First Observation of A? plus and A?- Signals near the ?KN(I=1) Mass Threshold in Ac plus ? A? plus ? plus ?- Decay

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2023-04-12, 2023-04-12

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American Physical Society


Using the data sample of 980 fb-1 collected with the Belle detector operating at the KEKB asymmetric-energy e+e- collider, we present the results of an investigation of the Λπ+ and Λπ- invariant mass distributions looking for substructure in the decay Λc+→Λπ+π+π-. We find a significant signal in each mass distribution. When interpreted as resonances, we find for the Λπ+ (Λπ-) combination a mass of 1434.3±0.6(stat)±0.9(syst) MeV/c2 [1438.5±0.9(stat)±2.5(syst) MeV/c2], an intrinsic width of 11.5±2.8(stat)±5.3(syst) MeV/c2 [33.0±7.5(stat)±23.6(syst) MeV/c2] with a significance of 7.5σ (6.2σ). As these two signals are very close to the K̄N threshold, we also investigate the possibility of a K̄N cusp, and find that we cannot discriminate between these two interpretations due to the limited size of the data sample.



Science & Technology, Physical Sciences, Physics, Multidisciplinary, Physics, NUCLEON INTERACTIONS, LAMBDA(1405), Belle Collaboration, 5106 Nuclear and Plasma Physics, 5107 Particle and High Energy Physics, 51 Physical Sciences, 40 Engineering, 49 Mathematical sciences