We report results from the first search for the rare penguin-dominated decay mode B0→KS0KS0γ, which can result from the production of tensor mesons f(1270) and f′(1525) in association with a photon. The search uses...
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We report results from the first search for the rare penguin-dominated decay mode B0→KS0KS0γ, which can result from the production of tensor mesons f(1270) and f′(1525) in association with a photon. The search uses the full data sample of 772×106 BB¯ pairs collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. No statistically significant signals are observed in the KS0KS0 invariant mass range 1 GeV/c2
We report the first direct measurement of the inclusive branching fraction B(Bs→DsX) via Bs tagging in e+e−→ϒ(5S) events. Tagging is accomplished through a partial reconstruction of semileptonic decays Bs→DsXℓν, w...
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We report the first direct measurement of the inclusive branching fraction B(Bs→DsX) via Bs tagging in e+e−→ϒ(5S) events. Tagging is accomplished through a partial reconstruction of semileptonic decays Bs→DsXℓν, where X denotes unreconstructed additional hadrons or photons and ℓ is an electron or muon. With 121.4 fb−1 of data collected at the ϒ(5S) resonance by the Belle detector at the KEKB asymmetric-energy e+e− collider, we obtain B(Bs→DsX)=(60.2±5.8±2.3)%, where the first uncertainty is statistical and the second is systematic.
We report measurements of the branching fractions and CP asymmetries for Ds+→K+η, Ds+→K+π0, and Ds+→π+η decays, and the branching fraction for Ds+→π+π0. Our results are based on a data sample corresponding t...
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We report measurements of the branching fractions and CP asymmetries for Ds+→K+η, Ds+→K+π0, and Ds+→π+η decays, and the branching fraction for Ds+→π+π0. Our results are based on a data sample corresponding to an integrated luminosity of 921 fb−1 collected by the Belle detector at the KEKB e+e− asymmetric-energy collider. Our measurements of CP asymmetries in these decays are the most precise to date; no evidence for CP violation is found.
Using the entire data sample of 980 fb−1 collected with the Belle detector at the KEKB asymmetric-energy e+e− collider, we present measurements of the branching fractions of the Cabibbo-favored decays Ξc0→ΛKS0, ...
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Using the entire data sample of 980 fb−1 collected with the Belle detector at the KEKB asymmetric-energy e+e− collider, we present measurements of the branching fractions of the Cabibbo-favored decays Ξc0→ΛKS0, Ξc0→Σ0KS0, and Ξc0→Σ+K−. Taking the decay Ξc0→Ξ−π+ as the normalization mode, we measure the branching fraction ratio B(Ξc0→ΛKS0)/B(Ξc0→Ξ−π+)=0.229±0.008±0.012 with improved precision, and measure the branching fraction ratios B(Ξc0→Σ0KS0)/B(Ξc0→Ξ−π+)=0.038±0.006±0.004 and B(Ξc0→Σ+K−)/B(Ξc0→Ξ−π+)=0.123±0.007±0.010 for the first time. Taking into account the branching fraction of the normalization mode, the absolute branching fractions are determined to be B(Ξc0→ΛKS0)=(3.27±0.11±0.17±0.73)×10−3, B(Ξc0→Σ0KS0)=(0.54±0.09±0.06±0.12)×10−3, and B(Ξc0→Σ+K−)=(1.76±0.10±0.14±0.39)×10−3. The first and second uncertainties above are statistical and systematic, respectively, while the third ones arise from the uncertainty of the branching fraction of Ξc0→Ξ−π+.
For the first time we search for the ηc2(1D) in e+e−→γηc2(1D) at s=10.52, 10.58, and 10.867 GeV with data samples of 89.5 fb−1, 711 fb−1, and 121.4 fb−1, respectively, accumulated with the Belle detector at the...
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For the first time we search for the ηc2(1D) in e+e−→γηc2(1D) at s=10.52, 10.58, and 10.867 GeV with data samples of 89.5 fb−1, 711 fb−1, and 121.4 fb−1, respectively, accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant ηc2(1D) signal is observed in the mass range between 3.8 and 3.88 GeV/c2. The upper limit at 90% confidence level on the product of the Born cross section for e+e−→γηc2(1D) and branching fraction for ηc2(1D)→γhc(1P) is determined to be σ(e+e−→γηc2(1D))B(ηc2(1D)→γhc(1P))<4.9 fb at s near 10.6 GeV.
We report the results of a first search for a doubly charged DDK bound state, denoted the R++, in ϒ(1S) and ϒ(2S) inclusive decays and via direct production in e+e− collisions at s=10.520, 10.580, and 10.867 GeV. The ...
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We report the results of a first search for a doubly charged DDK bound state, denoted the R++, in ϒ(1S) and ϒ(2S) inclusive decays and via direct production in e+e− collisions at s=10.520, 10.580, and 10.867 GeV. The search uses data accumulated with the Belle detector at the KEKB asymmetric-energy e+e− collider. No significant signals are observed in the D+Ds*+ invariant-mass spectra of all studied modes. The 90% credibility level upper limits on their product branching fractions in ϒ(1S) and ϒ(2S) inclusive decays (B(ϒ(1S, 2S)→R+++anything)×B(R++→D+Ds*+)), the product values of Born cross section and branching fraction in e+e− collisions (σ(e+e−→R+++anything)×B(R++→D+Ds*+)) at s=10.520, 10.580, and 10.867 GeV under different assumptions of R++ masses varying from 4.13 to 4.17 GeV/c2 and widths varying from 0 to 5 MeV are obtained.
