Dalitz analysis of D-0 -> K- pi(+)eta decays at Belle

Abstract

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−a0ð980Þþ, K−a2ð1320Þþ, K¯ ð1410Þ0η, Kð1680Þ−πþ and K 2ð1980Þ−πþ, together with Kπ and Kη S-wave components. The decays Kð1680Þ− → K−η and K 2ð1980Þ− → 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 BðKð1680Þ→KηÞ BðKð1680Þ→KπÞ is measured to be 0.11 0.02ðstatÞ þ0.06 −0.04 ðsystÞ 0.04ðBPDGÞ; this is much lower than the theoretical expectations (≈1) made under the assumption that Kð1680Þ is a pure 13D1 state. The product branching fraction BðD0 → ½K 2ð1980Þ− → K−η πþÞ¼ð2.2þ1.7 −1.9 Þ × 10−4 is determined. In addition, the πη0 contribution to the a0ð980Þ resonance shape is confirmed with 10.1σ statistical significance using the three-channel Flatt´e model. We also measure BðD0 → K¯ ð892Þ0ηÞ¼ð1.41þ0.13 −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)%.