Are ${\Theta }^{+}$ and the Roper resonance diquark-diquark-antiquark states?

R. D. Matheus, F. S. Navarra, M. Nielsen +2

We consider a $[ud{]}^2\bar{s}$ current in the QCD sum rule framework to study the mass of the recently observed pentaquark state ${\Theta }^{+}(1540)$, obtaining good agreement with the exper…