Inclusive electroproduction of light hadrons with large p_T at next-to-leading order

We review recent results on the inclusive electroproduction of light hadrons at next-to-leading order in the parton model of quantum chromodynamics implemented with fragmentation functions and present updated predictions for HERA experiments based on the new AKK set.Comment: 4 pages, 5 figures, to appear in the proceedings of the XIII International Workshop on Deep Inelastic Scattering (DIS 2005

Charmonium production in two-photon collisions at next-to-leading order

We review recent results on the production of prompt charmonium in association with a hadron jet or a prompt photon in two-photon collisions at next-to-leading order in the factorization framework of nonrelativistic quantum chromodynamics.Comment: 4 pages, 2 figures, to appear in the proceedings of the XIII International Workshop on Deep Inelastic Scattering (DIS 2005

Propagator mixing renormalization for Majorana fermions

We consider a mixed system of unstable Majorana fermions in a general parity-nonconserving theory and renormalize its propagator matrix to all orders in the pole scheme, in which the squares of the renormalized masses are identified with the complex pole positions and the wave-function renormalization (WFR) matrices are adjusted in compliance with the Lehmann-Symanzik-Zimmermann reduction formalism. In contrast to the case of unstable Dirac fermions, the WFR matrices of the in and out states are uniquely fixed, while they again bifurcate in the sense that they are no longer related by pseudo-Hermitian conjugation. We present closed analytic expressions for the renormalization constants in terms of the scalar, pseudoscalar, vector, and pseudovector parts of the unrenormalized self-energy matrix, which is computable from the one-particle-irreducible Feynman diagrams of the flavor transitions, as well as their expansions through two loops. In the case of stable Majorana fermions, the well-known one-loop results are recovered.Comment: 20 pages, matches journal version. arXiv admin note: text overlap with arXiv:1308.314

Considerations concerning the generalization of the Dirac equations to unstable fermions

We discuss the generalization of the Dirac equations and spinors in momentum space to free unstable spin-$1/2$ fermions taking into account the fundamental requirement of Lorentz covariance. We derive the generalized adjoint Dirac equations and spinors, and explain the very simple relation that exists, in our formulation, between the unstable and stable cases. As an application of the generalized spinors, we evaluate the probability density. We also discuss the behavior of the generalized Dirac equations under time reversal.Comment: 7 pages, matches journal versio