Light-meson orbital excitations in the QCD string approach

In the framework of the QCD string approach it is shown that the spin-averaged masses M̄(nL) of all low-lying light mesons are well described using the string tension σ as the only parameter. The Regge slope αL^' and the intercept αL(0) of the Regge L trajectory for M̄(nL) are calculated analytically and turn out to be αL^'=0.80 GeV^-2 (for $L<~4)$ and αL(0)=-0.34, in good agreement with the experimental data: αLexpt^'=0.81±0.01 GeV^-2, αLexpt(0)=-0.30±0.02. To obtain this strong agreement with the data the nonperturbative quark self-energy contributions to the meson masses must be taken into account, which appear to be large and negative for small values of L, and are important for a close fit even for larger values of L. From the present analysis of the meson spectra the restriction αₛ<~0.40 on the strong coupling constant is required.