A relativistic quark model of mesons

We propose a relativistic quantum model to describe mesons comprising a quark and an antiquark with arbitrary masses. The Dirac equations describe the quarks, and the rigid string approximation accounts for the gluon field contribution. The model fits the meson spectra well and determines the masses of the $s$-, $c$-, and $b$-quarks and the relativistic wave functions of compound mesons.