We interpret the newly discovered pentaquark Pc(4450) as a bound state of charmonium ψ(2S) and the nucleon. The binding potential is due to charmonium-nucleon interaction that in the heavy quark approximation is proportional to the product of the charmonium chromoelectric polarizability and the nucleon energy-momentum distribution. We use the large Nc expansion to estimate the quarkonium polarizability and calculate the nucleon properties in the framework of the mean-field picture of light baryons. Two almost degenerate states JP=(1/2)− and JP=(3/2)− are predicted at the position of the Pc(4450) pentaquark. We find that the nucleon-ψ(2S) bound state has a naturally narrow width in the range of tens of MeV. The unitary multiplet partners of the Pc(4450) pentaquark and the generalization to bbˉ-nucleon pentaquark bound states are discussed.
@article{arxiv.1512.00426,
title = {Narrow Nucleon-$\psi(2S)$ Bound State and LHCb Pentaquarks},
author = {Michael I. Eides and Victor Yu. Petrov and Maxim V. Polyakov},
journal= {arXiv preprint arXiv:1512.00426},
year = {2016}
}