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 PDG). Using the Dalitz fit result, the ratio ... is measured to be ...; 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 ... is determined. In addition, the π η ′ contribution to the a0( 980 )± resonance shape is confirmed with 10.1 σ statistical significance using the three-channel Flatté model. We also measure ... . This is consistent with, and more precise than, the current world average ( 1.02 ± 0.30 ) % , deviates with a significance of more than 3 σ from the theoretical predictions of (0.51–0.92)%. (ProQuest: ... denotes formulae omited.).
We have searched for the Cabibbo-suppressed decay Λc+→ϕpπ0 in e+e− collisions using a data sample corresponding to an integrated luminosity of 915 fb−1. The data were collected by the Belle ...experiment at the KEKB e+e− asymmetric-energy collider running at or near the ϒ(4S) and ϒ(5S) resonances. No significant signal is observed, and we set an upper limit on the branching fraction of B(Λc+→ϕpπ0)<15.3×10−5 at 90% confidence level. The contribution of nonresonant Λc+→K+K−pπ0 decays is found to be consistent with zero, and the corresponding upper limit on its branching fraction is set to be B(Λc+→K+K−pπ0)NR<6.3×10−5 at 90% confidence level. We also search for an intermediate hidden-strangeness pentaquark decay Ps+→ϕp. We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of B(Λc+→Ps+π0)×B(Ps+→ϕp)<8.3×10−5 at 90% confidence level. Finally, we measure the branching fraction for the Cabibbo-favored decay Λc+→K−π+pπ0; the result is B(Λc+→K−π+pπ0)=(4.42±0.05(stat)±0.12(syst)±0.16(norm))%, which is the most precise measurement to date.
We report a search for a heavy neutral lepton (HNL) that mixes predominantly with ν τ . The search utilizes data collected with the Belle detector at the KEKB asymmetric energy e + e − collider. The ...data sample was collected at and just below the center-of-mass energies of the ϒ ( 4 S ) and ϒ ( 5 S ) resonances and has an integrated luminosity of 915 fb − 1 , corresponding to ( 836 ± 12 ) × 10 6 e + e − → τ + τ − events. We search for production of the HNL (denoted N ) in the decay τ − → π − N followed by its decay via N → μ + μ − ν τ . The search focuses on the parameter-space region in which the HNL is long-lived, so that the μ + μ − originate from a common vertex that is significantly displaced from the collision point of the KEKB beams. Consistent with the expected background yield, one event is observed in the data sample after application of all the event-selection criteria. We report limits on the mixing parameter of the HNL with the τ neutrino as a function of the HNL mass. Published by the American Physical Society 2024
We report the results of a study of B super(+/-) arrow right K super(+/) eta c and B super(+/-) arrow right K super(+/-) eta c(2S) decays followed by eta and eta (2S) decays to super(0)(KSK pi ). The ...results are obtained from a data sample containing 535 million inline image-meson pairs collected by the Belle experiment at the KEKB e super(+)e super(-) collider. We measure the products of the branching fractions inline image and inline image. Interference with the non-resonant component leads to significant model uncertainty in the measurement of these product branching fractions. Our analysis accounts for this interference and allows the model uncertainty to be reduced. We also obtain the following charmonia masses and widths: inline image, inline image, inline image, inline image.
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