Using a data sample of 772×106 BB¯ pairs collected on the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e− collider, we report the observation of B0→pp¯π+π− and the first o...
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Using a data sample of 772×106 BB¯ pairs collected on the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e− collider, we report the observation of B0→pp¯π+π− and the first observation of B+→pp¯π+π0. We measure a decay branching fraction of (0.83±0.17±0.17)×10−6 in B0→pp¯π+π− for Mπ+π−<1.22 GeV/c2 with a significance of 5.5 standard deviations. The contribution from B0→pp¯K0 is excluded. We measure a decay branching fraction of (4.58±1.17±0.67)×10−6 for B+→pp¯π+π0 with Mπ+π0<1.3 GeV/c2 with a significance of 5.4 standard deviations. We study the difference of the Mpp¯ distributions in B0→pp¯π+π− and B+→pp¯π+π0.
We report results from a search for the decay Bs0→ηη using 121.4 fb−1 of data collected at the ϒ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We do not observe any signal and ...
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We report results from a search for the decay Bs0→ηη using 121.4 fb−1 of data collected at the ϒ(5S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We do not observe any signal and set an upper limit on the branching fraction of 14.3×10−5 at 90% confidence level. This result represents a significant improvement over the previous most stringent limit.
We report the first observation of the double strange baryon Ξ(1620)0 in its decay to Ξ−π+ via Ξc+→Ξ−π+π+ decays based on a 980 fb−1 data sample collected with the Belle detector at the KEKB asymmetric-energy...
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We report the first observation of the double strange baryon Ξ(1620)0 in its decay to Ξ−π+ via Ξc+→Ξ−π+π+ decays based on a 980 fb−1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. The mass and width are measured to be 1610.4±6.0(stat)−4.2+6.1 (syst) MeV/c2 and 59.9±4.8(stat)−7.1+2.8(syst) MeV, respectively. We obtain 4.0σ evidence of the Ξ(1690)0 with the same data sample. These results shed light on the structure of hyperon resonances with strangeness S=−2.
We report the first observation of the radiative decay of the ϒ(1S) into a charmonium state. The significance of the observed signal of ϒ(1S)→γχc1 is 6.3 standard deviations including systematics. The branching fra...
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We report the first observation of the radiative decay of the ϒ(1S) into a charmonium state. The significance of the observed signal of ϒ(1S)→γχc1 is 6.3 standard deviations including systematics. The branching fraction is calculated to be B[ϒ(1S)→γχc1]=[4.7−1.8+2.4(stat)−0.5+0.4(sys)×10−5]. We also searched for ϒ(1S) radiative decays into χc0,2 and ηc(1S,2S), and set upper limits on their branching fractions. These results are obtained from a 24.9 fb−1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e− collider at a center-of-mass energy equal to the ϒ(2S) mass using ϒ(1S) tagging by the ϒ(2S)→ϒ(1S)π+π− transitions.
We present the results of the first Dalitz plot analysis of the decay D0→K−π+η. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb−1 collected by the Belle detector at the ...
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We present the results of the first Dalitz plot analysis of the decay D0→K−π+η. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb−1 collected by the Belle detector at the asymmetric-energy e+e− KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K¯*(892)0η, K−a0(980)+, K−a2(1320)+, K¯*(1410)0η, K*(1680)−π+ and K2*(1980)−π+, together with Kπ and Kη S-wave components. The decays K*(1680)−→K−η and K2*(1980)−→K−η are observed for the first time. We measure ratio of the branching fractions, B(D0→K−π+η)B(D0→K−π+)=0.500±0.002(stat)±0.020(syst)±0.003(BPDG). Using the Dalitz fit result, the ratio B(K*(1680)→Kη)B(K*(1680)→Kπ) is measured to be 0.11±0.02(stat)−0.04+0.06(syst)±0.04(BPDG); this is much lower than the theoretical expectations (≈1) made under the assumption that K*(1680) is a pure 13D1 state. The product branching fraction B(D0→[K2*(1980)−→K−η]π+)=(2.2−1.9+1.7)×10−4 is determined. In addition, the πη′ contribution to the a0(980)± resonance shape is confirmed with 10.1σ statistical significance using the three-channel Flatté model. We also measure B(D0→K¯*(892)0η)=(1.41−0.12+0.13)%. This is consistent with, and more precise than, the current world average (1.02±0.30)%, deviates with a significance of more than 3σ from the theoretical predictions of (0.51–0.92)%.
