We consider exotic baryons with hidden charm as antiquark-diquark-diquark composite systems. Spin and isospin structure of such exotic states is given and masses are estimated. The data for production of pentaquarks in the reaction Λb→K−pJ/ψ are discussed. We suggest that the narrow peak in pJ/ψ spectra at 4450 MeV is antiquark-diquark-diquark state with negative parity, 5/2−(4450), while the broad bump 3/2+(4380) is the result of rescatterings in the (pJ/ψ)-channel. Positions of other pentaquarks with negative parity are estimated.
@article{arxiv.1507.07652,
title = {Pentaquarks and resonances in the $pJ/\psi$ spectrum},
author = {V. V. Anisovich and M. A. Matveev and J. Nyiri and A. V. Sarantsev and A. N. Semenova},
journal= {arXiv preprint arXiv:1507.07652},
year = {2015}
}