$Θ^+$ in a chiral constituent quark model and its interpolating fields

Abstract

The recently discovered pentaquark $Θ^+$ is described within the chiral constituent quark model. Within this picture the flavor-spin interaction between valence quarks inverts the $(1s)^4$ and $(1s)^3(1p)$ levels of the four-quark subsystem and consequently the lowest-lying pentaquark is a positive parity, I=0, J=1/2 state of the flavor antidecuplet, similar to the soliton model prediction. Contrary to the soliton model, however, the quark picture predicts its spin-orbit partner with $J=3/2$. Different interpolating fields intended for lattice calculations of $Θ^+$ are constructed, which have a maximal overlap with this baryon if it is indeed a quark excitation in the 5Q system.