Quark-antiquark composite systems: The Bethe-Salpeter equation in the spectral-integration technique in the case of different quark masses

The Bethe-Salpeter equations for quark-antiquark composite systems with different quark masses, such as q (s) over bar (with q = u,d), q (Q) over bar, and s (Q) over bar (with Q = c, b), are written in terms of spectral integrals. For mesons characterized by the mass M, spin J, and radial quantum number n, the equations are written for the (n, M-2) trajectories with fixed J. The mixing between states with different quark spin S and angular momentum L is also discussed. (c) 2005 Pleiades Publishing, Inc.