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Publications and source records attributed to Belle Collaboration.
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.
We report preliminary measurements of the first (mean) and second moment (variance) of the inclusive photon energy spectrum in $B\to X_sγ$ decays, for threshold values of the photon energy in the range 1.8--2.3 GeV as measured in the rest frame of the $B$-meson. These results are obtained from the Belle measurement of the spectrum, which used a data set consisting of 152 million $B\bar{B}$ pairs collected by the Belle detector at the KEKB asymmetric-energy electron-positron collider operated on the $Υ(4S)$ resonance.
We report a new measurement of the branching fraction of neutral $B$ meson decays $B^0\ra a_{1}^{\pm}(1260)π^{\mp}$ with \ensuremath{a_{1}^{\pm}(1260)\ra ρ^{0}π^{\pm}} and $ρ^0\ra pi^+π^-$ using $275\times 10^{6}$ BBar pairs collected by the Belle detector at the KEKBasymmetric-energy $e^{+}e^{-}$ collider. We measure the branching fraction $\mathcal{B}($B^0\ra a_{1}^{\pm}(1260)π^{\mp}=(48.6\pm 4.1(stat)\pm 3.9(syst)) \times 10^{-6}$. Using a relativistic Breit-Wigner parameterization, we measure the mass and width of the $a_{1}(1260)$ to be $m_{a_1}=1197\pm 34 MeV/c^2$ and $Γ_{a_1}=305\pm 43 MeV/c^2$, respectively.
We present a new measurement of the time-dependent CP-violating parameters in B0 --> pi+ pi- decays with 275 x 10^6 BB-bar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider operating at the Upsilon(4S) resonance. We find 666 +/- 43 B0 --> pi+ pi- events and measure the CP-violating parameters: S_pipi = -0.67 +/- 0.16(stat) +/- 0.06(syst) and A_pipi = +0.56 +/- 0.12(stat) +/- 0.06(syst). We find evidence for large direct CP-violation with a significance greater than 4 standard deviations for any S_pipi value. Using isospin relations, we obtain 95.4% confidence intervals for the CKM angle phi_2 of 0 deg. < phi_2 < 19 deg. and 71 deg. < phi_2 < 180 deg.
We present a measurement of the unitarity triangle angle phi_3 using a Dalitz plot analysis of the three-body decay of the neutral D meson from the B->D(*)K process. Using a 253 fb-1 data sample collected by the Belle experiment, we obtain 276 signal candidates for B->DK and 69 candidates for B->D*K, where the neutral D meson decays into K_Spi+pi-. From a combined maximum likelihood fit to the B->DK and B->D*K modes, we obtain phi_3=68+14-15(stat)+-13(syst)+-11(model). The corresponding two standard deviation interval is 22<phi_3<113.
An angular analysis for B decays into two vector mesons gives parameters sensitive to new physics. They are the decay amplitudes of the three helicity states, the asymmetry in triple product, and the CP violating phase. The measurements of these quantities are performed for $B^0 \to J/ψK^{*0}$ decays in a data sample with 253 fb$^{-1}$ taken by the Belle detector in the KEKB asymmetric $e^+e^-$ collider. With the time-integrated angular analysis, the decay amplitudes' moduli and phase angles are measured to be $|A_0|^2=0.585\pm 0.012 \pm 0.09$, $|A_{\parallel}|^2=0.233\pm 0.013\pm 0.008$, $|A_\perp|^2=0.181\pm 0.012\pm 0.008$, $\arg(A_\parallel)=2.888\pm 0.090\pm 0.008$ radians, and $\arg(A_\perp)=0.239\pm 0.064\pm 0.010$ radians. The difference between $\arg(A_\parallel)$ and $\arg(A_\perp)$ is $2.649\pm0.110$ radians, which is shifted from $π$ by more than $4σ$; this can be interpreted as evidence for the existence of the final state interaction. The amplitude values are used in triple product correlations to obtainasymmetries of $A_T^{(1)}=0.101\pm 0.033\pm 0.007$ and $A_T^{(2)}=-0.102\pm 0.032\pm 0.003$ for $B^0$ meson decays, and $\bar{A}_T^{(1)}=0.056\pm 0.030\pm 0.006$ and $\bar{A}_T^{(2)} = -0.091\pm 0.028\pm 0.003$ for $\bar{B^0}$ meson decays. The time dependent angular analysis gives the measurements of CP violating parameters $\sin 2ϕ_1$ and $\cos 2ϕ_1$ to be $0.30 \pm 0.32 \pm 0.02$ and $-0.31 \pm 0.91 \pm 0.10$, respectively. The value of $\cos 2ϕ_1$ is $-0.56 \pm 0.86 \pm 0.11$ if $\sin 2ϕ_1$ is fixed at the world average value (0.731).
We present preliminary improved measurements of the branching fractions of the color-suppressed decays B0bar -> D0 h0, where h0 represents the three light neutral mesons pi0, eta and omega. The measurements are based on a data sample of 140fb-1 collected at the Upsilon(4S) with the Belle detector at the KEKB energy-asymmetric e+e- collider, corresponding to seven times the luminosity of the previous Belle measurements.
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.
