Dressed-quarks and the Roper resonance
  A Dyson-Schwinger equation calculation of the light hadron spectrum, which correlates the masses of meson and baryon ground- and excited-states within a single framework, produces a description of the Roper resonance that corresponds closely with conclusions drawn recently by EBAC. Namely, the Roper is a particular type of radial excitation of the nucleon's dressed-quark core augmented by a material meson cloud component. There are, in addition, some surprises. 
Craig D. Roberts, Ian C. Cloet, Lei Chang and Hannes L.L. Roberts
nucl-th hep-lat hep-ph nucl-ex