Dalitz analysis of D0 → K− π+ η decays at Belle
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Physical Review D 102 : (2020) // Article ID 012002
[EN] We present the results of the first Dalitz plot analysis of the decay D0 → K−πþη. 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 eþe− KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K¯ ð892Þ0η, K−a0 ð980Þþ, K−a2 ð1320Þþ, K¯ ð1410Þ0η, K ð1680Þ−πþ and K 2 ð1980Þ−πþ, together with Kπ and Kη S-wave components. The decays K ð1680Þ− → K−η and K 2 ð1980Þ− → K−η are observed for the first time. We measure ratio of the branching fractions, BðD0→K−πþηÞ BðD0→K−πþÞ ¼ 0.500 0.002ðstatÞ 0.020ðsystÞ 0.003ðBPDGÞ. Using the Dalitz fit result, the ratio BðK ð1680Þ→KηÞ BðK ð1680Þ→KπÞ is measured to be 0.11 0.02ðstatÞþ0.06 −0.04 ðsystÞ 0.04ðBPDGÞ; this is much lower than the theoretical expectations (≈1) made under the assumption that K ð1680Þ is a pure 13D1 state. The product branching fraction BðD0 → ½K 2 ð1980Þ− → K−η πþÞ ¼ ð2.2 þ1.7 −1.9 Þ × 10−4 is determined. In addition, the πη0 contribution to the a0 ð980Þ resonance shape is confirmed with 10.1σ statistical significance using the three-channel Flatte´ model.We also measure BðD0 → K¯ ð892Þ0ηÞ ¼ ð1.41 þ0.13 −0.12 Þ%. This is consistent with, and more precise than, the current world average ð1.02 0.30Þ%, deviates with a significance of more than 3σ from the theoretical predictions of (0.51–0.92)%.