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The Belle Collaboration

Publications and source records attributed to The Belle Collaboration.

138 records · Page 8Linked to original sources
arXiv2002

Study of CP-Violating Asymmetries in B0 -> pi+pi- Decays

We present a measurement of CP-violating asymmetries in B0 -> pi+pi- decays based on a 41.8 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We fully reconstruct one neutral B meson as a B0 -> pi+pi- CP eigenstate and identify the flavor of the accompanying B meson from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we obtain the CP-violating asymmetry parameters Spipi = -1.21 +0.38/-0.27(stat) +0.16/-0.13(syst) and Apipi = +0.94 +0.25/-0.31(stat) +/- 0.09(syst).

hep-ex↗
arXiv2002

Observation of Double cc bar Production in e+ e- Annihilation at sqrt{s} ~ 10.6 GeV

We report the observation of prompt J/psi via double ccbar production from the e+e- continuum. In this process one ccbar pair fragments into a J/psi meson while the remaining pair either produces a bound charmonium state or fragments into open charm. Both cases have been observed: the first by studying the mass spectrum of the system recoiling against the J/psi, and the second by reconstructing the J/psi together with a charmed meson. We find cross-sections of σ(e+ e- -> J/psi eta_c (gamma)) * BR (eta_c -> >=4 charged) = 0.033 (+0.007 -0.006)(stat) \pm 0.009(syst)pb and σ(e+ e- -> J/psi D*+ X) = 0.53 (+0.19 -0.15)(stat) \pm 0.14(syst) pb, and infer σ(e+ e- -> J/psi c cbar) / σ(e+ e- -> J/psi X) = 0.59 (+0.15 -0.13)(stat) \pm 0.12(syst). These results are obtained from a 46.2/fb data sample collected near the Upsilon(4S) resonance, with the Belle detector at the KEKB asymmetric energy e+ e- collider.

hep-ex↗
arXiv2002

Observation of B0bar --> D(*)0 p pbar

The B meson decay modes B --> D p pbar and B --> D* p pbar have been studied using 29.4 fb^{-1} of data collected with the Belle detector at KEKB. The B0bar --> D0 p pbar and B0bar --> D*0 p pbar decays have been observed for the first time with branching fractions Br(B0bar --> D0 p pbar) =(1.18\pm 0.15\pm 0.16) 10^{-4} and Br(B0bar --> D*0 p pbar) =(1.20^{+0.33}_{-0.29}\pm 0.21) 10^{-4}. No signal has been found for the B+ --> D+ p pbar and B+ --> D*+ p pbar decay modes, and the corresponding upper limits at 90% C.L. are presented.

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arXiv2002

Search for Charmless Two-body Baryonic Decays of B Mesons

We report the results of a search for the rare baryonic decays $B^0 \to p\bar{p}$, $Λ\barΛ$, and $B^+ \to p\barΛ$. The analysis is based on a data set of $31.7\times 10^6 B\bar{B}$ events collected by the Belle detector at the KEKB $e^+e^-$ collider. No statistically significant signals are found, and we set branching fraction upper limits ${\mathcal B}(B^0 \to p\bar{p}) < 1.2 \times 10^{-6}$, ${\mathcal B}(B^0 \to Λ\barΛ) < 1.0 \times 10^{-6}$, and ${\mathcal B}(B^+ \to p\barΛ) < 2.2 \times 10^{-6}$ at the 90% confidence level.

hep-ex↗
arXiv2002

Observation of $B^{\pm}\to p \bar{p} K^{\pm}$

We report the observation of the decay mode $B^{\pm}\to p \bar{p} K^{\pm}$ based on an analysis of 29.4 fb$^{-1}$ of data collected by the Belle detector at KEKB. This is the first example of a $b\to s$ transition with baryons in the final state. The $p \bar{p}$ mass spectrum in this decay is inconsistent with phase space and is peaked at low mass. The branching fraction for this decay is measured to be ${\cal B}(B^{\pm}\to p \bar{p} K^{\pm}) =(4.3^{+1.1}_{-0.9}({\rm stat})\pm 0.5({\rm syst}))\times 10^{-6}.$ We also report upper limits for the decays $B^0\to p \bar{p} K_S$ and $B^{\pm}\to p \bar{p} π^{\pm}$.

hep-ex↗
arXiv2001

Observation of Color-suppressed $\bar{B}^0 \to D^{0}π^0$, $D^{*0}π^0$, $D^0η$, and $D^0ω$ Decays

