s^0\to J/\psi\eta)= (3.32 \pm 0.87(\mathrm{stat.})^{+0.32}_{-0.28}(\mathrm{syst.}) \pm 0.42(f_s))\times 10^{-4}} with a significance of $7.3 \sigma$, and $\mathcal{B}(B_s^0\to J/\psi\eta')= (3.1 \pm 1.2(\mathrm{stat.})^{+0.5}_{-0.6}(\mathrm{syst.}) \pm 0.38(f_s))\times 10^{-4}$ with a significance of $3.8 \sigma$.Comment: 6 pages, 3 figures, 2 tables. Contributed to Moriond QCD 09, FPCP 09, EPS HEP 09, DPF 09, and BEAUTY 0

Measurement of the form factors of the decay B^+\to\bar D^{*0}\ell^+\nu_\ell and determination of the CKM matrix element |V_{cb}|

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ times the form factor normalization $\mathcal{F}(1)$ using the decay $B^+\to\bar D^{*0}\ell^+\nu_\ell$. This measurement is performed together with a determination of the form factor parameters $\rho^2$, $R_1(1)$ and $R_2(1)$ which fully characterize this decay in the framework of Heavy Quark Effective Theory. This analysis is based on a data sample equivalent to 140 fb$^{-1}$ of Belle data collected near the $\Upsilon(4S)$ resonance. The preliminary results, based on about 27,000 reconstructed $B^+\to\bar D^{*0}\ell^+\nu_\ell$ decays, are $\rho^2=1.376\pm 0.074\pm 0.056$, $R_1(1)=1.620\pm 0.091\pm 0.092$, $R_2(1)=0.805\pm 0.064\pm 0.036$ and $\mathcal{F}(1)|V_{cb}|=35.0\pm 0.4\pm 2.2$. We find the $B^+\to\bar D^{*0}\ell^+\nu_\ell$ branching fraction to be $(4.84\pm 0.04\pm 0.56)$. For all numbers quoted here, the first error is the statistical and the second is the systematic uncertainty. A direct, model-independent determination of the form factor shapes has also been carried out and shows good agreement with the HQET based form factor parametrization by Caprini {\it et al.}.Comment: 22 pages, 8 figure