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 the 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 bb¯-nucleon pentaquark bound states are discussed.
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This paper was supported by the NSF, Grant No. PHY-1402593. The work of V. P. is supported by the Russian Science Foundation, Grant No. 14-22-00281. M. V. P. is grateful to Hyun-Chul Kim and Michal Praszalowicz for fruitful discussions.
Eides, Michael I.; Petrov, Victor Yu.; and Polyakov, Maxim V., "Narrow Nucleon-ψ(2S) Bound State and LHCb Pentaquarks" (2016). Physics and Astronomy Faculty Publications. 430.