Most high energy collisions can be described by a single hard scattering. By studying the single scattering, we can extract the parton distribution functions and test the short-distance dynamics of strong interactions. The normal parton distributions have the interpretation of the probability distributions to find a parton within a hadron. On the other hand, in order to study quantum correlatio...

Much of the predictive content of perturbative QCD (pQCD) treatment of the hadronic hard scattering is contained in factorization theorems [ 1]. Their purpose is to separate longfrom short-distance effects in scattering amplitudes. They supply perturbatively uncalculable long-distance effects with physics content in terms of well-defined matrix elements, which allows them to be measured experim...

This contribution describes two recent measurements of isolated photons appearing in photoproduction (measured by ZEUS) and deep inelastic scattering (measured by H1) at the ep collider HERA. 1. Introduction Isolated photons with high transverse momentum in the final state are a sensitive probe of the dynamics of the hard sub-process, since they are largely insensitive to hadronisation and frag...

The natural interpretation of deep inelastic scattering is in terms of hard scattering on QCD constituents of the target. We examine the relation between amplitudes measured in exclusive lepto-production and the quark content of the nucleon. We show that in the Bjorken limit, the natural interpretation of amplitudes measured in these hard exclusive processes is in terms of the quark content of ...

The distribution amplitude φ(x1, x2) gives the probability for finding two collinear partons with fractions x1 and x2 of the meson’s momentum [1]. It plays an important role e.g. in exclusive hard scattering processes and in non-leptonic decays of heavy mesons, since it allows one to separate a hard scattering amplitude, computed in perturbation theory, from the effect of the soft Fourier modes...

The intermediate scattering function (ISF) is measured for a colloidal hard-sphere glass as functions of the scattering vector and waiting time. For scattering vectors near the structure factor peak, we show that the ISF and the stretching index, defined at the crossover time between the fast and slow processes, depend algebraically on the waiting time. By contrast, the Debye-Waller factor is i...

We derive closed expressions for the mean and variance of the (mini-)jet multiplicity distribution in hard scattering processes at low x. Here (mini-)jets are defined as those due to initial-state radiation of gluons with transverse momenta greater than some resolution scale μR, where Λ 2 ≪ μ R ≪ Q, Λ being the intrinsic QCD scale and Q the momentum transfer scale of the hard scattering. Our re...

The collective dynamics of liquid gallium close to the melting point has been studied using inelastic x-ray scattering to probe length scales smaller than the size of the first coordination shell. Although the structural properties of this partially covalent liquid strongly deviate from a simple hard-sphere model, the dynamics, as reflected in the quasielastic scattering, are beautifully descri...

I present a unified calculation of soft-gluon corrections to hard-scattering cross sections through next-to-next-to-next-to-leading order (NNNLO). Master formulas are derived, from a threshold resummation formalism, that can be applied to total and differential cross sections for hard-scattering processes in hadron colliders. I also present numerical results for charged Higgs production at the ...