We present a measurement of the unitarity triangle angle phi_3 using a Dalitz plot analysis of the three-body decay of the neutral D meson from the B->D(*)K process. The method employs the interference between D0 and D0bar to extract both the weak and strong phases. We apply this method to a 140 fb^{-1} data sample collected by the Belle experiment. The analysis uses the modes B->DK and B->D*K, D*->D pi0, where the neutral D meson decays into K_Spi+pi-. We obtain 146 signal candidates for B->DK and 39 candidates for B->D*K. From a combined maximum likelihood fit to the B->DK and B->D*K modes, we obtain phi_3=77^{\circ}^{+17}_{-19}(stat)+-13^{\circ}(syst)}+-11^{\circ}(model). The corresponding two standard deviation interval is 26^{\circ}<phi_3<126^{\circ}.
In this paper we report the first measurement of $e^+e^- \to D^{(*)+}D^{(*)-}$ processes. The cross-sections for $e^+^e- \to D^{*+}D^{*-}$ and $e^+e^- \to D^+D^{*-}$ at $\sqrt{s}=10.58\mathrm{GeV}/c^2$ have been measured to be $0.65 \pm 0.04 \pm 0.07 \mathrm{pb}$ and $0.71 \pm 0.05 \pm 0.09 \mathrm{pb}$, respectively. We set an upper limit on the cross-section of e+e- --> D+ D- of $0.04 \mathrm{pb}$ at the 90% confidence level. In addition we have measured the fraction of the $D^{*\pm}_T D^{*\mp}_L$ final state in the e+e- --> D*+ D*- reaction to be $(97\pm 5)%$. The analysis is performed using $88.9 \mathrm{fb}^{-1}$ of data collected by the Belle detector at the $e^{+}e^{-}$ asymmetric collider KEKB.
A new method to measure the angle $ϕ_3$ of the CKM unitarity triangle using a Dalitz analysis of the three-body decay of the $D^0$ meson from the $B\to D^0 K$ process has been introduced recently. The method employs the interference between $D^0$ and $\bar{D^0}$ to extract both the weak and strong phases. We present a study of statistical and systematic errors of this method using Monte Carlo simulation. A fit of the $D^0$ Dalitz distribution has been performed based on a 140 fb$^{-1}$ sample collected by the Belle detector. We observe the indication of a CP asymmetry with the significance of 2.4 standard deviations. The 90% confidence interval obtained for the $ϕ_3$ value is $61^{\circ}<ϕ_3<142^{\circ}$.
We have searched for the decay B^+ -> omega l^+ nu in 78 fb^-1 of Y(4S) data (85.0 million BBbar events) accumulated with the Belle detector. The final state is fully reconstructed using the omega decay into pi^+ pi^- pi^0 and detector hermeticity to estimate the neutrino momentum. 155 +/- 47 signal events are found in the data, corresponding to a branching fraction of (1.3 +/- 0.4 +/- 0.2 +/- 0.3) x 10^-4, where the first two errors are statistical and systematic. The third error is due to the estimated form-factor uncertainty. (This result is preliminary.)
We report the results of a study of charged B decays to the D+- pi-+ pi-+ and D*+- pi-+ pi-+ final states using complete D(*) reconstruction. The contributions of two-body B => D** pi decays with narrow (j=3/2) and broad (j=1/2) D** states have been determined and the masses and widths of four D** states have been measured. This is the first observation of the broad D*0_0 and D'0_1 mesons. The analysis is based on a data sample of 65 million B barB pairs collected in the Belle experiment.
Using a data sample of 101.8 fb collected by the Belle detector at the KEKB asymmetric energy e+ e- collider, we confirm our published observation of e+ e- -> J/psi eta_c and find no evidence for the process e+ e- -> J/psi J/psi. The latter process was suggested as means to explain the large discrepancy between the published Belle result and theoretical predictions.
We present an improved measurement of CP-violating asymmetries in B0 -> pi+ pi- decays based on a 78 fb^-1 data sample collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct one neutral B meson as a B0 -> pi+ pi- CP eigenstate and identify the flavor of the accompanying B meson from inclusive properties of its decay products. We apply an unbinned maximum likelihood fit to the distribution of the time intervals between the two B meson decay points. The fit yields the CP-violating asymmetry amplitudes Apipi = +0.77+/-0.27(stat)+/-0.08(syst) and Spipi = -1.23+/-0.41(stat)+0.08/-0.07(syst), where the statistical uncertainties are determined from Monte Carlo pseudo-experiments. We obtain confidence intervals for CP-violating asymmetry parameters Apipi and Spipi based on a frequentist approach. We rule out the CP-conserving case, Apipi=Spipi=0, at the 99.93% confidence level. We discuss how these results constrain the value of the CKM angle phi2.
We report the first measurement of the branching fraction for the inclusive decay B --> X(s) l+ l-, where l is either an electron or a muon and X(s) is a hadronic recoil system that contains an s-quark. We analyzed a data sample of 65.4 * 10**6 B meson pairs collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. We find Br(B --> X(s) l+ l-) = (6.1 +/-1.4(stat) +1.4-1.1(syst)) * 10**(-6) for dilepton masses greater than 0.2 GeV/c**2.
We present a measurement of the B^0-B^0bar mixing parameter Delta m_d using neutral B meson pairs in a 29.1 fb^{-1} data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We exclusively reconstruct one neutral B meson in the semileptonic B^0 \to D^{*-}\ell^+νdecay mode and identify the flavor of the accompanying B meson from its decay products. From the distribution of the time intervals between the two flavor-tagged B meson decay points, we obtain Delta m_d = (0.494 +- 0.012 +- 0.015) ps^{-1}, where the first error is statistical and the second error is systematic.
We report branching fractions and charge asymmetries for exclusive decays of charged and neutral B mesons to two-body final states containing a charmonium meson, J/psi or psi(2S). This result is based on a 29.4 fb^{-1} data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e+e- collider.