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) over bar (nL) of all low-lying light mesons are well described using the string tension sigma as the only parameter. The Regge slope alpha(L)(') and the intercept alpha(L)(0) of the Regge L trajectory for (M) over bar (nL) are calculated analytically and turn out to be alpha(L)(')=0.80 GeV-2 (for Lless than or equal to4) and alpha(L)(0)=-0.34, in good agreement with the experimental data: alpha(L expt)(')=0.81+/-0.01 GeV-2, alpha(L expt)(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 alpha(s)less than or equal to0.40 on the strong coupling constant is required.