Light‐light and heavy‐light mesons in the model of QCD string with quarks at the ends

The variational einbein field method is applied to the model of the QCD string with quarks at the ends for the case of light‐light and heavy‐light mesons. Special attention is payed to the proper string dynamics. The correct string slope of the Regge trajectories is reproduced for light‐light states which comes out from the picture of rotating string. Masses of several low‐lying orbitally and radially excited states in the D, Ds, B, and Bs meson spectra are calculated and a good agreement with the experimental data as well as with recent lattice calculations is found. The role of the string correction to the interquark interaction is discussed at the example of the identification of D*′ (2637) state recently claimed by DELPHI Collaboration. For the heavy‐light mesons the standard constants used in Heavy Quark Effective Theory are extracted and compared to the results of other approaches.