摘要

We present one reduction of the Bethe - Salpeter equation for the bound states composed of two off-mass-shell constituents. Both the relativistic effects and the virtuality effects can be considered in the obtained spinless virtuality distribution equation. The eigenvalues of the spinless virtuality distribution equation are perturbatively calculated and the bound states e(+)e(-), mu(+)mu(-), tau(+)tau(-), mu(+)e(-), and tau(+)e(-) are discussed.