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 M ¯(nL) of all low-lying light mesons are well described using the string tension s as the only parameter. The Regge slope a L and the intercept a L(0) of the Regge L trajectory for M ¯(nL) are calculated analytically and turn out to be a L50.80 GeV 22 ~for L<4) and a L(0)520.34, in good agreement with the experimental data: a L expt 8 50.8160.01 GeV 22 , a L expt(0)520.3060.02. 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 a s<0.40 on the strong coupling constant is required.