Heavy-quark exotics

The heavy quarks $c$ and $b$ stabilize exotic meson $(qq\bar q \bar q)$ and baryon $(qqqq \bar q)$ states. We discuss work with M. Karliner on molecules containing $c \bar c$ and $b \bar b$; the first doubly charmed baryon; isospin splittings; $\Xi_{cc}^+ = ccd$ and $\Omega_{cc} = ccs$ masses; lifetimes; tetraquarks stable under strong and electromagnetic decay; excited $\Omega_{c}$ states; and P-wave excitation energies.