EXOTIC BARYONS
INSPIRE search

${{\boldsymbol P}_{{c}}{(4380)}^{+}}$

A resonance seen in ${{\mathit \Lambda}_{{b}}^{0}}$ $\rightarrow$ ${{\mathit P}_{{c}}^{+}}{{\mathit K}^{-}}$ , then ${{\mathit P}_{{c}}}$ $\rightarrow$ ${{\mathit J / \psi}}{{\mathit p}}$ , with a significance of 9 standard deviations. The ${{\mathit J / \psi}}{{\mathit p}}$ quark content is ${{\mathit u}}{{\mathit u}}{{\mathit d}}{{\mathit c}}{{\overline{\mathit c}}}$ , a pentaquark. See also the ${{\mathit P}_{{c}}{(4450)}^{+}}$. In the best amplitude fit, the two states have opposite parity, one having $\mathit J = 3/2$, the other $\mathit J = 5/2$. Extraction of the pentaquark signals requires some understanding of the dominant ${{\mathit K}^{-}}{{\mathit p}}$ background. AAIJ 2015P used a model-dependent approach. AAIJ 2016AG reanalyzed the data making minimal assumptions about the ${{\mathit K}^{-}}{{\mathit p}}$ background, and thus confirmed the strong significance of the pentaquark signals.
${{\mathit P}_{{c}}{(4380)}^{+}}$ MASS   $4380 \pm30$ MeV 
${{\mathit P}_{{c}}{(4380)}^{+}}$ WIDTH   $205 \pm90$ MeV 
$\Gamma_{1}$ ${{\mathit J / \psi}}{{\mathit p}}$ seen741