The pentaquark spectrum from Fermi statistics

We study compact hidden charm pentaquarks in the Born-Oppenheimer approximation, previously introduced for tetraquarks, assuming the heavy pair to be in a color octet. We show that Fermi statistics applied to the complex of the three light quarks, also in color octet, requires S-wave pentaquark ground states to consist of three octets of flavourSU(3) f, two with spin 1/2 and one with spin 3/2, in line with the observed, strangeness S = 0, -1, spectrum. Additional lines corresponding to decays into J/? + E and J/? + E are predicted. In the language of non-relativistic SU(6), ground state pentaquarks form either a 56 or a 20 representation, distinguished by presence or absence of pentaquarks decaying in the spin 3/2 decuplet, e.g. in J/? +?(++). Observation of a strangeness S = -2 or isospin I = 3/2 pentaquarks would be a clear signature of compact, QCD bound pentaquarks.