Strange tribaryons as nona-quark states

Strange tribaryons as nona-quark (nine quark) states are studied in an attempt to describe the S = -1 resonance S⁰ (3115) recently discovered in the reaction K^- + ⁴He → S⁰ + p. We have identified S⁰ (3115) as a member of a flavor 27-plet, specifically, (F_flavor, I_isospin, J_spin) = (27, 1, 1/2) or (27, 1, 3/2). We investigate the mass splittings of the nona-quark system from the point of view of the color-magnetic interaction and the flavor SU_F (3) breaking. The color-magnetic interaction between quarks favors small multiplets in flavor and spin, which leads to the natural explanation that I = 1 is the lowest state among the S = -1 tribaryons with J = 1/2. Classification of the S⁺ state recently reported as well as possible locations of other light strange tribaryons, such as (10*, 0, 3/2) with S = -1, (8, 1/2, 1/2) with S = -2, and (1, 0, 3/2) with S = -3, is also studied.