Tetraquarks, pentaquarks and dibaryons

The discovery of two pentaquarks by LHCb has reinforced the case of exotic hadrons, which have diquarks and antidiquarks as basic units. I review i) the cases studied until know, the so-called XYZ and pentaquark states, ii) the theoretical basis for this concept and iii) the implications for the existence of further states, in particular with baryon number equal to two (dibaryons)