Hybrid baryons via QCD sum rules.

Abstract

Hybrid baryons, consisting of the three light quarks and a gluon, are investigated using the QCD sum rule method. We find that the mixed condensate 〈0\ensuremath{\Vert}\ensuremath{\psi}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\sigma}G\ensuremath{\psi}\ensuremath{\Vert}0〉=${\mathit{m}}_{0}^{2}$〈0\ensuremath{\Vert}\ensuremath{\psi}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\psi}\ensuremath{\Vert}0〉 plays a dominant role in hybrid baryons in contrast with the quark condensate in the nucleon case. For the standard value of ${\mathit{m}}_{0}^{2}$=0.8 ${\mathrm{GeV}}^{2}$, the mass of the lowest hybrid state is found to be approximately 1.5 GeV, about the observed mass of the Roper resonance.