We report on the extraction of the higher twist contributions to F2 and R = σL/σT from global NLO and NNLO QCD fits to lepton nucleon scattering data over a wide range of Q 2. The NLO fits require both target mass and higher twist contributions at low Q 2. However, in the NNLO analysis, the data are described by the NNLO QCD predictions (with target mass corrections) without the need for any si...

Theoretical predictions show that at low values of Bjorken x the spin structure function, g1 is influenced by large logarithmic corrections, ln (1/x), which may be predominant in this region. These corrections are also partially contained in the NLO part of the standard DGLAP evolution. Here we calculate the non-singlet component of the nucleon structure function, g 1 = g 1 − g 1 , and its firs...

Theoretical predictions show that at low values of Bjorken x the spin structure function is influenced by large logarithmic corrections, ln(1/x), which may be predominant in this region. These corrections are also partially contained in the NLO part of the standard DGLAP evolution. Here we calculate the non-singlet component of the nucleon structure function, g 1 = g 1 − g 1 , and its first mom...

A Monte Carlo at next-to-leading order (MC@NLO) has been constructed for the production of heavy quark flavours in photoproduction. As such, it is the first Monte Carlo event generator with next-to-leading order (NLO) accuracy for a process in lepton hadron scattering. In order to construct such an MC@NLO, the matrix element for the process has to be calculated at NLO and then be matched with a...

Nuclear parton distribution functions (NPDFs) are determined by a global analysis of experimental measurements on structure-function ratios FA 2 /F A 2 and Drell-Yan cross section ratios σ A DY /σA ′ DY , and their uncertainties are estimated by the Hessian method. The NPDFs are obtained in both leading order (LO) and next-to-leading order (NLO) of αs. As a result, valence-quark distributions a...

Abstract: We present the exact next-to-leading order (NLO) QCD corrections to dijet production at the LHC via quark contact interactions, with different color and chiral structures induced from new physics. Following the recent analysis of quark compositeness search at the LHC, we find that the NLO QCD corrections can lower the dijet cross sections by several tens percent, depending on the theo...

We study the effect of scheme dependence upon the NLO QCD analysis of the world data on polarized DIS. The reliability of an analysis at NLO is demonstrated by the consistency of our polarized densities with the NLO transformation rules relating them to each other. We stress the importance of the chiral JET scheme in which all the hard effects are consistently absorbed in the Wilson coefficient...

We extend a recent global analysis of nucleon parton distributions carried out at nextto-leading order (NLO) in the MS scheme to provide distributions in the so-called DIS scheme. We pay particular attention to the translation of the heavy quark distributions in going from the MS to the DIS scheme. We repeat the global analysis at leading order (LO) and comment on the major effects produced whe...

We present a new analysis of the helicity parton distributions of the nucleon. The analysis takes into account the available data from inclusive and semi-inclusive polarized deep inelastic scattering, as well as from polarized proton-proton (p-p) scattering at RHIC. For the first time, all theoretical calculations are performed fully at next-to-leading order (NLO) of perturbative QCD, using a m...