We report the first observation of color-suppressed $\bar{B}{}^0 \to D^0 π^0$, $D^{*0} π^0$, $D^{0} η$, and $D^{0}ω$ decays and evidence for $\bar{B}{}^0 \to D^{*0} η$ and $D^{*0}ω$. The branching fractions are found to be ${\cal B} (\bar{B}{}^0 \to D^0 π^0) = (3.1 \pm 0.4 \pm 0.5) \times 10^{-4}$, ${\cal B} (\bar{B}{}^0 \to D^{*0} π^0) = (2.7 ^{+0.8}_{-0.7} ^{+0.5}_{-0.6})\times 10^{-4}$, ${\cal B} (\bar{B}{}^0 \to D^0 η) = (1.4 ^{+0.5}_{-0.4}\pm 0.3) \times 10^{-4}$, ${\cal B} (\bar{B}{}^0 \to D^0 ω) = (1.8 \pm 0.5 ^{+0.4}_{-0.3}) \times 10^{-4}$, and we set 90% confidence level upper limits of ${\cal B} (\bar{B}{}^0 \to D^{*0} η) < 4.6\times 10^{-4}$ and ${\cal B} (\bar{B}{}^0 \to D^{*0} ω) < 7.9 \times 10^{-4}$. The analysis is based on a data sample of 21.3 fb$^{-1}$ collected at the $Υ(4S)$ resonance by the Belle detector at the KEKB $e^{+} e^{-}$ collider.

hep-ex↗
arXiv2001

Belle B Physics Results

B physics results from the Belle experiment are reviewed. Precise measurements of Cabbibo-Kobayashi-Maskawa matrix elements are made. Several decay modes are observed which will enable us to measure the CP angles, phi_i in channels other than B0->psi K0 modes. New rare decay modes are observed in many channels. Particular attention is paid to the first observation of the electroweak penguin-mediated decay.

hep-ex↗
arXiv2001

Observation of Large CP Violation in the Neutral B Meson System

We present a measurement of the Standard Model CP violation parameter sin 2phi_1 based on 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. One neutral B meson is fully reconstructed as a J/psi Ks, psi(2S) Ks, chi_c1 Ks, eta_c Ks, J/psi K_L or J/psi K^{*0} decay and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we determine sin 2phi_1 = 0.99 +- 0.14(stat) +- 0.06(syst). We conclude that we have observed CP violation in the neutral B meson system.

hep-ex↗
arXiv2001

Observation of Color-Suppressed $\overline{B}^0 \to D^{(*)0}X^0$ Decays

We report the first observation of color-suppressed $\overline{B}^0\to D^0 π^0$ and $D^{(*)0} ω$ decays and evidence of $\overline{B}^0 \to D^{*0} π^0$ and $D^{(*)0} η$. The branching fractions are found to be ${\cal B} (\overline{B}^0\to D^0 π^0) = (2.9 ^{+0.4}_{-0.3} \pm 0.6) \times 10^{-4}$, ${\cal B} (\overline{B}^0 \to D^0 ω) = (1.7 ^{+0.5 +0.3}_{-0.4 -0.4}) \times 10^{-4}$, and ${\cal B} (\overline{B}^0 \to D^{*0} ω) = (3.4 ^{+1.3}_{-1.1}\pm 0.8) \times 10^{-4}$. The analysis is based on a data sample of 21.3 fb$^{-1}$ collected at the $Υ(4S)$ resonance by the Belle detector at the KEKB $e^{+} e^{-}$ collider.

hep-ex↗
arXiv2001

Observation of $B^+ \to χ_{c0} K^+ $

We report the first observation of the decay $B^+ \to χ_{c0} K^+$ using 21.3 fb$^{-1}$ of data collected by the Belle detector at the $Υ$(4S) resonance. The preliminary result for the branching fraction is ${\cal{B}}(B^+\to χ_{c0}K^+)=(8.0^{+2.7}_{-2.4}\pm 1.0\pm 1.1)\times 10^{-4}$ where the first error is statistical, the second is systematic, and the third comes from the uncertainty in the $χ_{c0}\toπ^+π^-$ branching fraction.

hep-ex↗
arXiv2001

Study of three-body charmless B decays at Belle

Using a data sample of 21.3 fb$^{-1}$ collected by the Belle detector, three body charmless decays $B^+\to K^+ h^+ h^-$ have been studied. With no assumptions on the intermediate mechanisms, the following branching fractions have been measured for the first time $ {\cal{B}}(B^+\to K^+ π^- π^+) = (58.5\pm 7.1\pm 8.8)\times 10^{-6}$ and $ {\cal{B}}(B^+\to K^+ K^- K^+) = (37.0\pm 3.9\pm 4.4)\times 10^{-6}$. We also present the first observations of the decay mode $B^+\to K^{*0}(892)π^+$ with a branching fraction of ${\cal{B}}(B^+\to K^{*0}(892) π^+) = (16.7^{+3.7+2.1+3.0}_{-3.4-2.1-5.9})\times 10^{-6}$ and the decay mode $B^+\to f_0(980)K^+$ with a product branching fraction of ${\cal{B}}(B^+\to f_0(980) K^+)\times{\cal{B}}(f_0(980)\to π^+π^-) = (11.7^{+2.5+1.5+4.1}_{-2.7-1.5-1.0})\times 10^{-6}$.

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