Andrzej J. Buras

The Delta I = 1/2 Rule in the Large N Limit

The large-N limit is used to obtain a consistent picture of the K → ππ matrix elements. It is confirmed that the dominant Q6 penguin matrix elements are enhanced by an order of magnitude compared to those of the current-current operators and that this result is consistent with chiral perturbation theory. An additional enhancement of the penguin contributions is identified with respect to standard estimates which comes from an incomplete GIM cancellation above the charm quark mass. Performing the short-distance analysis to first nontrivial order in 1/N its validity and simplicity is demonstrated. Encouraging results are obtained for A(K → ππ) amplitudes and it is pointed out that further improvements can be obtained through the inclusion of the low-energy evolution which necessarily must be done in a meson rather than a quark picture.

Seven Topics in Perturbative QCD

The following topics of perturbative QCD are discussed: (1) deep inelastic scattering; (2) higher order corrections to e/sup +/e/sup -/ annihilation, to photon structure functions and to quarkonia decays; (3) higher order corrections to fragmentation functions and to various semi-inclusive processes; (4) higher twist contributions; (5) exclusive processes; (6) transverse momentum effects; (7) jet and photon physics.

Simple formulae for higher-order asymptotic freedom corrections

Abstract We present simple formulae for the next-to-the-leading-order asymptotic freedom corrections to the moments of the non-singlet and the singlet combinations of the deep-inelastic structure functions for electron, muon and neutrino scattering.

Quantum chromodynamics and deep‐inelastic scattering

Moments of deep‐inelastic structure functions, parton distributions and parton fragmentation functions are discussed in the context of Quantum Chromodynamics with particular emphasis put on higher order corrections. A brief discussion of higher twist contributions is also given.

Topics in Perturbative QCD Beyond the Leading Order

Quantum Chromodynamics (QCD) is the most promising candidate for a theory of strong interactions.