The experimental results on the ratios of branching fractions R(D)=B(B¯→Dτ−ν¯τ)/B(B¯→Dℓ−ν¯ℓ) and R(D*)=B(B¯→D*τ−ν¯τ)/B(B¯→D*ℓ−ν¯ℓ), where ℓ denotes an electron or a ...
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The experimental results on the ratios of branching fractions R(D)=B(B¯→Dτ−ν¯τ)/B(B¯→Dℓ−ν¯ℓ) and R(D*)=B(B¯→D*τ−ν¯τ)/B(B¯→D*ℓ−ν¯ℓ), where ℓ denotes an electron or a muon, show a long-standing discrepancy with the standard model predictions, and might hint at a violation of lepton flavor universality. We report a new simultaneous measurement of R(D) and R(D*), based on a data sample containing 772×106 BB¯ events recorded at the ϒ(4S) resonance with the Belle detector at the KEKB e+e− collider. In this analysis the tag-side B meson is reconstructed in a semileptonic decay mode and the signal-side τ is reconstructed in a purely leptonic decay. The measured values are R(D)=0.307±0.037±0.016 and R(D*)=0.283±0.018±0.014, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the standard model predictions within 0.2, 1.1, and 0.8 standard deviations for R(D), R(D*), and their combination, respectively. This work constitutes the most precise measurements of R(D) and R(D*) performed to date as well as the first result for R(D) based on a semileptonic tagging method.
We report the observation of ϒ(2S)→γηb(1S) decay based on an analysis of the inclusive photon spectrum of 24.7 fb−1 of e+e− collisions at the ϒ(2S) center-of-mass energy collected with the Belle detector at the KE...
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We report the observation of ϒ(2S)→γηb(1S) decay based on an analysis of the inclusive photon spectrum of 24.7 fb−1 of e+e− collisions at the ϒ(2S) center-of-mass energy collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. We measure a branching fraction of B[ϒ(2S)→γηb(1S)]=(6.1−0.7−0.6+0.6+0.9)×10−4 and derive an ηb(1S) mass of 9394.8−3.1−2.7+2.7+4.5 MeV/c2, where the uncertainties are statistical and systematic, respectively. The significance of our measurement is greater than 7 standard deviations, constituting the first observation of this decay mode.
The branching fractions of the decays B+→ηℓ+νℓ and B+→η′ℓ+νℓ are measured, where ℓ is either an electron or a muon, using a data sample of 711 fb−1 containing 772×106BB¯ pairs collected at the ϒ(4S) ...
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The branching fractions of the decays B+→ηℓ+νℓ and B+→η′ℓ+νℓ are measured, where ℓ is either an electron or a muon, using a data sample of 711 fb−1 containing 772×106BB¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. To reduce the dependence of the result on the form factor model, the measurement is performed over the entire q2 range. The resulting branching fractions are B(B+→ηℓ+νℓ)=(2.83±0.55(stat.)±0.34(syst.))×10−5 and B(B+→η′ℓ+νℓ)=(2.79±1.29(stat.)±0.30(syst.))×10−5.
We report a measurement of time-dependent CP violation in B0→KS0π0π0 decays using a data sample of 772×106 BB¯ pairs collected by the Belle experiment running at the ϒ(4S) resonance at the KEKB e+e− coll...
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We report a measurement of time-dependent CP violation in B0→KS0π0π0 decays using a data sample of 772×106 BB¯ pairs collected by the Belle experiment running at the ϒ(4S) resonance at the KEKB e+e− collider. This decay proceeds mainly via a b→sdd¯ “penguin” amplitude. The results are sin2ϕ1eff=0.92−0.31+0.27 (stat.) ±0.11 (syst.) and A=0.28±0.21 (stat.) ±0.04 (syst.), which are the most precise measurements of CP violation in this decay mode to date. The value for the CP-violating parameter sin2ϕ1eff is consistent with that obtained using decay modes proceeding via a b→cc¯s “tree” amplitude.
This work reports the first observation of azimuthal asymmetries around the thrust axis in e+e− annihilation of pairs of back-to-back charged pions in one hemisphere, and π0 and η mesons in the opposite hemisphere. ...
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This work reports the first observation of azimuthal asymmetries around the thrust axis in e+e− annihilation of pairs of back-to-back charged pions in one hemisphere, and π0 and η mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The π0 and η asymmetries rise with the relative momentum z of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function H1⊥ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the η final states will provide additional information on the flavor structure of H1⊥. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb−1 collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.
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