Observation of a New Charmed Baryon Decaying to Ξ_{c}^{+}π^{-}π^{+}

Abstract

The Ξþ c π−πþ spectrum is investigated using proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb−1, collected by the LHCb experiment during 2016–2018. Four states are observed with high significance, and their masses and widths are measured to be m½Ξcð2815Þþ ¼ 2816.65 0.03 0.03 0.23 MeV, Γ½Ξcð2815Þþ ¼ 2.07 0.08 0.12 MeV, m½Ξcð2923Þþ ¼ 2922.8 0.3 0.5 0.2 MeV, Γ½Ξcð2923Þþ ¼ 5.30.91.4 MeV, m½Ξcð2970Þþ ¼ 2968.6 0.5 0.5 0.2 MeV, Γ½Ξcð2970Þþ ¼ 31.7 1.7 1.9 MeV, m½Ξcð3080Þþ ¼ 3076.8 0.7 1.3 0.2 MeV, Γ½Ξcð3080Þþ ¼ 6.8 2.3 0.9 MeV, where the uncertainties are statistical, systematic, and due to the limited precision on the Ξþ c mass, respectively. The Ξcð2923Þþ baryon is observed for the first time, and is consistent with being the isospin partner of the previously observed Ξcð2923Þ0 state. Most of the measured parameters are more precise than existing world averages.