Exotic dibaryons with a heavy antiquark

We discuss the possible existence of exotic dibaryons with a heavy antiquark, being realized as three-body systems, D¯(⁎)NN and B(⁎)NN. These are genuinely exotic states with no quark-antiquark annihilation. We consider the heavy quark spin and chiral symmetries, and introduce the one pion exchange potential between a D¯(⁎) (B(⁎)) meson and a nucleon N. As for the NN interaction, we employ the Argonne v8′ potential. By solving the coupled-channel equations for PNN and P⁎NN (P(⁎)=D¯(⁎) and B(⁎)), we find bound states for (I,JP)=(1/2,0−) as well as resonant states for (I,JP)=(1/2,1−) both in D¯(⁎)NN and B(⁎)NN systems. We also discuss the heavy quark limit, and find that the spin degeneracy is realized in the bound states with (I,JP)=(1/2,0−) and (1/2,1−).