Hard processes at the TeV scale exhibit enhanced (double log) EW corrections, that need resummation in view of the high level of precision of Next Linear Colliders. The fact that the weak sector is spontaneously broken causes some peculiarities with respect to unbroken theories like QCD. For observables that are exclusive with respect to W,Z emission, some peculiar technical problems have yet t...

We consider power-like corrections in QCD which can be viewed as power surpressed infrared singularities. We argue that the presence of these singularities depends crucially on the energy resolution. In case of poor energy resolution, i.e., inclusive cross sections, there are constraints on in-frared singularities expressed by the Kinoshita-Lee-Nauenberg (KLN) theorem. We rewrite the theorem in...

We derive a formula for computing the transition rate for a process involving particles with momentum much higher than the temperature and chemical potentials in a plasma by using an effective field theory approach. We apply it to collision of charged particles with hard momentum inside a QED plasma. The Debye screening effect and the damping of a charged particle moving in QED plasma are studi...

We study the scattering of hard external particles in a heat bath in a real-time formalism for finite temperature QED. We investigate the distribution of the 4-momentum difference of initial and final hard particles in a fully covariant manner when the scale of the process, Q, is much larger than the temperature, T. Our computations are valid for all T subject to this constraint. We exponentiat...

We investigate the one-loop radiative corrections to the semileptonic decay of a charged particle at finite gauge boson mass. Extending the Bloch-Nordsieck cancellation of infrared logarithms, the subsequent non-analytic terms are also found to vanish after eliminating the pole mass in favor of a mass defined at short distances. This observation justifies the operator product expansion for incl...

The study of the ultrarelativistic plasmas in perturbation theory is plagued with infrared divergences which are not eliminated by the screening corrections. They affect, in particular, the computation of the lifetime of the elementary excitations, thus casting doubt on the validity of the quasiparticle picture. We show that, for Abelian plasmas at least, the infrared problem of the damping rat...

This report is a self-contained and comprehensive review of the physics of propagating pulses of high-intensity high-energy particle beams in pre-existing or self-generated plasmas. The first part is a systematic overview of the theory pertaining to propagation, plasma self-generation, energy/current-losses, and stability of such pulses. The second part reviews the major full-scale propagation ...