Using 980.6 fb−1 of data collected with the Belle detector operating at the KEKB asymmetric-energy e+e− collider, we present a measurement of the branching fraction of the singly Cabibbo-suppressed decay Λc+→pω. A...
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Using 980.6 fb−1 of data collected with the Belle detector operating at the KEKB asymmetric-energy e+e− collider, we present a measurement of the branching fraction of the singly Cabibbo-suppressed decay Λc+→pω. A clear Λc+ signal is observed for Λc+→pω with a statistical significance of 9.1 standard deviations, and we measure the ratio of branching fractions B(Λc+→pω)/B(Λc+→pK−π+)=(1.32±0.12(stat)±0.10(syst))×10−2, from which we infer the branching fraction B(Λc+→pω)=(8.27±0.75(stat)±0.62(syst)±0.42(ref))×10−4. The first quoted uncertainty is statistical, the second systematic, and the third from the reference mode Λc+→pK−π+.
We search for lepton-number- and baryon-number-violating decays τ−→p¯e+e−, pe−e−, p¯e+μ−, p¯e−μ+, p¯μ+μ−, and pμ−μ− using 921 fb−1 of data, equivalent to (841±12)×106 τ+τ− even...
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We search for lepton-number- and baryon-number-violating decays τ−→p¯e+e−, pe−e−, p¯e+μ−, p¯e−μ+, p¯μ+μ−, and pμ−μ− using 921 fb−1 of data, equivalent to (841±12)×106 τ+τ− events, recorded with the Belle detector at the KEKB asymmetric-energy e+e− collider. In the absence of a signal, 90% confidence-level upper limits are set on the branching fractions of these decays in the range (1.8−4.0)×10−8. We set the world’s first limits on the first four channels and improve the existing limits by an order of magnitude for the last two channels.
We present measurements of partial branching fractions of inclusive semileptonic B→Xuℓ+νℓ decays using the full Belle dataset of 711 fb−1 of integrated luminosity at the ϒ(4S) resonance and for ℓ=e, μ. Inclusive s...
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We present measurements of partial branching fractions of inclusive semileptonic B→Xuℓ+νℓ decays using the full Belle dataset of 711 fb−1 of integrated luminosity at the ϒ(4S) resonance and for ℓ=e, μ. Inclusive semileptonic B→Xuℓ+νℓ decays are Cabibbo-Kobayashi-Maskawa (CKM) suppressed and measurements are complicated by the large background from CKM favored B→Xcℓ+νℓ transitions, which have a similar signature. Using machine learning techniques, we reduce this and other backgrounds effectively, while retaining access to a large fraction of the B→Xuℓ+νℓ phase space and high signal efficiency. We measure partial branching fractions in three phase-space regions covering about 31% to 86% of the accessible B→Xuℓ+νℓ phase space. The most inclusive measurement corresponds to the phase space with lepton energies of EℓB>1 GeV, and we obtain ΔB(B→Xuℓ+νℓ)=(1.59±0.07±0.16)×10−3 from a two-dimensional fit of the hadronic mass spectrum and the four-momentum-transfer squared distribution, with the uncertainties denoting the statistical and systematic error. We find |Vub|=(4.10±0.09±0.22±0.15)×10−3 from an average of four calculations for the partial decay rate with the third uncertainty denoting the average theory error. This value is higher but compatible with the determination from exclusive semileptonic decays within 1.3 standard deviations. In addition, we report charmless inclusive partial branching fractions separately for B+ and B0 mesons as well as for electron and muon final states. No isospin breaking or lepton flavor universality violating effects are observed.
We report branching fraction measurements of four decay modes of the Λc+ baryon, each of which includes an η meson and a Λ baryon in the final state, and all of which are measured relative to the Λc+→pK−π+ decay...
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We report branching fraction measurements of four decay modes of the Λc+ baryon, each of which includes an η meson and a Λ baryon in the final state, and all of which are measured relative to the Λc+→pK−π+ decay mode. The results are based on a 980 fb−1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e− collider. Two decays, Λc+→ηΣ0π+ and Λ(1670)π+, are observed for the first time, while the measurements of the other decay modes, Λc+→ηΛπ+ and ηΣ(1385)+, are more precise than those made previously. We obtain relative branching fractions of B(Λc+→ηΛπ+)/B(Λc+→pK−π+)=0.293±0.003±0.014, B(Λc+→ηΣ0π+)/B(Λc+→pK−π+)=0.120±0.006±0.010, B(Λc+→Λ(1670)π+)×B(Λ(1670)→ηΛ)/B(Λc+→pK−π+)=(5.54±0.29±0.73)×10−2, and B(Λc+→ηΣ(1385)+)/B(Λc+→pK−π+)=0.192±0.006±0.016. The mass and width of the Λ(1670) are also precisely determined to be 1674.3±0.8±4.9 MeV/c2 and 36.1±2.4±4.8 MeV, respectively, where the uncertainties are statistical and systematic, respectively.
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