The Sivers mechanism for the single-spin asymmetry in unpolarized lepton scattering from a transversely polarized nucleon is driven by the orbital angular momentum carried by its quark and gluon constituents, combined with QCD final-state interactions. Both quark and gluon mechanisms can generate such a single-spin asymmetry, though only the quark mechanism can explain the small single-spin asy...

The running coupling constant can be estimated by computing gluon twoand three-point Green functions from the lattice. Computing in lattice implies working in a fixed gauge sector (Landau). An source of systematic uncertainty is then the contribution of non gauge-invariant condensates, as 〈A〉, generating power corrections that might still be important at very high energies. We study the impact ...

We calculate the equal-time transverse gluon propagator in Coulomb gauge QCD using a SU(3) quenched lattice gauge simulation on large lattices, up to 11 [fm4]. We find that the equal-time gluon propagator shows scaling violation; namely, the data for different lattice spacings do not fall on top of one curve. This problem is cured by discarding data at large momenta, which suffer from discretiz...

A semi-perturbative calculation of the ghost-gluon vertex in Landau gauge YangMills theory in four and three Euclidean space-time dimensions is presented. Nonperturbative gluon and ghost propagators are employed, which have previously been calculated from a truncated set of Dyson–Schwinger equations and which are in qualitative and quantitative agreement with corresponding lattice results. Our ...

We discuss QCD condensate contributions to the gluon propagator both in the fixedpoint gauge and in covariant gauges for the external QCD vacuum gluon fields with the conclusion that a covariant gauge is essential to obtain a gauge invariant QCD vacuum energy density difference and to retain the unitarity of the quark scattering amplitude. The gauge-invariant QCD condensate contributions to the...

We consider QCD corrections to Higgs boson production through gluon–gluon fusion in hadron collisions. Using the recently evaluated [14]two-loop amplitude for this process and the corresponding factorization formulae [15, 16, 17, 18] describing soft-gluon bremsstrahlung at O(α2 S), we compute the soft and virtual contributions to the next-to-next-to-leading order cross section. We also discuss ...