Lattice study of exotic S=+1 baryon

Abstract

We propose S=+1 baryon interpolating operators, which are based on an exotic description of the antidecuplet baryon like diquark-diqaurk-antiquark. By using one of the new operators, the mass spectrum of the spin-1/2 pentaquark states is calculated in quenched lattice QCD at $\beta =6/g^2=6.2$ on a $32^3\times 48$ lattice. It is found that the $J^P$ assignment of the lowest $\Theta (uudd\bar{s})$ state is most likely $(1/2{)}^{-}$. We also calculate the mass of the charm analog of the $\Theta$ and find that the ${\Theta }_c(uudd\bar{c})$ state lies much higher than the $DN$ threshold, in contrast to several model predictions.

Comments: 4 pages, 4 figures, REVTEX4, v3:one figure added as recommended by referee, v4: version accepted for publication in PRL, increased statistics, typos corrected, references added, conclusions remain unchanged