From April to July 2018,a data sample at the peak energy of the T(4 S) resonance was collected with the Belle Ⅱ detector at the SuperKEKB electron-positron *** is the first data sample of the Belle Ⅱ *** Bhabha and ...
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From April to July 2018,a data sample at the peak energy of the T(4 S) resonance was collected with the Belle Ⅱ detector at the SuperKEKB electron-positron *** is the first data sample of the Belle Ⅱ *** Bhabha and digamma events,we measure the integrated luminosity of the data sample to be(496.3±0.3±3.0) pb-1,where the first uncertainty is statistical and the second is *** work provides a basis for future luminosity measurements at Belle Ⅱ.
We present a search for the decays of B0 mesons into a final state containing a Λ baryon and missing energy. These results are obtained from a 711 fb−1 data sample that contains 772×106 BB¯ pairs and was ...
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We present a search for the decays of B0 mesons into a final state containing a Λ baryon and missing energy. These results are obtained from a 711 fb−1 data sample that contains 772×106 BB¯ pairs and was collected near the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We use events in which one B meson is fully reconstructed in a hadronic decay mode and require the remainder of the event to consist of only a single Λ. No evidence for these decays is found, and we set 90% confidence level upper limits on the branching fractions in the range 2.1–3.8×10−5. This measurement provides the world’s most restrictive limits, with implications for baryogenesis and dark matter production.
We report the measurement of branching fractions and CP-violation asymmetries in B→ϕϕK decays based on a 711 fb−1 data sample containing 772×106 BB¯ events. The data were recorded at the ϒ(4S) resonance w...
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We report the measurement of branching fractions and CP-violation asymmetries in B→ϕϕK decays based on a 711 fb−1 data sample containing 772×106 BB¯ events. The data were recorded at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. For B+→ϕϕK+, the branching fraction and CP-violation asymmetry measured below the ηc threshold (mϕϕ<2.85 GeV/c2) are [3.43−0.46+0.48(stat)±0.22(syst)]×10−6 and −0.02±0.11(stat)±0.01(syst), respectively. Similarly, the branching fraction obtained for B0→ϕϕK0 below the ηc threshold is [3.02−0.66+0.75(stat)±0.20(syst)]×10−6. We also measure the CP-violation asymmetry for B+→ϕϕK+ within the ηc region (mϕϕ∈[2.94,3.02] GeV/c2) to be +0.12±0.12(stat)±0.01(syst).
We present the first observation of the Ωc0→Ω−μ+νμ decay and present measurements of the branching fraction ratios of the Ωc0→Ω−ℓ+νℓ decays compared to the reference mode Ωc0→Ω−π+, (ℓ=e or μ). This anal...
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We present the first observation of the Ωc0→Ω−μ+νμ decay and present measurements of the branching fraction ratios of the Ωc0→Ω−ℓ+νℓ decays compared to the reference mode Ωc0→Ω−π+, (ℓ=e or μ). This analysis is based on 89.5 fb−1, 711 fb−1, and 121.1 fb−1 data samples collected with the Belle detector at the KEKB asymmetric-energy e+e− collider at the center-of-mass energies of 10.52 GeV, 10.58 GeV, and 10.86 GeV, respectively. The Ωc0 signal yields are extracted by fitting MΩℓ and MΩπ spectra. The branching fraction ratios B(Ωc0→Ω−e+νe)/B(Ωc0→Ω−π+) and B(Ωc0→Ω−μ+νμ)/B(Ωc0→Ω−π+) are measured to be 1.98±0.13(stat)±0.08(syst) and 1.94±0.18(stat)±0.10(syst), respectively. The ratio of B(Ωc0→Ω−e+νe)/B(Ωc0→Ω−μ+νμ) is measured to be 1.02±0.10(stat)±0.02(syst), which is consistent with the expectation of lepton flavor universality.
The first measurements of differential branching fractions of inclusive semileptonic B→Xuℓ+νℓ decays are performed using the full Belle data set of 711 fb−1 of integrated luminosity at the ϒ(4S) resonance and for ℓ...
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The first measurements of differential branching fractions of inclusive semileptonic B→Xuℓ+νℓ decays are performed using the full Belle data set of 711 fb−1 of integrated luminosity at the ϒ(4S) resonance and for ℓ=e, μ. With the availability of these measurements, new avenues for future shape-function model-independent determinations of the Cabibbo-Kobayashi-Maskawa matrix element |Vub| can be pursued to gain new insights in the existing tension with respect to exclusive determinations. The differential branching fractions are reported as a function of the lepton energy, the four-momentum-transfer squared, light-cone momenta, the hadronic mass, and the hadronic mass squared. They are obtained by subtracting the backgrounds from semileptonic B→Xcℓ+νℓ decays and other processes, and corrected for resolution and acceptance effects.
We search for a new gauge boson Z′ that couples only to heavy leptons and their corresponding neutrinos in the process e+e−→Z′(→μ+μ−)μ+μ−, using a 643 fb−1 data sample collected by the Belle experiment at or ...
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We search for a new gauge boson Z′ that couples only to heavy leptons and their corresponding neutrinos in the process e+e−→Z′(→μ+μ−)μ+μ−, using a 643 fb−1 data sample collected by the Belle experiment at or near the ϒ(1S,2S,3S,4S,5S) resonances at the KEKB collider. While previous searches for Z′ performed a data-based estimation of the initial state radiation effect, our search for the Z′ is the first to include effects due to initial state radiation in the signal simulated samples that were used in estimating the detection efficiency. No signal is observed in the Z′ mass range of 0.212–10 GeV/c2, and we set an upper limit on the coupling strength, g′, constraining the possible Z′ contribution to the anomalous magnetic dipole moment of the muon.
We measure the branching fractions and CP asymmetries for the decays B0→D¯0π0 and B+→D¯0π+, using a data sample of 772×106 BB¯ pairs collected at the ϒ(4S) resonance with the Belle detector at...
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We measure the branching fractions and CP asymmetries for the decays B0→D¯0π0 and B+→D¯0π+, using a data sample of 772×106 BB¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB e+e− collider. The branching fractions obtained and direct CP asymmetries are B(B0→D¯0π0)=[2.70±0.06(stat)±0.10(syst)]×10−4, B(B+→D¯0π+)=[4.53±0.02(stat)±0.15(syst)]×10−3, ACP(B0→D¯0π0)=[+0.42±2.05(stat)±1.22(syst)]%, and ACP(B+→D¯0π+)=[+0.19±0.36(stat)±0.57(syst)]%. The measurements of B are the most precise to date and are in good agreement with previous results, as is the measurement of ACP(B+→D¯0π+). The measurement of ACP for B0→D¯0π0 is the first for this mode, and the value is consistent with Standard Model expectations.
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.
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