We perform a theoretical analysis of the Lambda(b) -> J/psi K(-)p reaction from where a recent LHCb experiment extracts a Lambda(1405) contribution in the K(-)p spectrum close to threshold and two baryon states of hidden charm in the J/psi p spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and J(P) of the experiment; concretely some states built up from the J/psi N, (D) over bar*Lambda(c), (D) over bar*Sigma(c), (D) over bar Sigma(c)* and (D) over bar*Sigma(c)* coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the K(-)p mass distribution close to threshold and the peak of the J/psi p distribution, with values of the J/psi p coupling to the resonance in line with the theoretical ones. The nontrivial matching of many properties gives support to a J(P) = 3/2(-) assignment to this state and to its nature as a molecular state mostly made of (D) over bar*Sigma(c) and (D) over bar*Sigma(c)*.

This work is partly supported by the Spanish Ministerio de Economia y Competitividad and European FEDER funds under Grants No. FIS2011-28853-C02-01, No. FIS2011-28853-C02-02, No. FIS2014-51948-C2-1-P, No. FIS2014-51948-C2-2-P, No. FPA2013-40483-P, No. FIS2014-57026-REDT and the Generalitat Valenciana in the program Prometeo Grant No. II-2014/068. We acknowledge the support of the European Community-Research Infrastructure Integrating Activity Study of Strongly Interacting Matter (HadronPhysics3, Grant No. 283286) under the Seventh Framework Programme of the EU. This work is partially funded by the grants MINECO (Spain) and ERDF (EU), Grant No. FPA2013-40483-P.

4 pages.- 2 figures

Peer reviewed