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The Belle Collaboration

Publications and source records attributed to The Belle Collaboration.

At least 127 records · Page 7Linked to original sources

arXiv2005

Improved Measurement of the Electroweak Penguin Process B->Xsll

We present an improved measurement of the branching fraction for the electroweak penguin process B->Xsll, 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 events collected with the Belle detector at the KEKB energy asymmetric e+e- collider. The Xs hadronic system is reconstructed from one K^{+-} or K^{0}_{S} and up to four pions, where at most one pion can be neutral. Averaging over both lepton flavors, the inclusive branching fraction is measured to be Br(B->Xsll)=(4.11+-0.83(stat)+0.85-0.81(syst))*10^{-6} for M_ll > 0.2GeV/c2.

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arXiv2004

Observation of the D1(2420)->DPI+PI- decays

We report on the first observation of $D_1\to Dπ^+π^-$ decays (where the contribution from the dominant known $D_1 \to D^* π$ decay mode is excluded) in the $B\to D_1π$ decays. The observation is based on $15.2\times 10^7 B\bar{B}$ events collected with the Belle detector at the KEKB collider. We also set 90% confidence level upper limits for the $D_2^*\to D^{(*)}π^+π^-$ and $D_1 \to D^*π^+π^-$ decays in the $B\to D^*_2π$ and $B\to D_1π$ decays, respectively.

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arXiv2004

Evidence for $B^+\toωl^+ ν$

We have searched for the decay $B^+\toωl^+ν$ ($l=e$ or $μ$) in 78 fb$^{-1}$ of $Υ(4S)$ data (85 million $B\bar B$ events) accumulated with the Belle detector. The final state is fully reconstructed using the $ω$ decay into $π^+π^-π^0$, combined with detector hermeticity to estimate the neutrino momentum. A signal of $414\pm 125$ events is found in the data, corresponding to a branching fraction of $(1.3\pm 0.4\pm 0.2\pm 0.3)\times 10^{-4}$, where the first two errors are statistical and systematic, respectively. The third error reflects the estimated form-factor uncertainty.

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arXiv2004

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.

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arXiv2004

Improved Measurements of Branching Fractions for B->Kpi, pipi and KK Decays

We report improved measurements of branching fractions for $B\to Kπ$, $π^+π^-$, $π^+π^0$ and $K\bar{K}$ decays based on a data sample of 85.0 million $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ storage ring. This data sample is almost three times larger than the sample previously used. We observe clear signals for $B\to Kπ$, $π^+π^-$ and $π^+π^0$ decays and set upper limits on $B\to K\bar{K}$ decays. The results can be used to give model-dependent constraints on the CKM angle $ϕ_3$, as well as limits on the hadronic uncertainty in the time-dependent analysis of the angle $ϕ_2$.

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arXiv2004

Observation of Radiative Decay $D^0 \to ϕγ$

We report the observation of the decay $D^{0} \to ϕγ$ with a statistical significance of $5.4σ$ in $78.1 \ifb$ of data collected by the Belle experiment at the KEKB $e^+ e^-$ collider. This is the first observation of a flavor-changing radiative decay of a charmed meson. The Cabibbo- and color-suppressed decays $D^0 \to ϕπ^0$, $ϕη$ are also observed for the first time. We measure branching fractions $\br(D^{0} \to ϕγ) = [ 2.60^{+0.70}_{-0.61} \stat {}^{+0.15}_{-0.17} \syst ] \times 10^{-5}$, $\br(D^{0} \to ϕπ^{0}) = [ 8.01 \pm 0.26 \stat \pm 0.47 \syst ] \times 10^{-4}$, and $\br(D^{0} \to ϕη) = [ 1.48 \pm 0.47 \stat \pm 0.09 \syst ] \times 10^{-4}$.

