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.
We present a measurement of RK*, the branching fraction ratio B(B→K*μ+μ−)/B(B→K*e+e−), for both charged and neutral B mesons. The ratio for the charged case RK*+ is the first measurement ever performed. In additio...
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We present a measurement of RK*, the branching fraction ratio B(B→K*μ+μ−)/B(B→K*e+e−), for both charged and neutral B mesons. The ratio for the charged case RK*+ is the first measurement ever performed. In addition, we report absolute branching fractions for the individual modes in bins of the squared dilepton invariant mass q2. The analysis is based on a data sample of 711 fb−1, containing 772×106 BB¯ events, recorded at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. The obtained results are consistent with standard model expectations.
Using a data sample of 980 fb−1 collected with the Belle detector operating at the KEKB asymmetric-energy e+e− collider, we present evidence for the Ω(2012)− in the resonant substructure of Ωc0→π+(K¯Ξ)− ((K...
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Using a data sample of 980 fb−1 collected with the Belle detector operating at the KEKB asymmetric-energy e+e− collider, we present evidence for the Ω(2012)− in the resonant substructure of Ωc0→π+(K¯Ξ)− ((K¯Ξ)−=K−Ξ0+K¯0Ξ−) decays. The significance of the Ω(2012)− signal is 4.2σ after considering the systematic uncertainties. The ratio of the branching fraction of Ωc0→π+Ω(2012)−→π+(K¯Ξ)− relative to that of Ωc0→π+Ω− is calculated to be 0.220±0.059(stat.)±0.035(syst.). The individual ratios of the branching fractions of the two isospin modes are also determined and found to be B(Ωc0→π+Ω(2012)−)×B(Ω(2012)−→K−Ξ0)/B(Ωc0→π+K−Ξ0)=(9.6±3.2(stat.) ±1.8(syst.))% and B(Ωc0→π+Ω(2012)−)×B(Ω(2012)−→K¯0Ξ−)/B(Ωc0→π+K¯0Ξ−)=(5.5±2.8(stat.) ±0.7(syst.))%.
We present the measurement of the first to fourth order moments of the four-momentum transfer squared, q2, of inclusive B→Xcℓ+νℓ decays using the full Belle dataset of 711 fb−1 of integrated luminosity at the ϒ(4S)...
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We present the measurement of the first to fourth order moments of the four-momentum transfer squared, q2, of inclusive B→Xcℓ+νℓ decays using the full Belle dataset of 711 fb−1 of integrated luminosity at the ϒ(4S) resonance where ℓ=e, μ. The determination of these moments and their systematic uncertainties open new pathways to determine the absolute value of the Cabibbo-Kobayashi-Maskawa matrix element Vcb using a reduced set of matrix elements of the heavy quark expansion. In order to identify and reconstruct the Xc system, we reconstruct one of the two B-mesons using machine learning techniques in fully hadronic decay modes. The moments are measured with progressively increasing threshold selections on q2 starting with a lower value of 3.0 GeV2 in steps of 0.5 GeV2 up to a value of 10.0 GeV2. The measured moments are further unfolded, correcting for reconstruction and selection effects as well as QED final state radiation. We report the moments separately for electron and muon final states and observe no lepton flavor universality violating effects.
We report measurements of the branching fractions of singly Cabibbo-suppressed decays Λc+→pη and Λc+→pπ0 using the full Belle data sample corresponding to an integrated luminosity of 980.6 fb−1. The data were c...
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We report measurements of the branching fractions of singly Cabibbo-suppressed decays Λc+→pη and Λc+→pπ0 using the full Belle data sample corresponding to an integrated luminosity of 980.6 fb−1. The data were collected by the Belle detector at the KEKB e+e− asymmetric energy collider. A clear Λc+ signal is seen in the invariant mass distribution of pη. The fitted number of signal events of the Λc+→pη process is 7734±263; from this, we measure the ratio of branching fractions B(Λc+→pη)/B(Λc+→pK−π+)=[2.258±0.077(stat)±0.122(syst)]×10−2, from which we infer the branching fraction B(Λc+→pη)=[1.42±0.05(stat)±0.11(syst)]×10−3. In addition, no significant signal for Λc+→pπ0 is found, so an upper limit on the branching fraction of B(Λc+→pπ0)<8.0×10−5 at a 90% credibility level is set, more than 3 times better than the best current upper limit.
