We have calculated the NLO corrections for the leading twist amplitude of the reaction γ * γ → ππ at large virtuality of the photon and at W 2 ≪ Q 2. With a simple model for the two-pion quark and gluon distribution amplitudes we have estimated that the NLO effects may reduce the leading-order amplitude by as much as 30%. We have found that besides the usual twist-2 quark and gluon operators th...

Light-front QCD is studied by the method of flow equations. Dynamical gluon mass is generated, which evolves with the cut-off according to renormalization group equation. Eliminating by flow equations the quark gluon coupling with the dynamical gluon mode, one obtains an effective interaction between quark and antiquark which exibits the Coulomb and confining singularities. The scale, which reg...

We calculate the classical gluon field of a fast projectile passing through a dense medium. We show that this allows us to calculate both the initial state gluon production in proton-nucleus collisions and the final state gluon radiation off a hard parton produced in nucleus-nucleus collisions. This unified description of these two phenomena makes the relation between the saturation scale Qs an...

We calculate the impact factor coupling a virtual photon to a gluon via a massive quark-antiquark pair at LL order, but with the imposition of the correct gluon kinematics. Exact analytical results are presented in triple Mellin space with respect to scaled Bjorken x, gluon transverse momentum and heavy quark mass. The application of these results to the calculation of approximate NLL coefficie...

We study effects of the intrinsic charm on the hadronic production of Ξcc at SELEX, Tevatron and LHC. By taking the intrinsic charm into account, the cross-section of the production at SELEX is changed significantly. In contrast, at LHC and Tevatron the change is small because the gluon-gluon fusion becomes dominant. The measured cross-section at SELEX is much larger than the prediction based o...

The large transverse momentum muon pair and W boson productions in the quark initiated coherent diffractive processes at hadron colliders are discussed under the framework of the two-gluon exchange parametrization of the Pomeron model. In this approach, the production cross sections are related to the small-x off-diagonal gluon distribution and the large-x quark distribution in the proton (anti...

We study coherent and incoherent diffractive hadron production in high-energy quarkonium–heavy nucleus collisions as a probe of the gluon saturation regime of quantum chromodynamics. Taking this process as a model for pA collisions, we argue that the coherent diffractive gluon production, in which the target nucleus stays intact, exhibits a remarkable sensitivity to the energy, rapidity, and at...

Abstract We thoroughly investigate both transverse momentum and threshold resummation effects on scalar-pseudoscalar pair production via quark-antiquark annihilation at the Large Hadron Collider QCD NLO+NLL accuracy. A factorization method is introduced to properly supplement soft-gluon (threshold) contribution from parton distribution functions resummed results ob...