Relativistic exchange current corrections to the impulse approximation in low and intermediate energy neutrino–nucleus scattering are presented assuming non–vanishing strange quark form factors for constituent nucleons. Two–body exchange current operators which treat all SU (3) vector and axial currents on an equal footing are constructed by generalizing the soft–pion dominance method of Chemto...

I describe some insight obtained from a lattice calculation on the possibility that the light scalar mesons are q̄2q2 states rather than q̄q. First I review some general features of q̄2q2 states in QCD inspired quark models. Then I describe a lattice QCD calculation of pseudoscalar meson scattering amplitudes, ignoring quark loops and quark annihilation, which finds indications that for sufficient...

The determination of the strange quark contribution to the nucleonic axial and vector weak currents has raised large and continuous interest in theoretical and experimental physics, especially after the measurements of the polarised structure function g 1 of the proton, which indicated a non–zero contribution of the strange quark to the proton spin. In recent years, intermediate energy physics ...

We evaluate heavy-quark (HQ) transport properties in a quark-gluon plasma (QGP) within a Brueckner many-body scheme employing interaction potentials extracted from thermal lattice QCD. The in-medium T matrices for elastic charm- and bottom-quark scattering off light quarks in the QGP are dominated by attractive meson and diquark channels which support resonance states up to temperatures of ~1.5...

We review the resummation of threshold logarithms for heavy quark, dijet, direct photon, and W boson production cross sections in hadronic collisions. Beyond leading logarithms the resummed cross section is sensitive to the color exchange in the hard scattering. The resummation is formulated at next-to-leading logarithmic or higher accuracy in terms of anomalous dimension matrices which describ...

In Leading Order (LO) prompt photons originating in the hard interaction between two partons are produced mainly via quark-gluon Compton scattering (qg → qγ) or quark–anti-quark annihilation (qq̄ → gγ). Studies of direct photons with large transverse momenta, pγT , provide precision tests of perturbative QCD (pQCD) as well as information on the distribution of partons within protons, particularl...

We assess transport properties of heavy quarks in the Quark-Gluon Plasma (QGP) using static heavy-quark (HQ) potentials from lattice-QCD calculations in a Brueckner many-body T -matrix approach to evaluate elastic heavy-quark-light-quark scattering amplitudes. In the attractive meson and diquark channels resonance states are formed for temperatures up to ∼1.5Tc, increasing pertinent drag and di...

A set of general relations between the spin-independent and spin-dependent potentials of heavy quark and anti-quark interactions are derived from reparameterization invariance in the Heavy Quark E ective Theory. It covers the Gromes relation and includes some new interesting relations which are useful in understanding the spin-independent and spin-dependent relativistic corrections to the leadi...

One loop corrections to the coupling of the reggeized gluon to quarks are calculated in QCD. Combining this result with the known corrections to the gluon-gluon-reggeon vertex, we check the self-consistency of the representation of the amplitudes with gluon quantum numbers and negative signature in the t-channel in terms of Regge pole contribution. 1. Introduction Since a long time it has been ...

In the Drell-Yan process a quark-antiquark pair is annihilated to a virtual photon, which produces lepton pairs. The corresponding cross section contains a contribution from quarks of different chirality: a quark originating from one nucleon may return to this nucleon in the squared scattering amplitude with its chirality flipped. This is possible because the intermediate photon does not rememb...