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arXiv2004

Observation of B+ -> psi(3770) K+

We report the first observation of the decay B+ -> psi(3770) K+ where psi(3770) is reconstructed in the D0D0-bar and D+D- decay channels. The obtained branching fraction is Br(B+ -> psi(3770) K+)=(0.48+-0.11+-0.07)x10^{-3}. We have measured the branching fraction for the decay B+ -> D0D0-bar K+ to be (1.17+-0.21+-0.15)x10^{-3}. We have set a 90% confidence level upper limit of 0.90x10^{-3} for the decay B+ -> D+D-K+. We also present the results of a search for possible decays to DD-bar and D0D0-bar pi0 of the recently observed X(3872) particle. The analysis is based on 88 fb^{-1} of data collected at the Upsilon(4S) resonance by the Belle detector at the KEKB asymmetric-energy e+e- collider.

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arXiv2003

Measurement of K^+K^- production in two-photon collisions in the resonant-mass region

K^+K^- production in two-photon collisions has been studied using a large data sample of 67 fb^{-1} accumulated with the Belle detector at the KEKB asymmetric e^+e^- collider. We have measured the cross section for the process gamma gamma -> K^+ K^- for center-of-mass energies between 1.4 and 2.4 GeV, and found three new resonant structures in the energy region between 1.6 and 2.4 GeV. The angular differential cross sections have also been measured.

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arXiv2003

Measurement of Time-Dependent CP-Violating Asymmetries in B0 --> phi Ks0, K+ K- Ks0, and eta' Ks0 Decays

We present an improved measurement of CP-violation parameters in B0 --> phi Ks0, K+ K- Ks0, and eta' Ks0 decays based on a 140 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. One neutral B meson is fully reconstructed in one of the specified decay channels, and the flavor of the accompanying B meson is identified from its decay products. CP-violation parameters for each of the three modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. We find that the observed CP asymmetry in the B0 --> phi Ks0 decay differs from the standard model (SM) expectation by 3.5 standard deviations, while the other cases are consistent with the SM.

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arXiv2003

Evidence for B0->pi0pi0

We report evidence for the decay B0->pi0pi0. The analysis is based on a data sample of 152million BBbar pairs collected at the Upsilon(4s) resonance with the Belle detector at the KEKB e+e- storage ring. We find 25.6+9.3/-8.4(stat)+1.6/-1.4(syst) B0->pi0pi0 signal events with a significance of 3.4 standard deviations. We measure the branching fraction to be (1.7+-0.6(stat)+-0.2(syst))*10^{-6}.

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arXiv2003

Measurement of CP-Violation Parameter sin(2phi1) with 152 Million BB-bar Pairs

We present a precise measurement of the standard model CP-violation parameter sin(2phi1) based on a sample of 152 x 10^6 BB-bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is reconstructed in a J/psi Ks0, psi(2S) Ks0, chi_c1 Ks0, eta_c Ks0, J/psi K*0, or J/psi KL CP-eigenstate decay channel and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time interval between the two B meson decay points, we obtain sin(2phi1) = 0.733 +/- 0.057(stat) +/- 0.028(syst).

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arXiv2003

Observation of a New Narrow Charmonium State in Exclusive B+-->K+ pi+pi- J/psi Decays

We report the first observation of a narrow charmmonium state produced in the exclusive decay process B+->K+ pi+pi- J/psi. This state, which decays into pi+pi-J/psi, has a mass of 3871.8+-0.7(stat)+-0.4(syst) MeV, which is very near the M_D + M_D* mass threshold. The results are based on an analysis of 152M BBbar events collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider.

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arXiv2003

Observation of the DsJ(2317) and DsJ(2460) in B decays

We report on a study of the B --> D DsJ(2317) and B --> D DsJ(2460) decays based on 123.7 x 10^6 BBar events collected with the Belle detector at KEKB. The B --> D DsJ(2317) and B --> D DsJ(2460) decays have been observed for the first time. We observe the DsJ(2317) decay to Ds pi0 and DsJ(2460) decay to the Ds* pi0 and Ds gamma final states. We also set the 90% CL upper limits for the decays DsJ(2317) --> Ds* gamma, DsJ(2460) --> Ds* gamma, DsJ(2460) --> Ds pi0 and DsJ(2460) --> Ds pi+ pi-.

