The new pentaquarks in the diquark model

Pentaquark baryons are a natural expectation of an extended picture of hadrons where quarks and di-quarks are the fundamental units. The parity/mass pattern observed, when compared to that of exotic mesons, appears as the footprint of a compact five-quark structure. What has been learned from the X, Y, Zphenomenology informs about the newly found pentaquark structure and suggests further experimental tests and directions to be explored. (C) 2015 The Authors. Published by Elsevier B.V.