Gluelump model with transverse constituent gluons

We show that C-odd gluelumps can be successfully described as bound states of a single transverse constituent gluon evolving in the flux-tube-like potential generated by a static color-octet source. The use of a helicity degree of freedom rather than a spin one for the constituent gluon forbids the states that are not observed in lattice QCD. Our model leads to a gluelump mass spectrum in remarkable agreement with the available lattice data provided that an additional parity-splitting mass term is introduced. We argue that such a term is due to instanton-induced interactions in gluelumps.