We report results from a study of the spin and parity of Ξc(2970)+ using a 980 fb−1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e− collider. The decay angle distributions in the chain...
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We report results from a study of the spin and parity of Ξc(2970)+ using a 980 fb−1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e− collider. The decay angle distributions in the chain Ξc(2970)+→Ξc(2645)0π+→Ξc+π−π+ are analyzed to determine the spin of this charmed-strange baryon. The angular distributions strongly favor the Ξc(2970)+ spin J=1/2 over 3/2 or 5/2, under an assumption that the lowest partial wave dominates in the decay. We also measure the ratio of Ξc(2970)+ decay branching fractions R=B[Ξc(2970)+→Ξc(2645)0π+]/B[Ξc(2970)+→Ξc′0π+]=1.67±0.29(stat)−0.09+0.15(syst)±0.25(IS), where the last uncertainty is due to possible isospin-symmetry-breaking effects. This R value favors the spin-parity JP=1/2+ with the spin of the light-quark degrees of freedom sl=0. This is the first determination of the spin and parity of a charmed-strange baryon.
We report the first evidence for X(3872) production in two-photon interactions by tagging either the electron or the positron in the final state, exploring the highly virtual photon region. The search is performed in ...
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We report the first evidence for X(3872) production in two-photon interactions by tagging either the electron or the positron in the final state, exploring the highly virtual photon region. The search is performed in e+e−→e+e−J/ψπ+π−, using 825 fb−1 of data collected by the Belle detector operated at the KEKB e+e− collider. We observe three X(3872) candidates, where the expected background is 0.11±0.10 events, with a significance of 3.2σ. We obtain an estimated value for Γ˜γγB(X(3872)→J/ψπ+π−) assuming the Q2 dependence predicted by a cc¯ meson model, where −Q2 is the invariant mass squared of the virtual photon. No X(3915)→J/ψπ+π− candidates are found.
We present an analysis of the exclusive B+→π+π−ℓ+νℓ decay, where ℓ represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The study exploits the full ϒ(4S) da...
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We present an analysis of the exclusive B+→π+π−ℓ+νℓ decay, where ℓ represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The study exploits the full ϒ(4S) data sample collected by the Belle detector, corresponding to 711 fb−1 of integrated luminosity. Events are selected by fully reconstructing one B meson in hadronic decay modes, subsequently determining the properties of the other B meson. We extract the signal yields using a binned maximum-likelihood fit to the missing-mass squared distribution in bins of the invariant mass of the two pions or the momentum transfer squared. We measure a total branching fraction of B(B+→π+π−ℓ+νℓ)=[22.7−1.6+1.9(stat)±3.5(syst)]×10−5, where the uncertainties are statistical and systematic, respectively. This result is the first reported measurement of this decay.
Using the entire data sample of 980 fb−1 integrated luminosity collected with the Belle detector at the KEKB asymmetric-energy e+e− collider, we present an amplitude analysis measuring the branching fractions of the ...
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Using the entire data sample of 980 fb−1 integrated luminosity collected with the Belle detector at the KEKB asymmetric-energy e+e− collider, we present an amplitude analysis measuring the branching fractions of the Cabibbo-allowed, W-exchange resonant decay Ξc0→Ξ0ϕ(→K+K−) with a polarized ϕ and the nonresonant decay via a direct process Ξc0→Ξ0K+K−. We present these measurements, relative to the normalization mode Ξ−π+, and find branching ratios B(Ξc0→Ξ0ϕ(→K+K−))(BΞc0→Ξ−π+)=0.036±0.004(stat.)±0.002(syst.) and B(Ξc0→Ξ0K+K−)B(Ξc0→Ξ−π+)=0.039±0.004(stat.)±0.002(syst.), which suggest that only minor cusping peaks occur in the combinatorial background of Ω*−→Ξ0K− due to these Ξc0 decays.
We measure the time-dependent CP violation parameters in B0→KS0KS0KS0 decays using 772×106BB¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. The ...
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We measure the time-dependent CP violation parameters in B0→KS0KS0KS0 decays using 772×106BB¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. The obtained mixing-induced and direct CP asymmetries are −0.71±0.23 (stat)±0.05 (syst) and 0.12±0.16 (stat)±0.05 (syst), respectively. These values are consistent with the Standard Model predictions. The significance of CP violation differs from zero by 2.5 standard deviations.
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