Heavy Quark Expansion con dati di QCD su reticolo

This thesis focuses on the extraction of Heavy Quark Expansion (HQE) parameters from lattice data on pseudoscalar and vector heavy-light meson masses. The lattice computation was carried out by the European Twisted Mass Collaboration (ETMC) with N_f=2+1+1 dynamical quarks with m_h that ranges from the physical charm mass up to 4 times the physical b-quark mass. The kinetic scheme with mu_s=1 GeV is employed for masses and HQE parameters. The average meson masses and the hyperfine meson mass splitting are used to extract LambdaBar, mu_pi^2, mu_G^2(m_b),rho_D^3-rho_pipi^3-rho_S^3, rho_pi G^3+rho_A^3-rho_LS^3 which are the matrix elements of operators of dimension 4, 5 and 6 of the effective Lagrangian of Heavy Quark Effective Theory (HQET). With respect to previous analysis several possible improvements have been investigated, changing the way of computing the kinetic mass of the heavy quark, considering perturbative corrections to the fitting formula, taking into account Wilson coefficients and including corrections at order O(alpha_s^3). These analyses may help in computing theoretical uncertainties on the HQE parameters and in validating analyses based on fits to semileptonic moments of B-meson decay rates. The extracted parameters play a crucial role in the inclusive determination of the Cabibbo-Kobayashi-Maskawa matrix elements |V_ub| and |V_cb|.