Masses and magnetic moments of exotic fully heavy pentaquarks

Inspired by the observation of a resonant state X(6600) of fully charm tetraquark by theCMSexperiment of LHCb Collaboration in double J/. decay channel, we perform a systematical study of all configurations of fully heavy pentaquarks P(Q1Q2Q3Q4 (Q) over bar)5 ( Qi = c, b, i = 1, 2, 3, 4, 5) in their ground states in unified framework of MIT bag model. The color-spin wavefunctions of pentaquarks, classified via Young tableau and presented in terms of the Young-Yamanouchi bases, are used to computemasses and magnetic moments of fully heavy pentaquarks via numerical variational method, predicting a set of masses ranging from 8.229 GeV for the P-cccc (c) over bar to 24.770 GeV for the P-bbbb (b) over bar. Combining with computed masses of fully heavy mesons and baryons, we find that masses of fully heavy hadrons(mesons, baryons, tetraquarks and pentaquarks) with identical flavor rise almost linearly with the number of valence quarks in hadrons, being consistent with the heavy quark symmetry in the heavy-quark limit.