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arXiv2002

Study of $\bar{B^{0}} \to D^{(*)0} π^+ π^-$ Decays

We report on a study of $\bar{B^{0}} \to D^{(*) 0} π^+ π^-$ decays using 29.1 fb$^{-1}$ of $e^{+}e^{-}$ annihilation data recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB storage ring. Making no assumptions about the intermediate mechanism, the branching fractions for $\bar{B}^0 \to D^0 π^+ π^-$ and $\bar{B}^0 \to D^{* 0} π^+ π^-$ are determined to be $(8.0 \pm 0.6 \pm 1.5) \times 10^{-4} $ and $ (6.2 \pm 1.2 \pm 1.8) \times 10^{-4}$ respectively. An analysis of $\bar{B^{0}} \to D^{0} π^+ π^-$ candidates yields to the first observation of the color-suppressed hadronic decay $\bar{B}^0 \to D^0 ρ^0$ with the branching fraction $(2.9 \pm 1.0 \pm 0.4) \times 10^{-4}$. We measure the ratio of branching fractions ${\mathcal B}(\bar{B^0} \to D^0 ρ^0) / {\mathcal B}(\bar{B^0} \to D^0 ω)$ = 1.6 $\pm$ 0.8.

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arXiv2002

Improved Measurement of Mixing-induced CP Violation in the Neutral B Meson System

We present an improved measurement of the standard model CP violation parameter sin2phi_1 (also known as sin2beta) based on a sample of 85 times 10^6 B Bbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is reconstructed in a J/psi K_S, psi(2S) K_S, chi_{c1} K_S, eta_c K_S, J/psi K^{*0}, or J/psi K_L CP-eigenstate decay channel and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time interval between the two B meson decay points, we obtain sin2phi_1 = 0.719 +/- 0.074(stat) +/- 0.035(syst).

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arXiv2002

Observation of Ds+ K- and evidence for Ds+ pi- final states in neutral B decays

We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel B0bar -> Ds+ K- is found in a sample of 85 timse 10^6 B Bbar events, collected with the Belle detector at KEKB, with a branching fraction Br(B0bar -> Ds+ K-)=(4.6^{+1.2}_{-1.1} +- 1.3) times 10^{-5}. We also obtain evidence for the B0 -> Ds+ pi- decay with branching fraction Br(B0 -> Ds+ pi-)=(2.4^{+1.0}_{-0.8} +- 0.7) times 10^{-5}. This value may be used to extract a model-dependent value of |Vub|.

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arXiv2002

Study of charmless B decays to three-kaon final states

We report on a study of charmless B meson decays to three-kaon final states. The results are obtained with a 78.7 1/fb data sample collected on the Y(4S) resonance by the Belle detector operating at the KEKB asymmetric energy $e^+e^-$ collider. The branching fractions for B decays to three-body K+K+K-, K0K+K-, KsKsK+, and KsKsKs final states are presented. We also make a first attempt to perform an isospin analysis of the three-kaon final states.

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arXiv2002

An Improved Measurement of Mixing-induced CP Violation in the Neutral B Meson System

We present an improved measurement of the standard model CP violation parameter sin2phi_1 (also known as sin2beta) based on a sample of 85 times 10^6 B Bbar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is reconstructed in a J/psi K_S, psi(2S) K_S, chi_{c1} K_S, eta_c K_S, J/psi K^{*0}, or J/psi K_L CP-eigenstate decay channel and the flavor of accompanying B meson is identified from itsdecay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we obtain sin2phi_1 = 0.719 +/- 0.074(stat) +/- 0.035(syst). We also report measurements of CP violation parameters for the related B^0 -> J/psi pi^0 decay mode and the penguin-dominated processes B^0 -> eta' K_S, phi K_S and K^+K^- K_S.

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