6533b861fe1ef96bd12c4256

RESEARCH PRODUCT

Hidden-charm pentaquark state inΛb0→J/ψpπ−decay

subject

description

We study here the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{\ensuremath{\pi}}^{\ensuremath{-}}$ reaction in analogy to the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{K}^{\ensuremath{-}}$ one, and we note that in both decays there is a sharp structure (dip or peak) in the $J/\ensuremath{\psi}p$ mass distribution around 4450 MeV, which is associated in the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{K}^{\ensuremath{-}}$ experiment to an exotic pentaquark baryonic state, although in ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{\ensuremath{\pi}}^{\ensuremath{-}}$ it shows up with relatively low statistics. We analyze the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{\ensuremath{\pi}}^{\ensuremath{-}}$ interaction along the same lines as the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{K}^{\ensuremath{-}}$ one, with the main difference stemming from the reduced Cabibbo strength in the former and the consideration of the ${\ensuremath{\pi}}^{\ensuremath{-}}p$ final state interaction instead of the ${K}^{\ensuremath{-}}p$ one. We find that with a minimal input, introducing the ${\ensuremath{\pi}}^{\ensuremath{-}}p$ and $J/\ensuremath{\psi}p$ interaction in $S$-wave with realistic interactions, and the empirical $P$-wave and $D$-wave contributions, one can accomplish a qualitative description of the ${\ensuremath{\pi}}^{\ensuremath{-}}p$ and $J/\ensuremath{\psi}p$ mass distributions. More importantly, the peak structure followed by a dip of the experimental $J/\ensuremath{\psi}p$ mass distribution is reproduced with the same input as used to describe the data of ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}p{K}^{\ensuremath{-}}$ reaction. The repercussion for the triangular singularity mechanism, invoked in some works to explain the pentaquark peak, is discussed.