Ablikim, M.Achasov, M.N.Adlarson, P.Çetin, Serkant AliKolcu, Onur BuğraUman, Igor2025-04-182025-04-182025Ablikim, M., Achasov, M. N., Adlarson, P., Afedulidis, O., Ai, X. C., Aliberti, R., ... & Huang, K. X. (2025). Observation of Λ c+→ Λ a 0 (980)+ and Evidence for Σ (1380)+ in Λ c+→ Λ π+ η. Physical Review Letters, 134(2), 021901.00319007http://dx.doi.org/10.1103/PhysRevLett.134.021901https://hdl.handle.net/20.500.12713/6962Based on 6.1 fb-1 of e+e- annihilation data collected at center-of-mass energies from 4.600 to 4.843 GeV with the BESIII detector at the BEPCII collider, a partial wave analysis of Λc+→Λπ+η is performed, and branching fractions and decay asymmetry parameters of intermediate processes are determined. The process Λc+→Λa0(980)+ is observed for the first time, and evidence for the pentaquark candidate ς(1380)+ decaying into Λπ+ is found with statistical significance larger than 3σ with mass and width fixed to theoretical predictions. The branching fraction product B[Λc+→Λa0(980)+]B[a0(980)+→π+η] is determined to be (1.05±0.16stat±0.05syst±0.07ext)%, which is larger than theoretical calculations by 1-2 orders of magnitude. Here the third (external) systematic is from B(Λc+→Λπ+η). Finally, we precisely obtain the absolute branching fraction B(Λc+→Λπ+η)=(1.94±0.07stat±0.11syst)%. © 2025 authors. Published by the American Physical Society.eninfo:eu-repo/semantics/openAccessAsymmetry ParameterBranching FractionsCenter-of-mass EnergiesStatistical SignificanceTheoretical CalculationsCenE+e- AnnihilationArticle1342399138122-s2.0-8521594789410.1103/PhysRevLett.134.021901Q1