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A Study of Excited Charm-Strange Baryons with Evidence for new Baryons Ξ_c(3055)^+ and Ξ_c(3123)^+

We present a study of excited charm-strange baryon states produced in $e^+e^-$ annihilations at or near a center-of-mass energy of $10.58\mathrm{Ge\kern -0.1em V}$, in a data sample with an integrated luminosity of $384 fb^{-1}$ recorded with the BABAR detector at the PEP-II $e^+e^-$ storage rings at the Stanford Linear Accelerator Center. We study strong decays of charm-strange baryons to $Λ_c^+K^0_{\scriptscriptstyle S}$, $Λ_c^+K^-$, $Λ_c^+K^-π^+$, $Λ_c^+K^0_{\scriptscriptstyle S}π^-$, $Λ_c^+K^0_{\scriptscriptstyle S}π^-π^+$, and $Λ_c^+K^-π^+π^-$. This study confirms the existence of the states $Ξ_c(2980)^+$, $Ξ_c(3077)^+$, and $Ξ_c(3077)^0$, with a more accurate determination of the $Ξ_c(2980)^+$ mass and width. We also present evidence for two new states, $Ξ_c(3055)^+$ and $Ξ_c(3123)^+$, decaying through the intermediate resonant modes $Σ_c(2455)^{++}K^-$ and $Σ_c(2520)^{++}K^-$, respectively. For each of these baryons, we measure the yield in each final state, determine the statistical significance, and calculate the product of the production cross-section and branching fractions. We also measure the masses and widths of these excited charm-strange baryons.