Guido Corbò

Model independent determination of the light-cone wave functions for exclusive processes

Abstract We present a method to compute, by numerical simulations of lattice QCD, the light-cone wave functions which enter exclusive processes at large momentum transfer, such as electromagnetic elastic scatterings, or exclusive semi-leptonic decays as B→π (B→ρ) and radiative decays as B→K ∗ γ . The method is based on first principles and does not require any model assumption.

Perturbative renormalization of the lowest moment operators of dis in lattice QCD

Abstract Using lattice QCD with Wilson fermions, we compute in the quenched approximation the renormalization constants of the operators entering into the Monte Carlo evaluation of the first moment of the singlet and non-singlet F 2 structure functions.

Model independent determination of the shape function for inclusive b decays and of the structure functions in DIS

Abstract We present a method to compute, by numerical simulations of lattice QCD, the inclusive semileptonic differential decay rates of heavy hadrons and the structure functions which occur in deep inelastic scattering. The method is based on first principles and does not require any model assumption. It allows the prediction of the differential rate in B semileptonic decays for values of the recoiling hadronic mass W∼ M B Λ QCD , which is in the relevant region to extract | V ub | from the end-point of the lepton spectrum in inclusive decays.

Factorization and effective theories

Abstract We prove factorization in the decay B→D (∗) + jet using the Large Energy Effective Theory. The proof is non perturbative, does not require any gauge fixing and is exact in the limit of a very narrow jet. On the other hand, it is shown that the Large Energy Effective Theory is unable to consistently describe completely exclusive processes such as for example B→D (∗) +π due to an oversimplification of transverse momentum dynamics. Therefore we present a variant of the Large Energy Effective Theory, i.e. a new effective theory for massless particles which properly takes into account transverse degrees of freedom and is the natural framework to study exclusive non-leptonic decays.

Mixing of dis operators in lattice QCD

Abstract We extend to the “unquenched” case the results of the perturbative calculation in lattice QCD with Wilson fermions of the mixing and renormalization coefficients of the operators entering into the expression of the lowest moment of the F 2 structure function. We argue that the rank two finite operator with vanishing anomalous dimension that we construct for unlike indices, is to be identified with the lattice energy-momentum tensor.

Renormalization in classical field theory

We discuss simple examples in which renormalization is required in classical field theory. The presentation is accessible to undergraduate students with a knowledge of the basic notions of classical electromagnetism.

LEADING LOGARITHMS IN FIELD THEORY

We consider the Sudakov form factor in effective theories and we show that one can derive correctly the double logarithms of the original, high-energy, theory. We show that in effective theories it is possible to separate explicitly soft and hard dynamics, these being two regimes related to velocity conserving and to velocity changing operators respectively. A new effective theory is sketched which extracts the leading collinear singularities of the full theory amplitudes. Finally, we show how all leading logarithmic effects in field theory can be obtained by means of simple effective theories, where they correspond to a renormalization effect.

FACTORIZATION IN EXCLUSIVE AND SEMI-INCLUSIVE HEAVY FLAVOR DECAYS AND EFFECTIVE THEORIES FOR MASSLESS PARTICLES

We prove factorization in the semi-inclusive decay B → D(*) + jet using the Large Energy Effective Theory (LEET). It is also shown that the LEET is unable to consistently describe exclusive processes, such as the decay B → D(*) + π(ρ), and therefore also related properties such as factorization. The reason is an oversimplification of transverse momentum dynamics. We present a variant of the LEET, i.e. a new effective theory for massless particles, the

Forces on a current loop and magnetic moment

\overline{\rm LEET}

Magnetic dipoles and electric currents

, which properly takes into account transverse momentum dynamics and is the natural framework to study exclusive nonleptonic decays. The transition from the LEET to the