Measurements of time-dependent CP asymmetries in B→D∗∓π±B \to D^{*\mp} \pi^{\pm} decays using a partial reconstruction technique

We report results on time-dependent CP asymmetries in $B \to D^{*\mp}\pi^{\pm}$ decays based on a data sample containing 657 {\times} $10^6$ $B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider at the $\Upsilon(4S)$ resonance. We use a partial reconstruction technique, wherein signal $B \to D^{*\mp}\pi^{\pm}$ events are identified using information only from the fast pion from the B decay and the slow pion from the subsequent decay of the $D^{*\mp}$, where the former (latter) corresponds to $D^{*+} (D^{*-})$ final states. We obtain CP violation parameters $S^+ = +0.061 \pm 0.018(\mathrm{stat}) \pm 0.012(\mathrm{syst})$ and $S^- = +0.031 \pm 0.019(\mathrm{stat}) \pm 0.015(\mathrm{syst})$.Comment: 8 pages, 5 figures, 2 tables, submitted to Physical Review D (RC

Evidence of the Purely Leptonic Decay B- --> tau- nu_tau-bar

We present the first evidence of the decay B- --> tau- nu_tau-bar using 414 fb^-1 of data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. Events are tagged by fully reconstructing one of the B mesons in hadronic modes. We detect the signal with a significance of 3.5 standard deviations including systematics, and measure the branching fraction to be Br(B- --> tau- nu_tau-bar) = (1.79 +0.56-0.49(stat) +0.46-0.51(syst))*10^-4. This implies that f_B = 0.229 +0.036-0.031(stat) +0.034-0.037(syst) GeV and is the first direct measurement of this quantity.Comment: 6 pages, 3 figures, to appear in Physical Review Letter

Improved measurement of time-dependent CP violation in B0 -> J/Psi pi0 decays

We report improved measurements of time-dependent CP violation parameters for $B^0(\bar{B}^0) \to J/\psi \pi^0$ decay. This analysis is based on 535 million $B\bar{B}$ pairs accumulated at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. From the distribution of proper time intervals between the two B decays, we obtain the following CP violation parameters $\mathcal{S}_{J/\psi \pi^0} = -0.65\pm0.21 (\rm{stat})\pm0.05 (\rm{syst})$ and $\mathcal{A}_{J/\psi \pi^0} = +0.08\pm0.16 (\rm{stat})\pm0.05 (\rm{syst})$, which are consistent with Standard Model expectations.Comment: Resubmitted to PRD(RC), including 4 figures, 6pages Revision has been made according to communication with PRD referee

Observation of Two Resonant Structures in e+e- to pi+ pi- psi(2S) via Initial State Radiation at Belle

The cross section for e+e- to pi+ pi- psi(2S) between threshold and \sqrt{s}=5.5 GeV is measured using 673 fb^{-1} of data on and off the \Upsilon(4S) resonance collected with the Belle detector at KEKB. Two resonant structures are observed in the pi+ pi- psi(2S) invariant mass distribution, one at 4361\pm 9\pm 9 MeV/c2 with a width of 74\pm 15\pm 10 MeV/c2, and another at 4664\pm 11\pm 5 MeV/c2 with a width of 48\pm 15\pm 3 MeV/c2, if the mass spectrum is parameterized with the coherent sum of two Breit-Wigner functions. These values do not match those of any of the known charmonium states.Comment: 10 pages, 5 figures, 2 tables, version to appear in Phys. Rev. Let

First study of \eta_c, \eta(1760) and X(1835) production via \eta'\pi^+\pi^- final states in two-photon collisions

