JetViP is a computer program for the calculation of inclusive singleand dijet cross sections in eP and eγ-scattering in NLO QCD. The virtuality of the photon, radiated by the incoming electron, can be chosen in a continuous range, reaching from photoproduction into deep inelastic scattering. The various contributions to the full jet cross section, including the resolved photon contributions, ar...

I present some comments on the partonic interpretation of the HERA data on the proton structure function. The effects of the resummation of the leading and next-to-leading lnx-contributions are discussed. A new factorization scheme, in which these resummation effects are absorbed into a steep redefinition of the gluon density, is introduced and its (possible) interpretation and phenomenological...

We show that QCD observables defined as infraredand collinear-safe, according to the usual Sterman-Weinberg criteria, can nevertheless be infinite at accessible points inside phase space, to any finite order of perturbation theory. Infrared finiteness is restored after resummation of divergent terms to all orders. The resulting characteristic structure, which we call a Sudakov shoulder, represe...

We reexamine the top quark production cross section at the Tevatron and LHC, in the light of recent progress on the resummation of logarithmic soft gluon corrections. We find that resummation effects are much smaller than previously thought. We also compute Coulombic threshold effects, and find them negligible. We update the discussion of uncertainties due to scale dependence, the value of the ...

We present low–energy theorems for the calculation of loop amplitudes with external scalar or pseudoscalar Higgs bosons which are light compared to the loop particles. Starting from existing lowest–order versions of these theorems, we show how their applicability may be extended to the two–loop level. To illustrate the usefulness of these theorems, we discuss a number of applications to Higgs p...

We present some evidence that in lattice gauge theory the condensate contains a non-perturbative contribution proportional to Λ, the square of the physical scale. This result is based on an analysis of the Wilson loop plaquette expectation from Monte Carlo simulations and its perturbative expansion computed to eight loops. The analysis is not fully conclusive since the calculations are done on ...