Narrow J{sup {pi}}=1/2{sup +},3/2{sup +}, and 3/2{sup -} states of {theta}{sup +} in a quark model with antisymmetrized molecular dynamics

The exotic baryon {theta}{sup +}(uudds) is studied with microscopic calculations in a quark model by using a method of antisymmetrized molecular dynamics. We predict that three narrow states, J{sup {pi}}=1/2{sup +}(I=0),J{sup {pi}}=3/2{sup +}(I=0), and J{sup {pi}}=3/2{sup -}(I=1) nearly degenerate with the lowest 1/2{sup -} state in the uudds system. We discuss KN decay widths and estimate them to be {gamma}<7 for the J{sup {pi}}={l_brace}1/2{sup +},3/2{sup +}{r_brace}, and {gamma}<1 MeV for the J{sup {pi}}=3/2{sup -} state. In contrast to these narrow states, the 1/2{sup -} states should be much broader. We assign the observed {theta}{sup +} as the J{sup {pi}}={l_brace}1/2{sup +},3/2{sup +}{r_brace}.