Charmonium in lattice QCD and the nonrelativistic quark model

We compare the results of a numerical lattice QCD calculation of the charmonium spectrum with the structure of a general nonrelativistic potential model. To achieve this we form the nonrelativistic reduction of derivative-based fermion bilinear interpolating fields used in lattice QCD calculations and compute their overlap with $c\overline{c}$ meson states at rest constructed in the nonrelativistic quark model, providing a bound-state model interpretation for the lattice data. Essential gluonic components in the bound states, usually called hybrids, are identified by considering interpolating fields that involve the gluonic field-strength tensor and which have zero overlap onto simple $c\overline{c}$ model states.