Observation of a new charmed baryon decaying to ${\mathrm{\Xi }}_c^{+}{\pi }^{-}{\pi }^{+}$

The ${\mathrm{\Xi }}_c^{+}{\pi }^{-}{\pi }^{+}$ spectrum is investigated using proton-proton collisions at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.4fb${}^{-1}$, collected by the LHCb experiment during 2016–2018. Four states are observed with high significance, and their masses and widths are measured to be \begin{align*} m[Ξ_c(2815)^{+}] &= 2816.65 \pm 0.03 \pm 0.03 \pm 0.23 ~$\text{MeV}$, Γ[Ξ_c(2815)^{+}] &= 2.07 \pm 0.08 \pm 0.12~$\text{MeV}$,\[5pt] m[Ξ_c(2923)^{+}] &= 2922.8 \pm 0.3 \pm 0.5 \pm 0.2~$\text{MeV}$, Γ[Ξ_c(2923)^{+}] &= 5.3 \pm 0.9 \pm 1.4~$\text{MeV}$,\[5pt] m[Ξ_c(2970)^{+}] &= 2968.6 \pm 0.5 \pm 0.5 \pm 0.2~$\text{MeV}$, Γ[Ξ_c(2970)^{+}] &= 31.7 \pm 1.7 \pm 1.9~$\text{MeV}$,\[5pt] m[Ξ_c(3080)^{+}] &= 3076.8 \pm 0.7 \pm 1.3 \pm 0.2~$\text{MeV}$, Γ[Ξ_c(3080)^{+}] &= 6.8 \pm 2.3 \pm 0.9~$\text{MeV}$, \end{align*} where the uncertainties are statistical, systematic, and due to the limited precision on the ${\mathrm{\Xi }}_c^{+}$ mass, respectively. The ${\mathrm{\Xi }}_c(2923{)}^{+}$ baryon is observed for the first time, and is consistent with being the isospin partner of the previously observed ${\mathrm{\Xi }}_c(2923{)}^0$ state. Most of the measured parameters are more precise than existing world averages.