Masses of light mesons and analytical confinement
  Spectrum of masses of light pseudoscalar ($\pi, K, \eta, \eta'$) and vector ($\rho, K^*, \omega, \phi$) mesons can be explained on the base of the following assumptions: (1) analytical confinement (propagators of quarks and gluons are entire analytical functions of the Gaussian type), (2) mesons are bound states of quark and gluons (the Bethe-Salpeter equation in the one-gluon exchange approximation) and (3) QCD coupling constant $\alpha_s(M)$ is a monotone decreasing function of mass of a bound state $M$. The decay constants $f_\pi$ and $f_K$ are calculated. 
G. V. Efimov