Heavy mesons in heavy quark effective theory

Elpe, Altuğ
In this thesis heavy quark effective theory is studied. Typical interaction momentum between constituents of a meson is about 300MeV where QCD is in its nonperturbative region. Although there is no solution to QCD in this region information can be obtained by using effective field theories. The heaviest quarks have mass much greater than QCD. This property is used to construct an effective field theory in the infinite mass limit by modifying the QCD Lagrangian. The residual motion and the spin interactions of the heavy quark are shown to be suppressed by the heavy quark mass. This leads to the formation of degenerate spin doublets of B and D mesons. Also it is predicted that the change in mass when the light quark flavor is changed is the same between B and D mesons. Then HQET is used to study semileptonic B to D decays upto the first order in perturbative series. In the end Vcb is calculated.