# Observation of a Narrow Pentaquark State, ${P}_{c}\left(4312{\right)}^{+}$, and of the Two-Peak Structure of the ${P}_{c}\left(4450{\right)}^{+}$

05 June 2019

Abstract: A narrow pentaquark state, ${P}_{c}\left(4312{\right)}^{+}$, decaying to $J/\psi p$, is discovered with a statistical significance of $7.3\sigma$ in a data sample of ${\Lambda }_{b}^{0}\to J/\psi p{K}^{-}$ decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The ${P}_{c}\left(4450{\right)}^{+}$ pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, ${P}_{c}\left(4440{\right)}^{+}$ and ${P}_{c}\left(4457{\right)}^{+}$, where the statistical significance of this two-peak interpretation is $5.4\sigma$. The proximity of the ${\Sigma }_{c}^{+}{\overline{D}}^{0}$ and ${\Sigma }_{c}^{+}{\overline{D}}^{*0}$ thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states.

Published in: Physical Review Letters 122 (2019)