The invariant mass spectrum of the \eta' \pi^+ \pi^- final state produced in two-photon collisions is obtained using a 673 fb^{-1} data sample collected in the vicinity of the \Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We observe a clear signal of the \eta_c and measure its mass and width to be M(\eta_c)=(2982.7 +- 1.8(stat) +- 2.2(syst) +- 0.3(model)) MeV/c^2 and \Gamma(\eta_c) = (37.8^{+5.8}_{-5.3}(stat) +- 2.8(syst) +- 1.4(model)) MeV/c^2. The third error is an uncertainty due to possible interference between the \eta_c and a non-resonant component. We also report the first evidence for \eta(1760) decay to \eta' \pi^+ \pi^-; we find two solutions for its parameters, depending on the inclusion or not of the X(1835), whose existence is of marginal significance in our data. From a fit to the mass spectrum using coherent X(1835) and \eta(1760) resonant amplitudes, we set a 90% confidence level upper limit on the product \Gamma_{\gamma\gamma} \BR (\eta' \pi^+ \pi^-) for the X(1835).Comment: 13 pages, 7 figures, submitted to PR

Study of B -> D** l nu with full reconstruction tagging

We report a study of semileptonic B decays to P-wave D** mesons. Semileptonic decay to D*_2 meson is observed for the first time and its product branching ratio is measured to be Br(B+ -> anti-D*0_2 l+nu) x Br(anti-D*0_2 -> D- pi+) = 0.22 +- 0.03(stat.) +- 0.04(syst.)%. The result is obtained using the fully reconstructed B tags from a data sample that contains 657 millions BB-bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider.Comment: 12 pages, 4 figures, submitted to PRD(RC

Search for CP violation in the decays D(s)+→KS0π+D^+_{(s)} \to K_S^0\pi^+ and D(s)+→KS0K+D^+_{(s)} \to K_S^0K^+

We have searched for CP violation in the charmed meson decays $D^{+}_{(s)}\to K^0_S\pi^+$ and $D^{+}_{(s)}\to K^0_S K^+$ using 673 fb$^{-1}$ of data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No evidence for CP violation is observed. We report the most sensitive CP asymmetry measurements to date for these decays: $A_{CP}^{D^+\to K^0_S\pi^+}=(-0.71\pm0.19\pm0.20)$, $A_{CP}^{D^+_s\to K^0_S\pi^+}=(+5.45\pm2.50\pm0.33)$, $A_{CP}^{D^+\to K^0_S K^+}=(-0.16\pm0.58\pm0.25)$, and $A_{CP}^{D^+_s\to K^0_S K^+}=(+0.12\pm0.36\pm0.22)$, where the first uncertainties are statistical and the second are systematic

Measurement of the decay B0→π−ℓ+νB^0\to\pi^-\ell^+\nu and determination of ∣Vub∣|V_{ub}|

We present a measurement of the charmless semileptonic decay $B^0\to\pi^-\ell^+\nu$ using a data sample containing 657$\times 10^6$ $B\bar{B}$ 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, $\mathcal{B}(B^0\to\pi^-\ell^+\nu)=(1.49\pm 0.04{(\mathrm{stat})}\pm 0.07{(\mathrm{syst})})\times 10^{-4}$. 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 $|V_{ub}|=(3.43\pm 0.33)\times 10^{-3}$, where the error includes both statistical and systematic uncertainties.Comment: 8 pages, 3 figures, Submitted to PRD(RC

Search for leptonic decays of D0 mesons

We search for the flavor-changing neutral current decays D0\to mu+mu- and D0\to e+e-, and for the lepton-flavor violating decays D0\to e\pm mu\mp using 660 fb^-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We find no evidence for any of these decays. We obtain significantly improved upper limits on the branching fractions: B(D0\to mu+mu-)<1.4x10-7, B(D0\to e+e-)<7.9x10-8, and B(D0\to e+mu-)+B(D0\to mu+e-)<2.6x10-7 at 90% confidence level.Comment: 6 pages, 3 figure

Search for CP violation in tau -> K^0_S pi nu_tau decays at Belle

We report on a search for CP violation in tau -> K^0_S pi nu_tau decays using a data sample of 699 fb^{-1} collected in the Belle experiment at the KEKB electron-positron asymmetric-energy collider. The CP asymmetry is measured in four bins of the invariant mass of the K^0_S pi system and found to be compatible with zero with a precision of O(10^{-3}) in each mass bin. Limits for the CP violation parameter Im(eta_S) are given at a 90 % confidence level. These limits are |Im(eta_S)|<0.026 or better, depending on the parameterization used to describe the hadronic form factors and improve upon previous limits by one order of magnitude